battery is a device that stores energy and then discharges it by converting chemical energy into electricity. Typical batteries most often produce electricity by chemical means through the use of one or more electrochemical cells

Battery is a device that stores energy and then discharges it by converting chemical energy into electricity. Typical batteries most often produce electricity by chemical means through the use of one or more electrochemical cells

1. CONTENTS Introduction Standards Section 1- General Terminology Battery (Principle of Operation) Construction of battery Components of a battery Types of batteries Selection of DC Voltage levels Load Classification for Sizing Batteries (TCE and IEEE 1115) Battery Replacement (Common for both Lead-Acid and Ni-Cad batteries )

2. Introduction This guide provides general information on batteries, selection of batteries, sizing calculation for battery and battery charger with typical examples and also stating norms to be followed for battery areas. Electrical energy can hardly be stored. In general, the storage of electrical energy requires its conversion into another form of energy. In batteries the energy of chemical compounds acts as storage medium, and during discharge, a chemical process occurs that generates energy which can be drawn from the battery in form of an electric current at a certain voltage. For a number of battery systems this process can be reversed and the battery recharged, i.e. the intake of electric energy can restore the chemical composition that contains higher energy and can closely reestablish the original structures within the battery. As a consequence, two different battery systems exist Primary batteries that are designed to convert their chemical energy into electrical energy only once. Secondary batteries that are reversible energy converters and designed for repeated discharges and charges. They are genuine electrochemical storage systems.

3. The current drawn from a battery is DC and listed below are the application of the DC current in an industrial plant. The DC power is required to run any DC motors if present. (For example starting DC battery for Diesel generator ) At the time of power supply failure, the battery is required to supply D.C. power requirements of essential circuits for safe shut down of the station, vital instrumentation, controls, communication system, DC annunciation and emergency lighting . The duration for which each type of D.C. load will have to be supplied by battery when the normal power supply fails is different. The same may be continuous or for short time duration or momentary This guide provides the recommendation for sizing the voltage level, AH capacity, number of battery requirement in addition to the recommendation for the installation of DC system.

4. This guide is categorized as listed below . Section 1 General Basics of batteries, various terminologies and voltage Levels Section 2 Lead Acid Battery Types, selection, installation, maintenance and sizing of lead acid battery Section 3 Nickel Cadmium Battery/Types , selection, installation, maintenance and sizing of nickel cadmium batteries . Section 4 Battery Charger Types , selection and modes of battery charger Section 5 Checklist Recommended Checklist for selection and installation .

5. The following standards are applicable for batteries and battery chargers. IEEE 450 Recommended Practice for maintenance, Testing, and Replacement of Vented Lead-Acid Batteries for Stationary Applications IEEE 484 Recommended Practice for Installation Design and Installation of Vented Lead- Acid Batteries for Stationary Applications IEEE 485 Recommended Practice for Sizing Lead-Acid Batteries for Stationary applications IEEE 946 IEEE Recommended Practice for the Design of DC Auxiliary Power Systems for Generating System IEEE 1115 Recommended Practice for Sizing Nickel-Cadmium Batteries for Stationary Applications IEEE 1144 Recommended Practice for Sizing Nickel-Cadmium Batteries for Photovoltaic ( PV)Systems IEEE 1184 Guide for the Selection and Sizing of Batteries for Uninterruptible Power system

6. IS 1651 Stationary Cells and Batteries, Lead-Acid Type (with Tubular Positive Plates) Specification IS 1652 Stationary Cells and Lead-Acid Type with Batteries, Plante Positive Plates –Specification IS 8320 General requirements and methods of test for lead acid storage battery IS 10918 Specification for vented type nickel cadmium batteries IEC 896 Stationary lead-acid batteries Tests on Battery as per IEEE 450 Acceptance Test - A constant-current or constant-power capacity test made on a new battery to confirm that it meets specifications or manufacturer‘s ratings . Performance Test - A constant-current or constant-power capacity test made on a battery after it has been in service, to detect any change in the capacity . Service Test - A test in the as found condition‖ of the battery‘s capability to satisfy the battery duty cycle.

