Batteries Demystified: Ramesh Natarajan Introduces You to the World of Batteries 9789390661695, 9390661692

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Introduces You To The World Of Batteries

Disclaimer This book has been published with all reasonable efforts taken to make the material error-free after the consent of the author. This book is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, resold, or otherwise circulated without the copyright owner's prior written consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser and without limiting the rights under copyright reserved above, no part of this publication maybe reproduced, stored in or introduced into a retrieval system or transmitted in any form or by any other means without the permission of the copyright owner.

Registered Office- 907-Sneh Nagar, Sapna Sangeeta Road, Agrasen Square, Indore – 452001 (M.P.), India Website: http://www.wingspublication.com Email: [email protected] First Published by WINGS PUBLICATION 2022 Copyright © Ramesh Natarajan Title : BATTERIES DEMYSTIFIED All Rights Reserved. ISBN : 978-93-90661-69-5 LIMITS OF LIABILITY/DISCLAIMER OF WARRANTY The Author of this book is solely responsible and liable for its content including but not limited to the views, representations, descriptions, statements, information, opinions and references. The information presented in this book is solely compiled by the Author from sources believed to be accurate and the Publisher assumes no responsibility for any errors or omissions. The information is not intended to replace or substitute professional advice. The Content of this book shall not constitute or be construed or deemed to reflect the opinion or expression of the Publisher. Publisher of this book does not endorse or approve any content of this book or guarantee the reliability, accuracy or completeness of the content published herein and do not make any representations or warranties of any kind, express or implied, including but not limited to the implied warranties of merchantability, fitness for a particular purpose. The Publisher shall not be held liable whatsoever for any errors, omissions, whether such errors or omissions result from negligence, accident, or any other cause or claims for loss or damages of any kind, including without limitation, indirect or consequential loss or damage arising out of use, inability to use, or about the reliability, accuracy or sufficiency of the information contained in this book. All disputes are subject to Indore (M.P.) jurisdiction only.

Dedicated to my parents This book is undoubtedly a result of their blessings… My mother, Mrs. Mohana Natarajan, is no more. She did not have any formal educational degree. She was one amongst a few persons whom I adored for various reasons. She acquired all the necessary knowledge she wanted in her lifetime - despite the lack of formal education. She used technology relevant to the times to further her goal of learning and I am fortunate to have hopefully imbibed a lot of her wisdom and innovative thoughts. How I wish she had lived to see this day! My father, Mr. K V Natarajan, is a veteran of the Indian battery industry. His lifetime achievements are difficult to emulate. I have always been a keen admirer of his work ethic and his systematic method of working. I have been fortunate to have had the opportunity to learn a lot from him. He is 92 years old now and his passion for work and his selflessness continue to be a source of inspiration for me.

Acknowledgements My sincere thanks are due, to my wife, Nalini, who has ensured that I can pursue my career and passion for work in an unhindered and devoted manner. This has provided me with the strength and courage to explore uncharted territories all through my life. Her assurance at all stages of my life has made our over 30 years of togetherness seem like a breeze. She has always been and continues to be a tremendous source of motivation for me. She has ensured that all family-related activities, especially as regards our children, during their growing up years - were handled by her, with due care and necessary tenderness. If not for this cooperation from her, all through my career and especially in the last few months, when I started this writing activity - I would not have ventured into this project. I must thank my son Rahul, who has contributed a lot by adding relevant photos and has suggested important changes to improve the aesthetics and readability of this book. His suggestions to make the book user-friendly have helped me to stick to my goal of keeping the book simple and hopefully interesting for the layman. He has been a source of immense strength to me and I am sure he will scale greater heights. The seed in the form of an idea.... to pen this book.... was planted by my daughter Priya. My son in law Aditya, asking me regularly about the progress of the book, has ensured that I work with single-minded devotion and adhere to a timeline. Their ideas and ardent support is something I will always cherish. Last but not least, I would like to thank Mr. Bejoy Peter, my media advisor, for his help in publishing this book.

Preface Congratulations! You are holding in your hand a book, which I hope, will demystify the subject of lead acid batteries for you. I have tried my best to keep the language simple and not use any jargon or complicated chemical formulae, which can confuse the reader and encourage the skipping of pages or chapters. Battery manufacturing...as a subject is evincing much interest in recent times due to the advent of electric vehicles and due to the environmental activists' push for renewable energy as an alternative source of power. The "Work from Home" culture has also compelled many people to install UPS systems in their homes to ensure the availability of uninterrupted power. Thus, batteries have touched everyone's lives in one way or the other. The manufacturing of batteries necessitates some understanding of metallurgy, chemistry, mechanical engineering and electrical engineering calculations in addition to chemical engineering. The subject of batteries, however, is even nowadays taught at a very superficial level in colleges. Over the years, I have been approached by professors and students of various engineering colleges with a request that I help them understand the subject of batteries better. A few from the battery manufacturing fraternity have also been encouraging me to share my knowledge and experience. With over 42 years of experience.... encompassing design, process, production, quality assurance, testing and QMS in addition to working on large projects to set up lead acid battery plants.....I realised that I need to give back something to society in terms of my experience by sharing my

knowledge on this topic. I started in a small way by answering the various queries raised on Quora. I am happy to note that my answers on Quora have received over 80000 views as on date in a very short period of time. The ‘Up votes’, ‘Comments’ and ‘Shares’ of my answers have also been a source of encouragement for me. As I mentioned at the beginning of this interaction with you, I want to demystify the subject of batteries for you - the battery user. I do not want you to run through the pages without understanding just because you have got this book. Hence this book has basic data only. If you have bought this book, I hope you will find it useful enough so that it delivers some value to you. If you have been gifted this book by a wellwisher, I can only say that you are lucky to have such people in your circle of friends and family. Enjoy the reading experience and do send me your queries pertaining to lead acid batteries and send me your feedback about this book on, - [email protected].

Prologue The development of the human species, from the days of being a caveman until the date of establishing his supremacy by hunting down other animals for food, has been chronicled down the ages. Once human beings learnt to survive on a day to day basis, the natural progression was to store for future needs. Storage of energy, as a necessity for use as and when required in the future, was also a similar need. The birth of lead acid batteries to store energy was a landmark invention in the evolution of mankind. The first version of the Lead Acid Battery was invented by the Frenchman Gaston Plante in the year 1860. This was the most successful secondary battery and continues to be the most practical & widely used safe battery of robust design till date. Lead Acid Batteries are highly recyclable, making it the lowest environmental footprint energy storage technology. Plante used corroded lead foils to form the active material and contained the electrolyte in a glass jar. He separated the lead foils to prevent shorting by inserting a rubber strip in between these foils. With a view to improving the battery capacity further, Faure coated the lead foils with lead oxide. This enhanced commercial usage and provided wider acceptance of the technology. The success of this was improved upon by replacing the lead foils with perforated lead mesh, i.e. a grid structure to hold the paste. This was done in the year 1881 by Volckmar. Sellon, in the same year 1881, worked on these lead grids and added Antimony which hardened the grid and improved the mechanical strength. Further improvements in subsequent years by Brush, Tudor & Lucas

continued. In the year 1890, Phillipart designed the tubular battery with individual ring-type construction. Subsequent years witnessed a lot of research & developments in alloys and paste formulations, which led to improvements in battery life and capacity. The automation of processes once the technology was standardised helped industries to manufacture consistent quality products with a much better life. The Lead Acid Batteries became very popular due to its various applications in automobiles, trains, aircrafts, telecom sector, material handling applications, golf carts, scrubbers, space research, electric vehicles, nuclear power stations, solar photovoltaic systems, UPS systems, home inverters etc. etc. The challenge faced by the users was in terms of the maintenance of these batteries. This was satisfactorily addressed by the industry by introducing maintenance free batteries, having, Absorptive Glassmat Separators (AGM) or GEL mixed with electrolyte, to have an immobilised electrolyte. These batteries were designed without the conventional vent plugs, which had vent holes for venting out hydrogen & oxygen gas. The recombinant technology developed and widely used had batteries with safety valves, which opened when the pressure inside the battery exceeded safety limits. These Sealed Maintenance Free (SMF) batteries are popular, and the batteries with such construction are also called Valve Regulated Lead Acid (VRLA) batteries. However, such maintenance free batteries could not be designed for all the applications due to certain constraints. In the meanwhile, certain other applications emerged that needed batteries. These needed portable maintenance free batteries with limited voltage & capacities. They were Digital Cameras, Medical Equipments, Mobile Phones, Toys, Drones, Hand Tools and Defense Instruments etc. etc. Thus, you can

observe that the usage of batteries has impacted mankind to such a large extent that it is now next to impossible to imagine life without batteries and energy storage. The portable applications could not use Lead Acid Batteries, which were heavy, needed a long time for a recharge, and contained corrosive electrolyte in the form of sulphuric acid. The development of Lithium Ion batteries as an alternative to Lead Acid Batteries emerged successfully for this segment. The Lead Acid Battery has been the most popular, widely used, robust, safe and economical choice for decades. It still continues as the preferred mode of storage of energy. The Lithium Ion battery manufacturers are trying to develop batteries for all applications, which presently use Lead Acid Batteries. Will the Lead Acid Battery be able to meet this challenge? Can Lithium Ion Batteries dethrone Lead Acid Batteries from its lofty pedestal? I have made an effort to list out the pros & cons of both the technologies and look forward to your comments on this matter. Times are changing fast. Climate change is just one of the indicators of things to come. Our environment is getting severely affected. Nature is showing its fury. It is now necessary for us to respond fast. We have to listen to the voice of reason. We have to respect nature and live in harmony, preserving nature for the sake of future generations. Lead Acid Batteries or Lithium Ion or Sodium Ion or Aluminum Air or Nickel Hydrogen? Do we have a choice?

TABLE OF CONTENT 1. Batteries – concepts explained 2. Introduction to batteries 3. Machines for battery manufacture 4. Terminology you may want to know 5. UPS & Home inverter systems 6. Inverter batteries 7. UPS reliability 8. Inverter & Battery selection 9. Cost of power generation using batteries 10. Replacement of batteries 11. Quality of battery water 12. Batteries in solar power applications 13. Cells in series & Cells in parallel 14. Battery chargers 15. Capacity rating of batteries 16. Electric vehicles & Batteries 17. Good…better…best lead acid battery

BATTERIES – CONCEPTS EXPLAINED

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efore we proceed ahead, I feel it is necessary to understand certain concepts.

Electricity, as such, cannot be seen. Its effects are visible and can be measured using various instruments. To convey the certain phenomenon of electricity, w.r.t., lead acid batteries, it has been my experience that a comparison with the behaviour of water, makes this subject, more logical and easier to understand. Coulomb – Electrical Unit Of Quantity The electrical unit of quantity is the Coulomb. It is the quantity of electricity transported in one second, by a current of one ampere. Thus, the Coulomb represents a definite amount of electricity and is like a gallon, which represents a definite amount of water. Current When water moves through a pipe, we have a flow or current of water. Similarly, when we have electricity flowing through a conducting element, we have a current flow of electricity. Resistance The pipe, through which water is passed, offers some resistance to the flow of water through it. The smaller the pipe diameter, the greater is the resistance. Also, the longer the pipe – the greater is the resistance to the flow of water through the pipe. Similarly, if an electrical conducting copper wire is used, the resistance to the flow of current is higher if a small cross section of wire is used or a long wire is used. Additionally, in the case of electricity, the material of the conductor is another parameter to be considered when we talk of electrical resistance. Usually, aluminium & copper are used as the conducting materials for cables.

Copper is considered the best conductor & is superior to aluminium. Voltage For water to flow in a pipe, pressure is necessary. Hydraulic pressure depends upon the head of water & is expressed as feet of water. Similarly, the electrical pressure required to cause a flow or current of electricity through a conducting wire is called voltage. The nominal voltage of a lead acid battery cell is 2.0 Volts. Irrespective of the size of the cell, the voltage is the same. This is due to the chemistry of the electrodes used in the manufacture of lead acid batteries, which exhibit a potential difference when charged. Two battery cells of different sizes may be compared with two water tanks, of different sizes, capable of storing different volumes of water but of the same height.

Depending on the level of water in the tank, the water pressure at the outlet shall change if the valves of both the tanks are kept open in a similar manner. When it comes to comparing this with a battery, if the current drawn from two batteries of different sizes (different capacities) are the same, then the voltage (pressure) shall reduce as the level decreases. It is obvious that the bigger capacity battery shall last for a longer time. A Comparison

Water Tanks Battery Cells Valve opening in the water tank is the same for both tanks – irrespective of the size of the water tank A load of 40W bulb

Thus, it is clear, from the comparison above, that the pressure in both water tanks being the same, due to the same height of water in both the tanks, with both the water outlet valves being uniformly open – the bigger tank has a larger capacity. It can dispense water for a longer period. Similar to the case of water – explained above – the larger capacity cell shall have a greater capacity to give out electricity than a smaller capacity battery cell. Series Connection To increase the pressure of water, we can add tanks one above the other so that the height of the water is more, and there is more pressure at the outlet valve.

In the case of battery cells connected similarly, in series, the voltage shall become additive. The voltage drop shall be gradual for a fixed load, in the case of a higher voltage battery, when compared to the drop in voltage of the lower voltage battery.

Parallel Connection: To increase the ability of water tanks to dispense water for a longer period of time, without the need for higher pressure, we can keep tanks side by side, instead of one above the other. In this case, the pressure shall be the same as for a single 'tank'.

In the case of battery cells connected in parallel – similar to the water tanks – the voltage shall remain constant at 2 Volts which is the voltage of one cell. However, the load can draw current for a longer duration since the capacity has increased. The capacity of the battery shall be the sum of the capacities of the number of cells connected in parallel.

Ohm’s Law Ohm's law states that the voltage between two points is directly proportional to the current or electricity passing through the resistance & directly proportional to the resistance of the conducting circuit. The formula is expressed as V = IR Thus, it expresses the relation between Voltage (V), Current (I) and Resistance (R). If there are two circuits connected to the same voltage, i.e. say we have a similar cell connected to the load, the current drawn by the load can be greater in that circuit of lower resistance.

As you can see in the illustration above – the tanks are of the same size, with the level of water in the tanks being equal. Hence the pressure at the outlet is equal. However, the discharge of water from one tank is through a small pipe, i.e. high resistance. In the other tank, the discharge is through a larger diameter pipe, i.e. low resistance to the flow of water. Obviously, the current of water flow shall be more from the tank, which has a larger diameter pipe, where the resistance to the flow of water is low.

In this sketch of batteries, we have two cells of the same voltage. One cell is connected to a high resistance circuit and the ammeter shows a low current flowing through it. The other cell connected to a circuit of low resistance shows a higher current passing through the circuit.

Now see the sketch below: -

The pressure from one tank is more in comparison to the pressure from the other tank. Since the resistance is the same, the flow shall be more from the tank having higher pressure. In the case of batteries, we observe that the heater load being the same; more power shall be delivered by batteries of higher voltage compared to a battery of lower voltage.

Please see the following sketch for a better understanding of the concept being explained:

RESISTANCE IS SAME FOR BOTH THE CIRCUITS From the above, it is obvious that the current is directly proportional to the voltage and inversely proportional to the resistance. The formula can be expressed as follows: V (Volts) I (Amperes) = -----------R (Ohms) Electrical Power The electric power is defined as the product of V, the potential difference and I, the electric current. i.e. P = VI Suppose we have 3 cells connected in series operating a lamp having a resistance of 6 ohms then the current drawn is 6 (Volts) I (Ampere) = ------------ = 1 ampere 6 (Ohms) Suppose we have 1 cell operating a lamp having a resistance of 2 ohms then the current drawn is

2 (Volts) I (Ampere) = ------------ = 1 ampere 2 (Ohms) Obviously, the lamp connected to a 6 Volts battery draws 6 Watts Power since P = 6 Volts x 1 Ampere = 6 W. By the same logic, the lamp connected to a 2 Volts battery draws 2 Watts Power since P = 2 volts x 1 Ampere = 2 W. The lamp of 6 Watts is more powerful and gives more light and is brighter than the lamp of 2 Watts which is less luminescent. Electrical power increases as voltage increases and as current increases. It is proportional to their product. The unit of electrical power is Watt. As an example, One Watt is equal to One Ampere flowing under the pressure of One Volt. Watts (W) = Volts (V) x Amperes (I) Back Up Duration It is apparent that when water is drawn from a tank by opening the outlet valve, the level drops as water flows out. The pressure reduces as the level comes down and becomes zero when the tank becomes empty. If the tanks are of the same size and have valves that can be opened partially or fully, we can operate the valves according to our needs .

On a similar basis, if we have two cells of the same size, as regards voltage & capacity, we can draw a lower current from one cell compared to the other.

The cell delivering lower current shall surely last longer, though both the cells are of the same voltage & capacity. Extending the logic further, it is obvious that an intermittent draw of current rather than a continuous draw of current extends service life since the energy is available for a longer duration. In fact, the intermittent rest period in such cases aids the battery and increases the available energy substantially in the case of lead batteries.

Cut Off Voltage

In the above figure, we have shown two tanks having water drain pipes at different levels. Since the drain pipe is fixed at a lower level in one tank, the water available for use in this tank is more than the water available for use in the other tank, where the drain pipe is fixed at a higher level. This is despite the fact that both the tanks are of the same size, with the top level of the water being the same, such that the pressure is the same. The varying level of drain pipes ensures that the flow of water is restricted, such that water will not flow out of the tank once it has dropped to a particular level. This cut off point decided by the placement of the drain is the cut off pressure point. Irrespective of the rate of flow of water, which can be adjusted by keeping the valve fully open, or partially open, or equally open, in both the tanks, the cut off of water supply shall be maintained, based on set level, depending on the location of the outlet in the tank. A low cut off ensures good output, i.e., output for a longer duration provided other parameters are constant for both the tanks. A higher cut off means less output. In the case of a battery, a similar working can be obtained by setting the cut off voltage. The cut-off voltage is the low voltage set point up to which a load can draw current from the battery during the discharge operation. It is therefore preferred to set a battery voltage cut off to as low a level as permitted by the battery manufacturer whenever one is designing a circuit, for best performance, as regards back up from a battery.

INTRODUCTION TO BATTERIES

A battery is a device which stores power. This power is used to run different

loads. The chemicals in the device, transform themselves, as they deliver the power to the load. Basically, speaking there are two types of batteries – Primary & Secondary. Primary batteries are those batteries, wherein a certain defined quantity of chemicals, are available. Once this quantity is spent, over a period of time, as electrical energy to power a device – the battery has to be discarded. Secondary batteries are those batteries, which can be used repeatedly, for a defined period. These batteries can be connected to a load and discharged, and then charged again for further discharge. The number of such cycles, of charge and discharge, is determined by the manufacturer. This cycle life is based on the output power, that the battery has to deliver and the defining factor is the amount of materials that the device contains. Battery life is defined as the number of cycles, or, number of years, depending on its application. Examples of secondary batteries commonly used, are the batteries, used in motorcycles, cars, buses, trucks, UPS systems, home inverters, street lighting, railway signaling, telecom applications, battery operated scrubbers, golf carts, material handling applications etc. etc. To summarize – a secondary battery can be defined as an electrochemical device, which converts chemical energy to electrical energy, by a reversible reaction. There are various types of secondary batteries viz. nickel cadmium, lead acid, nickel metal hydride, lithium ion, etc. etc. We shall try and concentrate on the topic of lead acid batteries, with references to other battery types restricted, to comparison only, as and when required. Lead acid batteries have been around for a very long time and are considered

a proven technology, which is rugged and safe to use. The battery as developed, in the initial stages has fundamentally remained the same, but developments over the years have culminated into the emergence of batteries with tubular plates, for industrial applications, which need a long life. Subsequent developments have resulted in Valve Regulated Batteries popularly known as Sealed Maintenance Free Batteries. The manufacture of lead acid batteries is, highly process oriented, requiring a basic knowledge of metallurgy, chemical engineering and mechanical engineering as well as electrical engineering. The entire process from raw material stage to final inspection, after the assembly of battery, needs 2 to 3 weeks conventionally. The following flow charts outline the process of an automotive battery and an inverter battery manufacture. You would have noticed that the process of manufacture of an "Inverter Battery", which has tubular positive plates, is a little different from the process of manufacturing of an "Automotive Battery". The battery designer adapts the product and ensures that the battery is made to suit the application.