7. Terminology Ageing Factor The battery reaches the end of its useful life when it fails to deliver 80% of its rated capacity. In order to deliver its rated capacity even at the end of the estimated life of the battery, a correction factor is taken as aging factor. Active material Constituents of a cell that participate in the electrochemical charge/discharge reaction. Ambient Temperature The temperature of the surrounding environment. Battery/ Battery Bank One or more cells electrically connected to form a unit. Commonly termed "battery" which applies for a single cell also. Boost Charge Boost charging involves a high current for short period of time to charge the battery. It is generally if the battery has been discharged heavily. Boost charge enables the quick charging of depleted batteries. Capacity Number of ampere-hours (Ah) a fully charged cell or battery can deliver under specified conditions of discharge. Capacity Test A discharge of a battery at a constant-current or constant-power to a specified terminal voltage. Cell Basic electrochemical unit used to store electrical energy. Critical Period That portion of the duty cycle that is the most severe, or the specified time period of the battery duty cycle that is most severe. Cut-off voltage Cell or battery voltage at which the discharge is terminated. The cutoff voltage is specified by the manufacturer and is a function of discharge rate and temperature.

8. Continuous load Continuous loads are energized throughout the duty cycle. These loads are those normally carried by the battery charger and those initiated at the inception of the duty cycle. Non-continuous Load Non-continuous loads are energized only during a portion of the duty cycle. These loads may switch on at any time within the duty cycle and may be on for a set length of time, be removed automatically or by operator action, or continue to the end of the duty cycle Duty Cycle The loads a battery is expected to supply for specified time periods while maintaining a minimum specified voltage. Electrolysis Chemical dissociation of water into hydrogen and oxygen gas caused by passage of an electrical current. Electrolyte Medium which provides the ion transport function between the positive and negative electrodes of a cell. Equalizing Charge Charge applied to a battery which is greater than the normal float charge and is used to completely restore the active materials in the cell, bringing the cell float voltage and the specific gravity of the individual cells back to ―equal‖ values. Float Charger Method of charging in which a secondary cell is continuously connected to a constant-voltage supply that maintains the cell in a fully charged condition. Float cum Boost charger A battery charger which performs both the functions of float as well as boost charging

9. Freshening charge sequence Freshening charge is applied to a battery after installation and before connection to the system to retrieve any lost charge during shipment. Gassing Evolution of gas from one or more electrodes resulting from electrolysis of water during charge or from self-discharge. Significant gassing occurs when the battery is nearing the fully charged state while recharging or when the battery is on equalizing charge. Performance Factor This factor is considered to estimate the performance of the battery at a discharge rate other than the nominal rate. The performance factor is defined as the ratio of the amperes that can be drawn from the battery for ‗t‘ minutes to the rated capacity (AH), for a particular end cell voltage. Pilot cell A reference cell (or) selected cell which is used to measure the specific gravity (or) represent the average state of parameters of the battery. Primary Battery or Primary Cell Cell or battery which is not intended to be recharged and is discarded when the cell or battery has delivered its useful capacity. Secondary Battery or Secondary Cell A battery or cell that after discharge may be restored to its charged state by passing an electrical current through the cell in the opposite direction. (Also called storage or rechargeable battery) Spare Capacity Factor A spare capacity factor shall be considered to take care of any future additional load. Specific Gravity Ratio of the weight of a solution to an equal volume of water at a specified temperature. Used as an indicator of the state of charge of a cell or battery. Sulfation Formation of lead sulfate crystals on the plates of a lead-acid battery.

10. Temperature Correction Factor This factor is considered to take care of the variations in performance of the battery at different temperatures. While high temperature results in higher performance, lower than nominal temperature (27°C) lead to lower performance due to sluggish chemical activities. The performance factor is divided by the temperature correction factor to obtain the corrected performance factor. Terminal Connection Connections made between cells or at the positive and negative terminals of the battery, which may include terminal plates, cables with lugs, and connectors. Trickle charge Method of charging in which a secondary cell is either continuously (or) intermittently connected to a constant current supply in order to maintain the cell in fully or nearly full charged condition. Vented Battery A battery in which the products of electrolysis and evaporation are allowed to escape freely to the atmosphere. These batteries are commonly referred to as flooded. Sealed Battery These types of batteries confine the electrolyte, but have a vent or valve to allow gases to escape if internal pressure exceeds a certain threshold. Alkaline Cell Cell containing alkaline electrolyte Solid Electrolyte Cell with an ionically conducting solid as electrolyte