To elaborate further – the automotive battery has to be compact, lightweight and be suitable for cranking applications. An industrial stationary battery has to have a long life and give power to the load over a defined duration, on a consistent basis, without delivering surge high current like in a engine starting application. Such stationary batteries need not be compact and can be heavy. Their being of low maintenance characteristics or no maintenance type, can however be an advantage. An industrial traction battery has to be as compact as possible, and shall need to be rugged enough to work as a prime mover of the electric vehicle, with a capability to undergo, at least one charge / discharge cycles every day. The variety of cells, which are required to be made in different sizes, to meet the varying demands of material handling vehicle manufacturers, is another matter altogether, in the case of industrial traction batteries. Attached are pictures showing the various types of lead acid batteries. The design characteristics are related to the application. The applications of various lead acid batteries and the target market details are also given.

MACHINES FOR BATTERY MANUFACTURE

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t is clear from the process flow chart of batteries that lead and oxide of lead are the main raw materials required for the manufacture of batteries.

The other components, which can be purchased from various vendors, viz., battery separators, tubular bags, plastic containers & covers, vent plugs etc., are easily available. The chemicals to be used in the process of paste mix manufacture, as well as sulphuric acid, can also be sourced from reputed vendors. These components and speciality chemicals are usually not made by the battery manufacturer. The process being quite cumbersome, the manufacture involves different sections/departments, carrying out varied activities over quite a long duration. Hence, a lot of machines are required, as mentioned in the process flow chart. As with any industry, it is possible to do a lot of automation and thereby reduce labour, increase productivity as well as production, optimise costs, improve quality, have consistency in the product etc. etc. However, the degree of automation is dictated by the individual manufacturer's market demands and one's capacity to invest in high value raw materials. The battery industry also has some manufacturers who do certain operations, manually or in a semi-automatic manner. This enables the setup of battery production as a SSI unit.

The photographs of various machines required for the production of battery plates, assembly and charging, are as shown.

Pressure Die Casting Machine DEVAKI - India

Negative Grid Casting Machine DEVAKI - India

Paste Mixer UNIK - India

Universal Pasting Machine UNIK - India

Double Side Pasting Machine DEVAKI - India

Tubular Plate Filling Machine UNIK – India

Curing Chamber UNIK - India

Plate Formation Rectifiers ADOR DIGATRON - India

Plate Dry Charging Chamber UNIK - India

Plate Brushing Machine UNIK - India

Plate Parting Machine UNIK - India

Lug Brushing Machine UNIK - India

Container Hole Punching Machine TEJASWI - India

Inter Cell Welding Machine TEJASWI - India

Heat Sealing Machine TEJASWI - India

Battery Charger ELIND - India

The machines mentioned cover the major processes. The jigs, fixtures, online test equipments etc., required for fitting on machines shall depend on the type of batteries to be manufactured. Other related equipments to be installed, which shall include demineralised water plant, test equipments, compressors, material handling equipments, effluent treatment plant etc. etc. shall depend on the proposed plant capacity. The list provides data to the extent possible. The detail of machine manufacturers covers only some machine manufacturers in India who are amongst the many other reputed manufacturers and who supply proven machines and is not an exhaustive list. Large scale manufacturers of batteries install lead smelting plants to recycle scrap batteries and manufacture Lead Alloy. They also produce Pure Lead from this alloying facility to process it further as Lead Oxide. Pure Lead is converted to Lead Oxide by processing it in Ball Mills or Barton Pots. India has a lot of vendors of equipments who make good quality machines to produce Lead Alloys & Lead Oxide.

TERMINOLOGY YOU MAY

WANT TO KNOW

UPS & HOME INVERTER SYSTEMS

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ninterruptible Power Supply Systems are very commonly referred to as UPS. Such a system used in homes, as standby power source, is often referred to, as inverter or home inverter. UPS systems are critical in certain applications i.e. in hospitals, clinics, jewelry shops, software industries, continuous process industries, telecom systems, electrical power stations, nuclear power establishments, airports, organizations using computers etc. etc. The three basic types of UPS topology are Off Line UPS, ON Line UPS and Line Interactive UPS. OFF Line UPS The most popular and widely used UPS systems, especially in homes and shops, are Off Line UPS. They are lighter and more affordable and also portable, due to being smaller in size, compared to other UPS systems. The Off Line UPS comes into play only in cases of power outage. The utility power supply connected to the system, is the priority power source, and the inverter is always on a standby mode. The inverter supplies power to the load only in case of power failure. The changeover switch in the Off Line UPS gets activated, to enable the inverter to draw DC power from the batteries and convert it into AC power for supply to the load. During such times, when the changeover takes place, by switching on power to the load from the inverter instead of mains utility – the critical load normally has a momentary power loss for a few milliseconds. However, equipments having SMPS (Switch Mode Power Supply) tolerate such a momentary power break, without getting adversely affected. As and when the power resumption takes place, the changeover switch ensures that the load gets the supply from the mains utility. The battery which has been partially or fully discharged, during the power

outage, now needs to be recharged. The charger which is a part of the UPS system now draws power from the main utility and charges the battery. Once the battery has been fully charged, the charge current reduces from boost to a trickle current, which is a low current, sufficient to compensate for the self-discharge losses of the battery. This trickle current, is such, that the battery is maintained, within a specified range of voltage, known as the float voltage. The advantages of the Off Line UPS are: r

Its portability, due to small size

r Affordable r

pricing

Efficient working, as there is no double conversion when utility power is being utilized.

The disadvantages of the Off Line UPS are: r Its

capacity limitation – usually available up to 3 KVA

r

It does not provide power conditioning & protection to the load, when the load is powered by the utility.

r

Has a momentary power break, during transition, from the utility power to AC supply, through inverter, when battery DC power is being used.

r It

is usually available, with a square wave inverter output.

On-Line UPS The On-Line UPS is a Double Conversion UPS. In an On-Line UPS, the incoming power from the utility supply, is converted to DC. The DC power maintains the charge condition of the battery, and is a source of supply to the inverter. The inverter then inverts the D.C. to A.C. supply, for the critical load. At times when the power supply from the utility fails the D.C. power is

drawn from the battery to ensure uninterrupted power supply to the load. As and when the power resumption takes place, the charger ensures that the battery is recharged sufficiently, to be ready for supply of power, in case of a subsequent power breakdown from the utility. The advantages of the On-Line UPS are: r

Supply of good quality power to the load. The critical load is guaranteed of power, which is free of spikes, voltage fluctuation, surges and frequency related issues.

r Absence

of transitional switching, in the cases of, power outages and power resumption.

r

Availability of UPS systems, of high capacities. Systems of 800 KVA are also available in a single unit configuration – thereby ensuring that continuous process industries or large hospitals can have reliable and clean power of good quality.

r

Reliability of operation and availability of uninterrupted power, without a break for even milliseconds, as and when, the battery takes over the load.

The disadvantages of the On-Line UPS are: r

Its bulky size and heavy weight. Such a UPS system needs a full size rectifier, which is capable of, supplying the total power connected to it, as well as, to charge the battery.

r Its

cost, which is naturally more, compared to other UPS designs.

r

Its efficiency, considering that this UPS uses the Double Conversion methodology.

r

Its requirement, of a bypass mechanism, to provide additional current, or to give power to the critical loads, at times of momentary demand. This becomes necessary, as and when, the UPS inverter is unable to supply

current, for in-rush demand. LineInteractive UPS The Line Interactive UPS functions in a manner similar to Off Line UPS. The UPS in this case, supplies utility power directly to the load as and when the power is available. However, the power is made to go through 1 or 2 stages of filters, with the aim of trying to filter off, some unwanted noise. A Line Interactive UPS also has a voltage booster, to regulate the output voltage. This makes the UPS more suitable, for operation in areas having input under voltage problems. Usually, these UPS operate in a wider range of input voltage, in the range of, – 30% and +10% of the nominal voltage. Instead of having a separate charger, to charge the batteries, and an inverter to convert DC from the batteries to A.C., for powering the load, the Line Interactive UPS usually has only one converter module, which performs the function of battery charging as well as discharging. The transition period is better when compared to OFF Line UPS; however, it is pertinent to note that, the transfer time exists. The advantages of the Line Interactive UPS are: r

It is small and compact – hence light weight also.

r It

is economically priced.

r It

is usually a sine wave inverter output type.

r

It has a comparatively faster switching time, as compared to an Off Line UPS.

The disadvantages of the Line Interactive UPS are: r

Its lack of output power quality control features comparable to On Line UPS.

r

Its unsuitability for critical power loads which are sensitive to transition

time. r Its

susceptibility to input frequency.

The above systems, all depend on battery power, as an alternative source of energy, and the selection of the battery, in terms of its capacity, charger compatibility and quality of the battery are all very important aspects, to be considered, while deciding on the UPS system purchase. As a precautionary measure, it is better to have a by-pass switch, to ensure availability of power, in case of failure of UPS or a fault in the UPS, especially in cases, where On Line UPS is being used. This by pass switch ensures that the loads are supplied power, in case of utility power availability, even if the UPS is not working.

INVERTER BATTERIES

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atteries of the lead acid kind popularly used in home inverter batteries are of two kinds – sealed maintenance free type or the flooded electrolyte type. The major difference at the customer’s end i.e. at the point of use, is that, the flooded electrolyte type battery can be maintained by water topping up, whereas the sealed maintenance free batteries cannot be maintained. Before we proceed further – let us first understand the working of an inverter coupled to the battery. A lead acid battery has a series of positive plates and a series of negative plates, inside. These are the electrodes. They are the reason, why power is delivered from the battery, through the inverter, to the load. The inverter converts DC power to AC power, in case of a power outage. During this period, the active material of the positive plates converts to PbSO4, from their active state of PbO2. At the same time the active material of the negative plates which is in the form of sponge lead, converts itself to PbSO4. Once this chemical transformation has taken place completely, the ability of the electrodes to deliver power is over. The battery needs to be recharged, by connecting it to a charger. The inverter unit consists of a suitable charger, which starts working, as soon as AC power is available. The charger unit draws A.C. power from the electric mains, and converts it to DC power, and gives it to the battery. A chemical transformation of PbSO4 to PbO2 in the case of positive plates, and sponge Pb in the case of negative plates, now takes place.

The discharged plates are now charged, for delivery of power to the load, in case of the next outage of power. This cycle of charge / discharge, with the accompanying chemical transformation continues, depending on product and maintenance quality of course, within the manufacturer’s design specifications. The chemical reaction explained above is depicted as follows: Material Particulars Positive Negative Electrolyte

Charged Discharged PbO2 PbSO4 PbSO4 Pb Dil. H2SO4 Very Dil. H2SO4

We shall now address the various questions, which a battery inverter user usually has, one by one. Why do inverter batteries bulge? The major cause of bulging of batteries is due to undercharge. The lead sulphate formed on both the positive & negative plates, during discharge, occupies more space, than the original materials of the plates, viz. lead dioxide & sponge lead. If a battery is left in a undercharged state, due to a fault in the inverter, or due to the charger being of smaller capacity w.r.t. battery requirement, or battery being of a large capacity, the battery plates shall not get sufficiently charged. The solution to this problem is to ensure that the battery coupled to an inverter, is of correct capacity, as per the recommendation of the inverter manufacturer. An overcapacity battery coupled to a under capacity charger, can end up with undercharged batteries, which, seemingly bulge and leave the customer dissatisfied, as regards power back up duration. The person buying the inverter must never suggest to the dealer, to supply a

higher capacity battery, for longer duration of power back up, without understanding the ability of the charger, to charge the battery from its fully discharged state. Why do inverter batteries need top up water? This query is relevant to flooded electrolyte batteries, which can be maintained by the user. The electrolyte in a lead acid battery is dilute sulphuric acid, which has the water component drying OFF, due to high ambient, or in certain cases, due to overcharge of the batteries. This water component needs to be replenished periodically. At times, when a customer negotiates too much on the price, the dealer ends up supplying a lower capacity battery, or an automotive battery instead of a tubular battery, to ensure that his margins are safeguarded. The voltage of the battery, he ensures to be, as per inverter requirements. Such a compromise, on the part of system dealer, ends up with overcharge of the battery. An inverter having a charger of say 15 Amps capacity to charge a 12V 120Ah battery, ends up charging a 12V 60Ah or 12V 80Ah battery, at a current of 15 Amps, which is very high for the 60 Ah or 80Ah battery, This shall surely heat up the lower capacity smaller battery, necessitating more frequent water topping up. A fault in the charger of the inverter, with the charger not tapering down the current, as the battery picks up charge, or not cutting off charging, as soon as the battery is fully charged, can be another possible reason for batteries needing more top up water, or needing top up water frequently. Why does the back up of an inverter battery reduce? The back up of an inverter battery depends on the load connected and the capacity of the battery.

More the load – lesser will be the backup duration. Lower the battery capacity – lesser will be the backup duration. Ensure that the load on the system is not increased over a period of time, to draw a false conclusion that the backup was better earlier, and, has reduced over a period of time. A natural reduction in backup over a long period of usage, despite load remaining constant, is acceptable as the battery ages. However do check tightness of battery cable connections and ensure that petroleum jelly is applied to the terminals periodically, during routine maintenance, so that loose contact is not the cause of this reduced back up duration. Why does water or acid bubble out of the top of inverter batteries? The most commonly observed cause of water coming out of the top of inverter batteries is overfilling of water during top up. Another possible reason is overcharging due to use of smaller capacity battery, or, a bigger capacity charger, or, a fault in the charger. Why do inverter batteries – sometimes explode? Batteries on charge release hydrogen gas, which needs to escape through the vent holes of the vent plugs, in the case of flooded electrolyte batteries. If the vent holes are covered due to dust or any material kept on top of the battery, the buildup of gases inside the battery increases the pressure on the battery container, leading to an explosion. Another possible reason for explosion is a metallic contact, which causes shorting of the positive and negative terminals of the battery. It is necessary to ensure that only insulated spanners or tools are used whilst working on batteries. Accidental shorting of terminals, or any metallic item coming in

contact with exposed terminals of the battery, can cause an explosion. Loose contact in the terminals, which can cause a spark, is to be avoided. When a battery is on charge – explosive hydrogen gases evolved, can come out through the vent holes. A spark due to loose contact can ignite and be the cause of a fire or explosion. These are of course rare occurrences and are not very common with low voltage systems of home inverter. To summarize the above 1) Avoid overfilling. 2) Ensure proper charging – no under charging 3) Keep terminals clean and tightly connected. 4) Periodically check whether the batteries are being overcharged and correct such a fault, if any. 5) Ensure that the load connected, to the batteries, is as per recommendation. 6) Clean the vent plugs during routine maintenance, to ensure that the vent holes are not clogged. Finally but most importantly – do buy inverter and batteries from a dealer who gives you the system, as per the manufacturer’s recommendations. Please note that an inverter meant for sealed maintenance batteries, has the charger settings, which are different from the settings, meant for flooded electrolyte batteries. Do not interchange a sealed maintenance free battery with a flooded electrolyte battery or vice versa, when you need to change the batteries of an inverter. This can be done only after changing the charger settings in the inverter.

UPS RELIABILITY

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eliability of a UPS system or Home Inverter system is a matter of concern to the user, more so if the UPS is meant to supply power in cases of emergency to highly critical and sensitive loads. To ensure the reliability of power availability, at times of power outage from the utility, maintenance of the UPS system, which includes batteries, is an absolute must. The maintenance must not be restricted to breakdown maintenance. The maintenance, in fact, must be preventive & predictive in nature. The schedule for preventive maintenance must be followed strictly, with a special focus on batteries, considering that batteries are the component needing a top up with water, corrosion resistant coating at contact points of the terminals, cleaning of the battery top as well as vent holes of the vent plugs etc. etc. The UPS per se, though it is complex electronic equipment, has no moving parts other than cooling fans if the fans are provided. Ensuring cleanliness of the UPS, using a cloth for wiping and a blower to blow off accumulated dust, is usually sufficient. The preventive maintenance of UPS and batteries must be assigned to qualified personnel, with greater stress, on battery maintenance. In any case, the UPS cannot be generally repaired, reset, or attended to, at the site, in case of problems in the UPS. It has to be usually done by the factory, or by factory trained personnel, in a service workshop. As long as a UPS manufacturer has the spares available in the city of operation and has an authorised service centre, the user has an assurance as regards UPS. Diagnosis of battery related issues and the promptness with which battery problems can be sorted out, as and when there are back up related issues, or a failure of UPS, is, therefore, the only matter of concern for the UPS user. The UPS vendor must have,

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An accessible and responsive service organisation.

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Battery service experts who shall attend to calls promptly.

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Technical ability and expertise to handle service needs of UPS and battery.

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A team offering periodic preventive maintenance, on a regular basis, in a defined manner.

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A scheme offering Annual Maintenance Contracts.

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A trained team, with quick response capability.

Distributors and dealers of UPS systems, who do not have the capability to solve problems at the site, are unsuitable for this work. Such vendors are unable to meet the needs of the customer, who invest in high end costly UPS systems. The customer, who is the end user, must be wary of such agencies and buy a UPS system or Home Inverter system based on the above guidelines.

INVERTER & BATTERY SELECTION

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t is possible to determine the inverter as well as battery capacity in Ah, which is required, for a certain load capacity, if the backup duration is already defined. The following steps and the constant termed as K factor selected from the chart shall enable the battery user to finalise the required battery capacity. Step 1 List out the loads to be connected to the inverter and arrive at total VA. In case W is known, the VA can be calculated for a presumed power factor of 0.86. Sr. No. 1 2 3 4 5 6 7 8

Appliances Ceiling Fans Tube Light CFL Lights Washing Machine Sandwich Toaster Microwave Oven Laptop Printer

2 2 5

Watts of each unit 75 40 20

Total Watts 150 80 100

Total VA 174 93 116

1

1000

1000

1162

1

750

750

872

1 1 1

1200 100 250

Qty.

1200 1395 100 116 250 290 Total 3630 4218 The total load in VA is 4218. Usually, the user switches off at least 50% of the load in case of power failure. Hence the inverter of 2109 VA is considered sufficient. However, in such cases, care must be taken to ensure that the maximum load of any one of the connected equipments does not exceed this 50% presumed load of 2019 VA. In the above case, the microwave oven needs 1395 VA, which is less than the 2109 VA calculated. Step 2

Find out from the inverter vendor as to what is the voltage of the battery to be connected to the inverter. Based on home inverters popular in India, we have the following data: Model Inverter Capacity Battery Voltage A 650 VA 12 Volts B 750 VA 12 Volts C 1050 VA 12 Volts D 1650 VA 24 Volts E 2000 VA 24 Volts F 2500 VA 36 Volts G 2500 VA 48 Volts H 3500 VA 48 Volts Step 3 Since the requirement based on the load in the above case comes to 2109 VA, we shall consider the 2500 VA inverter as suitable for our use. Step 4 Now we can determine the current that shall be drawn by the load ideally. We have the option of using inverter models F and G. Model F 2500 VA divided by 36 Volts = Draws 69.44 Amps DC Model G 2500 VA divided by 48 Volts = Draws 52.08 Amps DC Step 5 Find out the efficiency of the inverter. Usually, it is 80% or 85%. If efficiency is 80%, it means the efficiency is 80 divided by 100 = 0.80. If efficiency is 85%, it means the efficiency is 85 divided by 100 = 0.85. Step 6 Now we can determine the current that shall be required to be considered, for our operational needs, based on the inverter model, for the two different

efficiencies. Model F (36 Volts) 69.44 / 0.80 = 86.3 Amps. for 80% inverter efficiency. Model F (36 Volts) 69.44 / 0.85 = 81.6 Amps. for 85% inverter efficiency. Model G (48 Volts) 52.08 / 0.80 = 85.1 Amps. for 80% inverter efficiency. Model G (48 Volts) 52.08 / 0.85 = 81.2 Amps. for 85% inverter efficiency.