11. Battery (Principle of Operation) A battery is a device that converts the chemical energy contained in its active materials into electrical energy by means of an electrochemical reaction. The basic electrochemical element of the battery is referred as the cell. A battery consists of two or more cells electrically connected in series to form a unit. A secondary battery is one which can be used, charged and reused. They are widely used for industrial purpose. A cell consists of a positive and negative electrode. The negative electrode supplies electrons to the external circuit (or load) during discharge. The positive electrode accepts electrons from the load during discharge. The electrolyte completes the internal circuit in the battery by supplying ions to the positive and negative electrodes. The separator is used to electrically isolate the positive and negative electrodes. If the electrodes come in contact, the cell will short-circuit and become useless. The separator allows the transfer of between the electrodes . A potential difference exists between the positive and negative electrodes that deliver electric current to the external circuit. The potential difference (usually measured in volts) is commonly referred to as the voltage of the cell or battery. The capacity of a cell/battery is the amount of charge available expressed in ampere-hours (Ah).

12. Example: A battery expressed as C10 200Ah,12 V means that the battery will discharge 20A of current per hour for 10 Hours. 12V is the potential difference that exists between the positive and negative terminal of the battery . • Batteries are often classified by the type of electrolyte used in their construction. • There are three common classifications: acid, mildly acid, and alkaline. • Acid-based batteries often use sulphuric acid as the major component of the electrolyte. • The electrolyte used in mildly acidic batteries is far less corrosive than typical acid-based batteries and usually includes a variety of salts that produce the desired acidity level. • Alkaline batteries typically use sodium hydroxide or potassium hydroxide as the main component of the electrolyte . • Alkaline batteries are often used in applications where long-lasting, high-energy output is needed Battery Connections Cells and batteries may be connected in series, parallel, or combinations of both. Cells or batteries connected in series have the positive terminal of one cell or battery connected to the negative terminal of another cell or battery. This has the effect of increasing the overall voltage but the overall capacity remains the same Cells or batteries connected in parallel have their like terminals connected together. The overall voltage remains the same but the capacity is increased. .

13. Batteries may also be connected in a series/parallel combination. Batteries are added in series until the desired voltage is obtained, and in parallel until the battery bank meets capacity requirements. Only like cells or batteries should be connected together Connecting cells or batteries of different rating or manufacturer may produce undesirable or even dangerous results. Construction of battery Based on their method of construction batteries are either called flooded (or vented) or sealed. Flooded and sealed batteries also differ in their operation. Flooded Batteries Flooded cells are those in which the electrodes/plates are immersed in electrolyte. Since gases created during charging are vented to the atmosphere, distilled water must be added occasionally to bring the electrolyte back to its required level. Sealed batteries These types of batteries confine the electrolyte inside the battery container, but have a vent or valve to allow gases to escape if internal pressure exceeds a certain threshold value .

14. Components of a sealed battery Valve Regulated Batteries The valve-regulated battery is the most common type of sealed battery. These types of sealed batteries have a spring-controlled valve that vents gases at a predetermined pressure. Typical pressure thresholds are from 2 to 5 psig, depending on the battery design. Although the term "valve- regulated" is often used synonymously to describe sealed batteries, not all sealed batteries are valve- regulated. Some battery designs employ replaceable vent plugs or other mechanisms to relieve excess pressure. Sealed batteries were developed to reduce the maintenance required for batteries in active service. Since electrolyte levels are preserved by trapping and recombining off-gasses, there should not be any need to add distilled water over the life of the battery. These batteries are often misnamed "maintenance free." In fact, all maintenance practices applicable to unsealed type batteries are applicable to sealed type batteries. The only exception is that electrolyte levels cannot, and should not need to be, maintained.