Step 7 Refer to the K factor chart, which lists out the factor to be used in the calculation, for different back up durations.

For e.g. Inverter model F is of 36 Volts & shall need 3 batteries of 12 Volts in series. Inverter model G is of 48 Volts & shall need 4 batteries of 12 Volts in series. If we choose to use a Model F inverter with 85% inverter efficiency and need a backup for 2 hours, the chart of K factor above specifies a factor of 3.16. Multiply 81.6 Amps required by the inverter of 85% efficiency with 3.16 to arrive at 81.6 x 3.16 = 257.85 Ah say 250 Ah CONCLUSION Inverter Model F Inverter Efficiency 85% Backup Duration 2 Hours Inverter Capacity 2500 VA Battery Voltage 36 Volts Battery Ah 250 Ah

COST OF POWER GENERATION USING BATTERIES

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ith the increasing trend of working from home (WFH), and with the installation of inverters at home no longer considered a luxury, almost all residences have opted for a fairly large capacity home inverter, in addition to a small UPS for computers. Shops and clinics in urban areas have been equipped with an Uninterrupted Power Supply system for many years. Of late, this trend of installing UPS is being observed in rural areas, where power interruptions are relatively more frequent. Many professionals have shifted back to their hometowns during the lockdown and are continuing to work from home. Schools & colleges are also conducting classes online. The demand for UPS systems has therefore gone up drastically. One question, which is often asked, is whether the power bills from the utility power go up, as and when a UPS is installed. In other words, does the consumption of power from the utility increase? On the other hand, there are a few people who seem to have a contrarian view. They ask as to whether it is better to utilise battery power through the newly installed inverter on a daily basis and avoid using utility power for 2 to 3 hours, though the power from the grid is available. They want to do it, at least over the weekend, when WFH is not being done. We shall now see an approximate calculation of the cost of power generation in cases where a battery is connected to the UPS system.

Part II – Units Of Power Generated A battery of 120Ah @C10 is to be considered as a battery of 86 Ah @C3. It can deliver 28.68 Amps for 3 hours i.e. 12 Volts x 28.68 Amps x 3 hours = 1032.48 Wh 1032.48 Wh translates to 1.03 units per day. If the battery is being used for 12 days x 12 months x 3 years, i.e. 432 cycles - it means the battery can deliver 432 cycles x 1.03 units = 444.96 units….. 445 units of power. Summation Based on the above, we observe that the cost of 1 unit of power works out to Rs. 26.71 i.e. total cost Rs.11887.00 divided by 445 units. Conclusion The cost of power generated using a battery is very high, and hence the usage

of inverter/UPS power must be optimised. Suggestions & Recommendations 1) Ensure that battery is maintained well, so that it works, for more than 3 years. 2) Ensure that you do not compromise on the battery quality with price as the only criteria at the time of purchase, since battery cost comprises of the main cost of the system. The better the life of a good battery - lower shall be the cost of generated power. 3) In case of any fault in the UPS or Inverter, indicating that the battery is being overcharged or over discharged or undercharged, please arrange for prompt service so that the battery is not damaged. 4) Check inverter and get the same cleaned/serviced periodically and surely at the time of fitment of the replacement batteries. 5) In case of an inordinate increase in electricity bill, check whether the battery is getting overcharged, or whether there is a malfunctioning of inverter, with a possibility of continuous charging at boost rate. Notes 1) The cost of the battery and the cost of the inverter are not considered for the cost of power calculation. It is also presumed that the inverter shall be good enough beyond the 3 year period when the battery is most probably due for replacement. The AC side losses due to inverter efficiency have not been considered. Inverter efficiency is presumed to be excellent. 2) If the cost of the battery is considered as Rs. 13500.00, and battery replacement is expected to be after 3 years, and if this cost is added to the power generation cost, the unit cost of power shall escalate to Rs. 57.00 per unit.

REPLACEMENT OF BATTERIES In case sealed maintenance batteries are to be replaced with flooded electrolyte batteries in a UPS system.

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hile a flooded electrolyte lead acid battery and sealed maintenance free battery are both lead acid batteries, the user of batteries, often times, matches the voltage as well as the battery Ah capacity, presuming that such a change over makes no difference to the working of the UPS system. Whilst it is true that the performance characteristics are quite similar, in both cases, one needs to understand that these batteries have a marked difference, w.r.t their charging parameters. This special and important difference, incorporated at the manufacturing stage, is the design feature, which makes both types of batteries unique in different ways. A flooded electrolyte battery made for large UPS systems is usually manufactured as a series of 2V cells to be connected in series. The electrodes are lead plates, classified as positive plates and negative plates. The positives are tubular positive plates, i.e., spine lead grids surrounded by lead oxide active materials, encased by acid resistant cloth tubular structure, to prevent active materials from shedding. The negatives are flat plates, i.e., a cast lead grid structure, on which lead oxide paste is applied and subsequently dried in a controlled atmosphere to prevent shedding. The active materials of negative have expanders, retaining fibers and carbon as special additives, added to the lead oxide during the paste mixing stage. As far as sealed maintenance free batteries are concerned, both the positive & negative plates are usually made as flat plates. The chemicals added to a positive paste mix are, however different, from the many chemicals added to a negative paste mix. Nowadays, a few manufacturers are reintroducing gel filled batteries with tubular positive plates & pasted negative plates into the market. Another major difference pertains to the quantity of electrolyte used in the batteries or cells.

The electrolyte used in both types of lead acid batteries is dilute sulphuric acid. A flooded electrolyte battery has abundant electrolyte and hence the sp. gravity of the electrolyte used for these batteries are generally lower than the sp. gravity of electrolyte used in a sealed maintenance free battery. The lower specific gravity means lesser corrosion, especially at elevated temperatures. The abundant volume of electrolyte, also acting as a coolant, makes the flooded electrolyte battery more suitable for working in areas of high ambient without the need of air-conditioned rooms for the batteries. One of the reasons for the enhanced life of these batteries, in comparison to sealed maintenance free batteries, is the availability of electrolyte, far in excess of the quantity required, purely for the reaction. On the other hand, sealed maintenance free batteries have a restricted volume of electrolyte. This electrolyte is sulphuric acid, which has been mixed with certain chemicals to make it like a gel so that it does not flow out. An alternative technique used is to trap the electrolyte in the pores of the separator. The separator in such cases is an insulating porous material used between the positive & negative plates to prevent physical shorting. The material of the separator is a glass mat, and, in industry parlance, it is called Absorptive Glass Mat or AGM separator. The specific gravity of the sulphuric acid electrolyte is usually higher than its flooded electrolyte counterpart and this ensures that the limited volume has a high enough specific gravity reading at the end of discharge to ensure conductivity, which is necessary for recharge acceptance. Is it possible to replace Sealed Maintenance Free (SMF) batteries with Flooded Electrolyte Low Maintenance batteries in a UPS system?

All stationary batteries are connected to a charger, which gives a trickle current, to maintain the batteries within a specified range of float voltage, as and when the batteries are not supplying power to the load. This trickle current ensures that all self-discharge losses are compensated for, thereby guaranteeing that the battery is in a state of readiness to deliver the power,which it is expected to deliver, as and when needed in case of an emergency. This is common for AGM type as well as flooded electrolyte batteries. However, what varies in the charger used for AGM batteries and the conventional type flooded electrolyte batteries is very important as well as critical, from the battery life point of view. The change is in the float voltage setting of the charger for both these types of batteries. There is another significant change that pertains to boost voltage or top of charge voltage. All AGM batteries need a float voltage setting of the charger to be in the range of 2.20 to 2.25 volts per cell. The maximum voltage setting of the charger meant for AGM batteries is limited to a voltage below the gassing voltage. All flooded electrolyte batteries need a float voltage setting of the charger to be in the range of 2.16 to 2.20 volts per cell. The maximum voltage setting of the charger meant for flooded electrolyte batteries is set to be in a broad range of 2.55 volts to 2.75 volts per cell. This is known as boost charge voltage. Hence, it is absolutely necessary to change the charger setting, as and when the type of battery connected to the load and the charger is changed, from AGM type to flooded electrolyte type. The charger setting has to suit the battery. Hence a UPS system, meant for AGM batteries, cannot be used for Flooded

Electrolyte batteries & vice versa without changes in charger setting. Another aspect to be considered before changing AGM batteries to Flooded Electrolyte batteries is the room floor size, as well as ventilation. In case the physical limitations of size, or the environmental demands of safety, do not allow such a replacement of AGM batteries with flooded electrolyte batteries, then adjusting the charger to suit batteries does not serve your purpose. Flooded electrolyte batteries cannot be used, where acid fumes that are generated during boost charge and vented out through vent holes are not permitted. Flooded electrolyte batteries are to be kept upright to avoid acid electrolyte spillage, unlike the AGM batteries, which can be kept in any orientation. Flooded electrolyte batteries of capacity equivalent to AGM batteries are bulkier compared to AGM batteries and occupy more space. The battery user who has experienced better battery life with tubular plate batteries, of the conventional flooded design, compared to battery life and reliability of SMF battery, must understand the various aspects explained above.

QUALITY OF BATTERY WATER

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he water used for topping up must be clear, without any suspended impurities, colourless & odourless. It is recommended by battery manufacturers that only demineralised or distilled water is used for topping up as and when the electrolyte level drops. The pH of water used must be between 6 and 7. In case the water to be used for topping up needs to be stored, such storage shall be in a glass or plastic container. Impurities, if any, shall not exceed the limits specified below: -

Considering that test facilities may not be available easily for testing of water, the purchase of water for topping up batteries, used in homes for UPS systems, may be done from reputed automobile service stations, spare parts dealers, or fuel stations. Please do not use bottled drinking water or tap water. The effects of different impurities on battery life and performance are as follows:

BATTERIES IN SOLAR POWER APPLICATIONS

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atteries, as and when used in solar applications, are connected to an array of photovoltaic modules through an inverter. The inverter has a charger and charge controller, which ensures that the battery is charged using energy from the Sun in the daytime. The charged batteries get discharged and deliver power to the load as and when required. The various A.C. equipments like fans, television sets, lights etc., are powered through the inverter, which converts, D.C. to A.C. Such solar powered systems, which store power in batteries, are very popular in remote areas, where electric power, generated by conventional methods, is not available. With the increasing cost of power, shortages in power supply, interruption of power and breakdown of supply due to excessive demand, putting a strain on the power generating companies etc. etc., solar photovoltaic systems are gaining wider acceptability, even in areas where electric power is easily available. Another reason for the rising popularity of solar power usage is environmental consciousness amongst the general public at large and various subsidies offered by the governments. The promotion of renewable energy sector by the various heads of state all over the world helped in the growth of industries in this segment.

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However, the widely used and, nowadays, popular roof top solar installations and buildings integrated solar panels do not need battery backup for storage of energy. Now let us understand the lead acid batteries used for the storage of power, as and when these are used for solar photovoltaic applications. A lead acid battery, irrespective of the application, is the same in so far as the basic chemical reactions are concerned. However, variations that have a

lasting effect on life and performance can be made in the processing stage, depending on the application for which the battery is to be used. Manufacturers use AGM separators or Gel Electrolyte to make the batteries, which are sold as sealed maintenance free batteries. Manufacturers use tubular positive plates to make batteries last longer in stationary or electric vehicle applications. Within the realm of stationary batteries are - UPS / Inverter batteries and batteries for Solar Photovoltaic applications. I am often asked as to what should be the difference in the construction of the batteries of these two applications. The first thing we need to understand is that both these batteries are used in a stationary mode. However, cycling is more frequent or regular in the case of batteries used for solar application. The depth of discharge in the case of batteries used for solar application is normally limited, though, compared to batteries used for inverters. Another factor to be considered is recharge. The batteries connected to a solar application shall receive a charge in an irregular manner and for a limited duration, unlike batteries used in UPS or Inverter application, wherein the charging is from a definite AC source and in a defined manner. The batteries used for solar applications may be installed in a remote location having limited or no easy accessibility. Hence maintenance may be irregular and erratic too, compounded with the non-availability of trained personnel in such areas. A battery meant for solar application is expected to last much longer than a battery meant for UPS/Inverter application. Hence a solar battery has to be more rugged in construction. Changes in design or process at the manufacturer's end ensure that the solar battery meets the required criteria

and is different from the UPS/Inverter batteries. To enable the solar battery to revive quickly, after a full discharge, in rainy days, where the battery has not got power from the Sun and the depth of discharge has been more, a higher electrolyte volume helps by ensuring that the electrolyte specific gravity is high enough to ensure better conductivity. This conductivity becomes critical when a deep discharged battery has to be revived using solar power. To guarantee good charge acceptance in a solar battery, a more than adequate cross section of lead in the pillars and bus bar of the plate groups helps by ensuring that there is no voltage drop during the charging cycle. This takes care of the limitation of charge current available for a short duration and received in an irregular manner. To take care of irregular maintenance, where the maintenance in flooded electrolyte stationary batteries is primarily water topping up, a provision for abundant electrolyte volume needs to be made in the design stage. The electrolyte above the top of the plates has to be much more than in an inverter battery. Cell containers that can accommodate large volumes of electrolyte are chosen for solar applications vis a vis for inverter applications. To have a battery for solar application last much more than a UPS /Inverter battery - the paste used for making the negative plates of the solar battery has to be of higher density. The tubular bags used for solar application have to be of overall good quality to ensure that the positive plates last really long. The web thickness of separators used for solar photovoltaic application has to be higher than the separators used for a normal battery. If the container is able to accommodate more number of plates per group, then it is preferable to make a battery with more number of plates than use lesser and taller plates to obtain the required capacity. This shall contribute to

better charge acceptance. Due care must be taken to ensure that there is no voltage drop, however, by ensuring that the taller pillar required in such cases is of the adequate cross section. The additional electrolyte in the solar battery ensures that the battery is well suited for very hot as well as very cold climatic conditions. Due to abundant electrolyte in the cells, the specific gravity is sufficiently high even when the battery is fully discharged and this prevents freezing of the electrolyte and the resultant problems associated with freezing. The abundant electrolyte contributes to keeping the battery cool in areas of high ambient. This becomes important since corrosion of battery plates in the acidic atmosphere is otherwise accelerated at high temperatures. The above additional points taken care of from the battery manufacturer's end - of course, in addition to the normal quality assurance parameters of paste formulation, curing and charging etc. - shall ensure that the lead acid stationary battery performs well in a solar photovoltaic application. In certain cases where tall plate lead acid cells are used - issues pertaining to Partial State of Charge (PSOC) or acid stratification may arise in spite of the battery being well designed. In such instances, one needs to look at the charger capacity or panel sizing.

CELLS IN SERIES & CELLS IN PARALLEL

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y now, you would have understood the concept of voltage and capacity.

The following examples with the numbers and sketches shall make the concept of series and parallel connection clearer. Whenever batteries are connected in series, the voltage is additive and capacity is constant.

The positive of one battery is connected to the negative of another battery and as per sketch. 3 batteries of 12V 100Ah connected in series shall deliver 36V 100Ah. 12V + 12V + 12V = 36 Volts The capacity of one battery is 100Ah and due to the series connection, capacity of 3 batteries shall be remaining the same 100Ah. Whenever batteries are connected in parallel, the capacity is additive and voltage is constant. The positive of one battery is connected to the positive of another

battery and the negative of one battery is connected to the negative of another battery as per sketch. 3 batteries of 12V 100Ah connected in parallel shall deliver 12V 300Ah. 100 Ah + 100Ah + 100Ah = 300 Ah The voltage of one battery is 12V and due to parallel connection, the voltage of 3 batteries shall remain the same 12 Volts. At times batteries are connected in a complex combination of series and parallel connection. This is uncommon but done especially in cases where high Ah capacities are required. For the sake of understanding the method of calculation, we shall see how such a connection is done using sets of 3 nos. of 12V 100Ah batteries.

In such cases, care must be taken to ensure that discharging and recharging is uniform in all strings of batteries. It is possible to check the D.C. current using a clamp meter. The current can be kept constant in parallel strings by keeping the length and cross section of the cables constant. This ensures that the resistance being the same, the current is uniformly distributed. Alternatively – the introduction of electronic controls in the circuit to monitor and vary the current of parallel strings is possible. However, this shall entail additional costs.

BATTERY CHARGERS

A charger is a device which returns the charge to a discharged battery. As such, a lead-acid battery needs to be charged after manufacture and later on during regular use. Charging done after assembly of the battery at the time of commissioning of battery for use is referred to as commissioning charge or initial charging. Subsequent charging after discharge is known as recharging. The devices used for initial charging at the manufacturer's factory or the distributor/dealer's premises are usually rectifiers or chargers which use utility AC power. These chargers are of constant current DC output type or, at times constant voltage chargers. The recharge of the battery is carried out by various methods – depending on the application. Automotive batteries, including the ones used for motorcycles, are charged using the vehicle's alternator. Home inverters & UPS batteries of the stationary type are charged using a float/boost charger which is a component inside the inverter. Batteries coupled to solar photovoltaic systems are charged by solar panels through a charge controller, which is also a part of the inverter. The charge controller limits the input charge to the battery as the battery gets charged. The solar panels draw energy from the Sun in this case. Batteries used in E-Rickshaws or electric vehicles or scrubbers, sweepers & golf carts are referred to as Deep Cycle Batteries and these batteries are charged after every cycle of use. Since such batteries are fully discharged, they need to be recharged using onboard chargers or external chargers having output DC current, which reduces as the battery voltage increases. Traction batteries, i.e. batteries used in industries for motive power applications, are charged using chargers having substantial output current at the start, which tapers down to an equalising charge current as the battery reaches a full state of charge.

In the charging process, AC power is converted to DC power and then supplied to the battery or a bank of batteries. This process oxidises the lead sulphate of the positives to lead dioxide and reduces the lead sulphate of the negatives to sponge lead by a simultaneous redox reaction. Simultaneously the density of the electrolyte increases. The electrolyte being sulphuric acid, a noticeable rise in specific gravity of the electrolyte is observed as and when a battery is charged. The specific gravity is measured using a hydrometer. We shall now discuss the various methods of charging batteries for a better understanding of the terms used in industry parlance. a) Constant Current Method. b) Constant Voltage Method. c) Modified Constant Voltage Method. d) Taper Charging. e) Trickle Charging. f) Float Charging. g) Equalising Charge. a) Constant Current Charging: Constant current charging is often used to charge all types of lead-acid batteries at the manufacturer's premises, where the Ah input is a critical factor that is monitored and recorded as a quality parameter. Constant current charging is also used invariably in the laboratory because of the convenience of calculating ampere-hour input and because constant current charging is required to determine Ah and Wh efficiency. Constant current charging at very low currents is often resorted to at site to decrease the sulfation in batteries which have been over-discharged and/or under charged. b) Constant Voltage Charging :