15. A typical vented battery used for backup power

16. Components of a battery Based on their method of construction batteries are either called flooded (or vented) or sealed. Flooded and sealed batteries also differ in their operation. Active Material The term ‗active material‘ means the components of the cell reaction. This term usually concerns materials in the positive and negative electrode, but may also include certain components of the electrolyte, like sulfuric acid in lead-acid batteries. The active material suffers chemical conversion on charge and discharge, and thereby often changes its volume. Non Active Material Non active materials are divided into conducting and non-conducting components Conducting components The current has to be collected from the active material and conducted to the terminals. Often the current conductor simultaneously acts as a support for the active material. When a number of electrodes are connected in parallel within the cell, corresponding connecting parts like pole bridges are required . Additives, like carbon or metal powder, sometimes are required to improve the conductivity within the active material, especially in thick layers Separators Separation of the two electrode reactions requires that any electronic contact between positive and negative electrodes has to be strictly prevented. Otherwise, a short circuit is formed that discharges the battery. On the other hand, the ionic current through the electrolyte should be hindered as little as possible

17. Terminal seals The seal of the terminals is a critical element. In vented batteries with liquid electrolyte it has to prevent creeping of the electrolyte, which especially is observed for batteries with alkaline electrolyte. With sealed batteries, the post seal, furthermore, has to prevent the escape of hydrogen, and also has to prevent the intake of oxygen from the surroundings. Special techniques have been developed for the different battery systems . Vents and Plugs Vent plugs are required with a number of battery systems because of secondary reactions that generate gases which must escape. Vents, as used for some rechargeable batteries, are simple openings that allow gas flow in both directions, i.e. out of the battery but also vice versa. The openings in such vent plugs are small to minimize water loss by diffusion of the water vapor. In modem batteries, such vents mostly are equipped with porous disks that prevent ignition sparks or flames from entering the cell and hinder the escape of electrolyte fumes from the cell. Valves allow only the escape of gas and are required in valve-regulated lead- acid batteries for the escape of hydrogen, but are also used in most other sealed batteries to prevent damage of the cell in the case of a too high internal pressure when the battery is abused, e.g. overcharged at a too high current rate or reversed. Rechargeable button cells in general have a rupture vent (breaking point) embossed into their metallic cell container that opens on a preset overpressure before the cell explodes. Safety features that prevent overpressure sometimes are also employed in primary batteries . Types of battery Based on the material of construction of the electrodes and electrolyte, there are different types of batteries. The most commonly used Batteries for industrial purpose are Lead Acid Battery Nickel Cadmium Battery .

18. . Voltage Level (V DC) Application 24 Instrumentation and control Process Control 30 Small Plants with small switch boards Isolated auxiliary plants 48 Instrumentation and control Process Control 110 Small plants with multiple load points Outdoor substation Process Plant Isolated auxiliary plants 220 Large plants with multiple load points Switchyards / Process Plant Table 1: The common ratings of DC voltages and their applications are listed below However DC voltage level shall be decided based on the type of the plant and project requirement .

19. Load Classification for Sizing Batteries (TCE and IEEE 1115) The following table lists the common applications of DC loads with classified duration. Duration Application Non-continuous loads Trip relay / Trip coil currents of circuit breakers. Switchgear operations (Closing Coil) Starting currents of all automatically started D.C. motors. Motor driven valve operations Emergency Pump Motor Critical ventilation system motors Fire protection systems Isolating switches Continuous loads Indication Lamps, indicators in panels Auxiliary Relay (DC Operated) Annunciator (Control Schemes) Emergency Lighting Communication system Continuously energized coils Converters Continuously operating motors

20. Battery Replacement (Common for both Lead-Acid and Ni-Cad batteries) The recommended practice is to replace the battery if its capacity reaches below 80% of the manufacturer‘s rating. After completion of a capacity test, the user should review the sizing criteria to determine if the remaining capacity is sufficient for the battery to perform its intended function. The timing of the replacement is a function of the sizing criteria utilized and the capacity margin, compared to the load requirements available. Whenever replacement is required, the recommended maximum time for replacement is one year. Failure to hold a charge, as shown by cell voltage and specific gravity measurements, is a good indicator for further investigation into the need for battery replacement. Prior to selecting the replacement battery, it is prudent to review the battery sizing calculation to ensure the calculation is still valid for the new battery‘s characteristics and any load changes. Battery Disposal All battery components, when discarded, contribute to the pollution of the environment. Some of the components are relatively organic and can quickly merge into the ecosystem without noticeable impact. Other components, such as steel, nickel, and plastics, while not actively toxic to the ecosystem, will add to the volume of a landfill, since they decompose slowly. However, the heavy-metal battery components, which, when discarded, can be toxic to plants, animals, and humans. Cadmium, lead, and mercury are the heavy-metal components most likely to be the target of environmental concerns.