In this method of charging, the charging is done with the voltage maintained at a constant defined value per cell. The value of the initial or starting current of a completely discharged battery, when put on charge, often exceeds the normal and usually high rate of charging. During the charge, as the battery picks up a charge and the voltage of the battery slowly increases and reaches the gassing voltage, the current is set to automatically reduce to a value much below that of the high starting rate. In such chargers, the end of the charge currents are set very low and are always lower than the finishing rate current of the constant current chargers. c) Modified Constant Voltage Charging : Modified constant voltage charging is used for stationary batteries used in UPS applications, home inverters and telecom application batteries wherein the charger or rectifier is always connected to the battery. In this case, the charger has an upper current limit. The charge current is continuously fed till the battery reaches a defined voltage. After the battery has reached the defined voltage, the charger current starts reducing as the voltage rises and the battery gets fully charged. Once the battery is fully charged, the battery is maintained within a range of voltage known as float voltage so that it is ready for discharge in a fully charged state. The modified constant voltage charge, with constant and high starting currents and lower finishing current rates, is also used for traction and monobloc deep cycling batteries. These batteries are rated for discharge at the 5 hr. rate to a depth of 80%. The recharge current of these batteries is adjusted so that the charging is completed in a 6 to 8 hrs. duration for batteries used in temperate climate conditions. The recharge current of these batteries is adjusted so that the charging is completed in 12 to 14 hrs. period for batteries used in tropical climatic conditions. The charger is set for the constant potential in a range of 2.35 V to 2.40 V per cell, which is the gassing

voltage, and the starting current is settable in a range of 12 to 20 A per 100 Ah of the rated 5-h ampere-hour capacity. The initial current is maintained constant until the average cell voltage in the battery reaches 2.35 V to 2.40 V per cell. The current drops at constant voltage, tapering down to the finishing rate of 3 A to 5 A per 100 ah, which is then maintained for a period of 3 to 6 hrs. using a settable timer. The time of charge is selected such that Ah input which goes into the battery, is around 10 % to 20% more than the amperehour output of the previous discharge. The charging time can be increased or reduced by setting the initial current limit rate in such chargers. d) Taper Charging: Taper charging is similar to the modified constant voltage charging method. However, in this case, the charger has fewer controls and thereby costs less. Hence there is a possibility of more gassing during the recharge along with an increase in cell temperature. The degree of the gassing and temperature rise shall depend on the current taper profile and is thus a characteristic of the charger design. Battery life can be affected in such chargers due to the increase in battery temperature and gassing if the chargers are not selected appropriately. The end of the charge is often related to a fixed voltage rather than a fixed current. Modified constant voltage charging methods with initial currents based on battery Ah capacity is to be selected based on ambient temperatures at the place of use to have a good battery performance and life. e) Trickle Charging: A trickle charge is a continuous constant current charge at a low rate. The charge current is usually 1% of the battery Ah capacity. The trickle charges current is used to maintain the battery in a fully charged condition. A trickle charger delivers a current significant enough to compensate for self-discharge

losses as well as to restore the energy to a battery discharged during intermittent use of the battery. This method is usually resorted to for SLI batteries when the battery is removed from the vehicle in a service station or when the battery is idle for long periods duly disconnected from its regular charging source. It is also used for Genset batteries. In the case of Genset, the trickle charger is permanently connected to the battery so that the battery remains fully charged always and can respond to emergency situations. f) Float Charging : Float charging is a low-rate charge current which is fed to a battery. This sort of charging is done to maintain the battery in a state of readiness for discharge as and when demanded by the load. A float charger keeps the battery in a fully charged condition. This method of charging is used mainly for stationary batteries. The float voltage for a flooded electrolyte vented battery is usually 2.16 V to 2.20 V per cell. The float voltage for a lead-acid VRLA/SMF battery is usually2.20 V to 2.25 V per cell. The float charger ensures that the voltage of the battery is continuously maintained within the defined parameters of the set voltage range. g) Equalising Charge : It is commonly believed that whilst a battery is being `float charged’, it will have consistent voltages and specific gravities and shall be in a fully charged condition. This shall necessarily not be the case always, especially in batteries having tall plates. A phenomenon known as acid stratification can take place, leading to an uneven current distribution between the plates of the cell. Stratification is the separation of electrolytes into distinct layers of differing densities. The density of the electrolyte at the bottom of the cell shall be higher than the density of the electrolyte at the top of the cell. The resultant uneven current distribution and the varying `acid strength’ can

cause variation in cell plate characteristics. There can be a gradual discharge of portions in the plates located in the low current density areas. Initially, the overall cell voltage remains at the correct float level and no variations are seen when the cell is new. This partial discharge in some areas of the cell plates causes sulphation. The degradation of cell quality due to sulphation worsens with time. The battery's internal resistance gets affected, causing considerable variations in individual cell voltages as well as specific gravity. The only corrective action possible to rectify any such battery or cell is an equalising charge. Such a battery should be periodically equalised by charging with a constant current which is 4 to 6 percent of the ampere-hour capacity at the 10 hour rate in the case of stationary batteries. Batteries must be fully recharged prior to equalising. The recharge prior to equalising charge should continue until such time as the specific gravity and voltage readings of individual cells have reached a maximum value and have ceased to rise for a period of three consecutive hourly readings. In the case of traction batteries also, equalising is required. Traction batteries are not connected to a charger when in use and are not on float charge. Traction batteries are fully discharged to 80% depth of discharge almost on a daily basis. These batteries need an equalising charge periodically. Battery manufacturers usually recommend the equalising charge current rate as 3 to 5 percent of the ampere-hour capacity at the 5 hour rate. Traction batteries are also to be equalised after a full recharge. The purpose of equalising is attaining the constancy of voltages and specific gravities. The actual value of voltage is not an important factor at this point in time. It is recommended that equalising charges be carried out as per the manufacturer's advice..

CAPACITY RATING OF BATTERIES

T

his test is done to determine the capacity of the battery, to deliver the current in amperes which a battery has to deliver, for the defined period, as per its rating, in line with manufacturer's specification. This capacity is usually mentioned on the battery. The manufacturer usually specifies the battery in conformance with industry standards, providing the following details: 1) Battery voltage in volts. 2) Battery capacity in ampere hours. 3) Battery rating as C10 or 10 hr. 4) Battery serial number. 5) Month and year of manufacture. 6) Make or brand name of the battery. Let us take the case of a tubular inverter battery used in homes. Suppose we have a 12 V 100 Ah battery rated at 10 hr. rate; the battery is expected to deliver 10 amperes constant current for 10 hrs. to an end voltage of 10.5 Volts. The battery behaves differently at various rates of discharge, i.e. it lasts longer at lower currents of discharge and lasts for a lesser period at higher currents of discharge. As per the standards IS 13369:1992, the latest amendment in the year 2003, the accepted performance of a battery for various rates of discharge is as follows:

Rate Of Discharge C10 C5 C3 C1

Capacity expected End Voltage as %age of C10 Capacity 100 % 1.80 Volts 83.3 % 1.80 Volts 71.7 % 1.80 Volts 50.0 % 1.75 Volts

What this means is that, in the case of a 12V 100 Ah battery, we can expect performance in line with I.S. standards as below:Capacity Rating C10

No. Of Hours 10 hrs.

To End Voltage Per Cell 1.80 V

Discharge Current 10 Amps

-& not 20 C5 5 hrs. 1.80 V 16.66 Amps. Amps. & not 33 C3 3 hrs. 1.80 V 23.90 Amps. Amps. & not 100 C1 1 hr. 1.75 V 50.00 Amps. Amps. Using the above logic, it is clear that a 12 V 100 Ah battery can be classified as a 12V 120 Ah battery by the battery manufacturer since the same battery lasts longer when discharged at lower currents. 12V 100Ah C10 rated battery delivers 10 A for 10 hours (12V 100Ah @C10) 12V 100Ah C10 rated battery delivers 06 A for 20 hours (12V 120Ah @C20) The battery is the same. It has been rated differently. Thus, it is clear that discharge rate w.r.t. time is not a linear relationship.

ELECTRIC VEHICLES & BATTERIES

E

lectric vehicles are the latest trend, with a reported 8.5 lakh plus vehicles on Indian roads, as on December 2021.

The major vehicles are of course two wheelers and three wheelers, which are being used to ferry passengers. Cargo carrying three wheelers and Passenger E-cars together account for the balance 8% of the approx. total volume. Concerns about air pollution and climate change are forcing the adoption of electric vehicles as the cleaner and environment-friendly means of transportation. In India, the central government has introduced the Faster Adoption and Manufacturing of Electrical Vehicle Scheme, popularly known by the acronym FAME. The government has also reduced GST on electric vehicles, as well as charging infrastructure, to promote the development of charging stations. The Government of India has also approved a Production Linked Incentive scheme to encourage the setting up of manufacturing facilities for advanced Chemistry Cells in India. Similar PLI schemes have been announced for Automobiles and Auto Components for electric vehicles. With the increase in the cost of petrol and diesel, many fleet management companies are considering the option of converting to electric vehicles, especially for the last mile delivery requirements. The running cost of electric two wheelers is substantially lower, approx. one fourth to one fifth of the cost. This is in comparison to the cost of running a two wheeler on petrol. The acceptance of electric vehicles as the future, from an economic standpoint, as well as the requirement to save the environment, is now a given. The general population and the various heads of state all over the world are in consensus on this matter.

The adoption of this technology, however, imposes certain challenges in terms of charging infrastructure, high prices of the vehicles, availability of good batteries at economical prices, safety related issues pertaining to batteries - which at times crop up in the case of lithium ion batteries, recycling and disposal of scrap batteries, standardisation of charging sockets, educating and training of the users, development of battery management systems which are easy to use, and, of course, mileage. Fortunately, all these challenges are being addressed effectively and in a fast manner due to a time frame being imposed for an all-electric vehicle scenario. The battery industry is also gearing up to meet the various challenges head on in a successful manner. As of now, Lithium Ion batteries are popular & mostly used in electric vehicles. These batteries are very costly and constitute 40% to 50% of the cost of electric vehicles. With the increase in demand for electric vehicles, the requirement for batteries is set to skyrocket. In fact, another application, which also uses Lithium Ion batteries, is the renewable energy segment. Lithium Ion batteries are widely used in consumer electronics, but EV batteries are bigger batteries and hence more complex. As and when bigger batteries or systems of higher voltages and higher currents are required, the quality of Lithium Ion batteries becomes more critical. In fact, Battery Management Systems have an important role to play when Lithium Ion batteries are used in Electric Vehicles. The reason for this is that Lithium Ion batteries are prone to thermal runaway problems, leading to an explosion of batteries and resulting in fire. These may be due to either or a combination of reasons viz. electrical, thermal, mechanical abuse or internal short circuit. Storage of Lithium Ion batteries is again a challenge. The following care

needs to be taken: 1) Lithium Ion batteries need to be stored in a well-ventilated area. 2) Adequate provision needs to be made for firefighting in case of a fire. 3) Personnel must be trained for the careful handling of batteries. 4) Monitoring of stores, using CCTV cameras, is a must. 5) Sensitive sensors to detect smoke & fire, complete with alarms, have to be installed. 6) Adequate fire insurance, with all safeguards in place, has to be ensured. 7) Employing trained personnel to handle fire & emergency situations is also important. It is advisable to store Lithium Ion batteries in a segregated area and away from other inflammable materials. As far as fire extinguishers are concerned, experience has shown that Halon and CO2 are effective, though there is a limited understanding in this matter as of now. In case of fire due to Lithium Ion batteries, sand has been effectively used to cover the battery to allow a controlled burn out. Water, when added, has been found to make the fire worse. As regards Lithium Ion batteries, there are mainly four types 1) Lithium Iron Phosphate 2) Lithium Nickel Manganese Cobalt (LiNMC) 3) Lithium Nickel Cobalt Aluminum Oxide (NCA) 4) Lithium Cobalt Oxide (LCO) The Lithium Iron Phosphate and Lithium Nickel Manganese Cobalt are popular for use in Electric Vehicles. Lithium Cobalt Oxide (LCO) batteries are used mainly in portable electric products like mobile phones, cameras, laptops and toys. Lithium Nickel Cobalt Aluminum Oxide (NCA) are used in

medical devices like ventilators, dialysis systems, anaesthesia machines and limited industrial applications. Though Lithium Ion is popular and presently used for electric vehicles, there is a lot of R & D going on simultaneously to explore better technologies. This is, all the more so, especially due to the non-availability of Lithium in sufficiently large quantities in India, a feeling of discomfort due to incidents of some vehicles catching fire, lack of clarity as regards recyclability and disposal. There are a few startups segregating used lithium batteries and working on these cells to give it a second life. The second life, of course, shall be with a reduced capacity, for sale, accordingly. Below is a chart comparing the lead acid battery to two variants of Lithium Ion batteries from an academic point of view.

The question on the mind of many people, including the minds of manufacturers of lead acid batteries, is whether it is the end of the road for Lead Acid Batteries and whether Lithium Ion shall replace Lead Acid Batteries in various applications. Well, I do not think it is possible to totally displace Lead Acid Batteries for the following reasons: 1) Safety The major cause of concern for all battery users is safety. Lead Acid Batteries have a proven track record and are very safe to use. Lithium Ion Batteries are relatively unsafe, with cases of the explosion of batteries and incidents of fire being more frequent, in the case of Lithium Ion Batteries. Fires due to Lithium Ion Batteries, generate toxic gases. Moreover, putting off these fires is difficult too. 2) Availability of Lithium & Cobalt Lithium mines exist in Argentina, Bolivia and Chile, with some quantities in U.S.A., Australia & China. Cobalt required for making Lithium Ion Batteries is mainly found in Congo. Importing Lithium & Cobalt or Lithium Ion Cells for assembly from abroad is akin to importing petroleum products for petrol & diesel vehicles from oil rich nations. Lead on the other hand, being recyclable, is easily available.

3) Recyclability & Disposal Though the claims of a longer life compared to Lead Acid Batteries may imply that Lithium Ion Batteries shall need to be replaced after a lot of use, and thereby less frequently, it is still frightening to imagine the colossal waste that shall be generated in the future, if an effective mechanism to recycle & dispose of the scrap batteries is not devised, by then. Moreover, such recyclers must be available with efficient and environmentally safe technologies, all over the world, in various locations so that recycling is feasible and practical. 4) Cost The cost of Lithium metal is high and further increasing, thereby making it prohibitively costly for certain applications. The difference in cost w.r.t Lead Acid Batteries is such that, a lot of users shall prefer Lead Acid Batteries if given a choice, despite the shorter life and cumbersome maintenance requirements that Lead Acid Batteries entail. Some applications, like large size material handling equipments and high capacity die loaders, may accept Lead Acid Batteries. 5) Reparability Due to the ease of repair of lead acid battery, familiarity of the product and the rebate available on scrap battery – the acceptance of the technology of Lead Acid Batteries continues, despite the purported advantages of Lithium Ion Batteries, in terms of quick recharge, remote assistance and longer life characteristics. 6) Retrofit Options A lot of vehicles with internal combustion engines and a lot of electric vehicles, as well as material handling equipments with lead acid batteries, are not going to be scrapped, at least for 10 years from now, or, say 10

years from the date of sale. Hence lead acid batteries shall need to be made for these customers, who shall not opt for any retrofit on their vehicles, to replace Lead Acid Batteries with Lithium Ion Batteries since such a retrofit, is likely to be very costly & cumbersome. 7) Power Demand Situation The growth of the renewable energy sector has put a lot of focus on Solar Energy and there is an ongoing effort to reduce the use of thermal and nuclear power plants. This means that the requirement of storage of power shall increase. Solar energy, which can be directly used through roof top panels, is limited to day time use. If the energy harnessed from the Sun has to be used at night, we need to store the power. For this, one needs batteries. Lead Acid Batteries are proven, robust, safe and inexpensive compared to Lithium Ion. As long as the design of the Lead Acid Batteries meant for solar applications are done properly – maintenance is also not an issue. It has been observed that Lead Acid Batteries are designed adequately well, last for over 10 to 12 years in solar photovoltaic applications. There are many more similar reasons. Considering the few reasons stated above, we can surmise that the Lead Acid Battery industry shall survive the advance of Lithium Ion Battery or any other similar types of batteries, into its domain. The growth of the renewable energy segment, which is inevitable due to the need for the preservation of the environment, shall become a dominant reason for the demand for batteries. Lead Acid Batteries shall therefore survive but needs technology upgradation. The areas of improvement in Lead Acid Batteries on which the future generation can probably work are 1) Development of software adapted to the battery industry needs. This shall

reduce inventory, which is a major area of investment of borrowed funds, with scope for reduction of battery cost. Reduction in interest cost on working capital is necessary. 2) Another area with scope for reduction of battery cost is in electric power consumption. We observe high power consumption in battery industries, in the department of charging of batteries. Development of software that shows the efficiency of charger, and recommends usage in terms of optimisation, and gives alerts in case of inefficient usage, shall benefit the battery industry. 3) Development of an App with real time data of buyers and sellers. This App shall be useful, especially for new manufacturers of components as well as entrepreneurs setting up a new battery manufacturing industry. This shall also promote exports by giving wider exposure to manufacturers based in India. 4) Improving the efficiency of batteries by developing additives, which give exponential benefits in terms of life & capacity. 5) Cost reduction in manufacturing by simple & economic automation of plant and machinery. 6) Development of a digital probe to measure the specific gravity of electrolyte at an economic cost is another necessity. 7) Development of Battery Management System suitable for Lead Acid Batteries, tailored for Electric Vehicle Applications & Stationary Battery Installations. 8) Development of battery chargers with much higher efficiencies than the presently available chargers. 9) Development of a method to refine & reuse the dilute sulphuric acid coming out from various processes.

10) Development of an effective and low cost effluent and acid fume treatment plant for small scale industries. 11) Development of an acid recirculating charging system suitable for small scale industries.

GOOD… BETTER… BEST LEAD ACID BATTERY

A good

lead acid battery is one that sufficiently meets customer expectations by being suitable for that specific application in all respects. Hence an automotive battery is expected to be as light as possible but powerful enough to crank the automotive engine for a defined number of times, repeatedly at times, for an expected life period of 2 to 4 years. A stationary monobloc battery with tubular positive plates designed for home inverters is expected to be as compact as possible, with a life expectancy of 3 to 5 years. A stationary 2 Volt cell with tubular positive plates, designed for use, coupled to UPS systems in large industries, power stations or telecom systems etc., is expected to work for long durations at times of power outages. These batteries are expected to last for 10 to 12 years and actually last for 15 to 18 years and even more at times. A stationary 2 Volt cell with tubular positive plates, designed for use, coupled to a solar photovoltaic system and installed in a remote location is expected to work with minimal or no maintenance for a period of 10 to 15 years, depending on ambient conditions and depth of discharge. These batteries are usually charged by solar photovoltaic cells and designed for quick charge acceptance as well as use for up to 5 days of continuous discharge without a recharge. Monobloc stationary tubular plate batteries used in solar applications are expected to deliver a minimum of 5 years of useful life. A motorcycle battery, made using ultra-thin battery plates, is made such that it delivers power to meet the demanding needs of today's hi-tech two wheelers. The batteries used in two wheelers nowadays are expected to even crank the engine since quite a few two wheelers are designed with push button self-start technology. The power delivered by motorcycle batteries,

which literally fit in the palm of a hand, is to be experienced to be believed. A motive power battery, known in industry parlance as a traction battery, is used to power material handling vehicles, which are used in airports, large industries, railway stations, docks etc. etc. These batteries being the prime movers, are discharged on a daily basis and recharged for use on the following day. These batteries at times act as a counterweight and are very heavy. They are made rugged since they are cycled on a daily basis usually. Batteries meant for scrubbers, sweepers, electric vehicles, boom lifts, cranes and recreation vehicles are also deep cycling batteries and these are designed to be rugged but light weight. The different types of lead acid batteries used with specific requirements for varying applications have to be designed r

with differing sp. gr. of operations

r with

varying pitch of assembly

r with

separators of differing thicknesses

r

with abundant or limited electrolyte volume, depending on battery size limitations

r

with alloy of lead having calcium or antimony or selenium etc., depending on expected performance characteristics

r with

paste density variation

r with

fine tuning of certain processes etc. etc. etc.

Thus, you see that lead acid batteries used for different applications have minor changes in processes, or materials used, or in design characteristics. Once a good battery has been designed and the product has been validated in the field, after a proper review of the design, it is necessary to freeze the design, material specifications and process to have a consistent product.

The consistency of the product, which has been accepted by the user as an acceptable and good product, as well as the after sales technical and service support, is what helps a manufacturer build his brand value for a bigger market. The customer ultimately decides, based on user experience, as to which is the BEST battery in the market.