Glossary of Terms



AGM (Absorbed Glass Mat): A type of non-woven separator material comprised almost entirely of glass microfibers that absorbs and retains the electrolyte leaving no free electrolyte in the cell to spill. VRLA batteries made with this material are often referred to as "AGM" batteries.

Acid: In the lead acid storage battery industry, "acid" implies "sulfuric acid", and is used to describe the electrolyte or liquid in the cell.

Active Materials: The materials in a battery which react chemically to produce electrical energy. In a lead-acid battery the active materials are lead peroxide (positive) and sponge lead (negative).

Activation: Process for making a dry charged cell functional by introducing electrolyte.

Air Oxidized: A charged negative plate that has been removed from the electrolyte and permitted to discharge in an air atmosphere with the evolution of heat. Plates so treated must be recharged before they are capable of producing any useful electrical energy.

Alloy: A combination of two or more metals, as a mixture, solution or compound. See also "ANTIMONIAL LEAD ALLOY", "CALCIUM LEAD ALLOY".

Ambient Temperature: The temperature of the surrounding cooling medium, such as gas or liquid, which comes into contact with the heated parts of the apparatus, usually refers to room or air temp.

Alternating Current: An electric, pulsating current, in which the direction of flow is rapidly changed, so that a terminal becomes in rapid succession positive then negative.

Ammeter: An ammeter is an instrument for measuring electrical current. See also "AMPERE-HOUR METER"." Ampacity,Current carrying capacity in amperes."

Ampere: The practical unit of electric current that is equivalent to the steady state current produced by one volt applied across a resistance of one ohm. It is one tenth of an abampere.

Ampere-Hour: A measure of the volume of electricity, being one ampere for one hour, or 3600 coulombs. It is used to express battery capacity, and is registered by an ampere hour meter, or is obtained by multiplying the current in amperes by the length of time that the current is maintained.

Ampere-Hour Capacity: The number of ampere-hours which can be delivered under specified conditions as to temperature, rate of discharge, and final voltage.

Ampere-Hour Efficiency: The electrochemical efficiency expressed as the ratio of the ampere-hours output to the ampere-hours input required for the recharge.

Ampere-Hour: Meter An instrument that registers the quantity of electricity i n ampere-hours.

Assembly: 1. The process of combining the various parts of cells and batteries into the finished product. 2. Any particular arrangement of cells, connectors, and terminals to form a battery suited for a desired application.


Battery (Storage): A storage battery is a connected group of two or more storage cells (common usage permits this term to be applied to a single cell used independently). Batteries are sometimes referred to as "Accumulators" since electric energy is accumulated by chemical reaction.

Bayonet Vent: A term originally applied to a design of quarter turn vent plug the lower portion of which resembles a bayonet, both in appearance and locking arrangement.

Boost Cells: Cells with higher capacity than the tests cells which are used to help maintain constant discharge current in a manual discharge test.

Boost Charge: A partial charge given to a storage battery usually at a high rate for a short period. It is employed in motive power service when the capacity of a battery is not sufficient for a full day's work.

Boot: Plastic piece used at foot of plate, especially a wrapped plate, for retention and insulation.

Bridge: The ribs or element s s upport ing structure, molded, or cut to fit into the bottom of a ribless jar or container in order to provide ediment space under the element thereby preventing short circuits.

Burning: The welding together of two or more lead parts such as plates, straps, connector; by means of heat and in some cases, additional metal supplied by a stick called a burning strip.

Burning Center: The center-to-center distance between adjacent plates of the same polarity.

Burning Stick: A lead stick of convenient size used as a supply of joining metal in lead burning.

Button: The finished "button shaped" area produced on the top surface of a connector or terminal by the post burning operation.


Cadmium (Cd): A metallic element highly resistant to corrosion, used as a protective plating on certain steel parts and fittings.

Cadmium Electrode: A third electrode for separate measurements of the electrode potential of positive and negative plate groups.

Calcium Lead Alloy: A lead base alloy that in certain applications can be used for battery parts in place of antimonial lead alloys Most common use is in stationary cells.


Capacity Test: A test wherein the battery is discharged at constant current at room temperature to a cutoff voltage of usually 1.70 volts/cell.

Carbon Burning Outfit: A metallic rod and insulated handle, mounting a pointed carbon rod; used for lead burning on service locations where the usual gas flame equipment is not available.

Carboy: A large cylindrical container or bottle of plastic or glass used to ship acid.

Cast: To form a molten substance into a definite shape by pouring or forcing the liquid material into a mold and allowing it to solidify (freeze).

Casting: A metallic item, such as one or more grids, straps or connectors; produced by pouring or forcing molten metal into a mold and allowing it to solidify.

Cell (Storage): A storage (secondary) cell is an electrolytic cell for the generation of electric energy in which the cell after being discharged may be restored to a charged condition by an electric current flowing in a direction opposite to the flow of current when the cell discharges.

Charged: The condition of a storage cell when at its maximum ability to deliver current. The positive plate contains a maximum of lead peroxide and a minimum of sulfate, while the negative plates contain a maximum of sponge lead and a minimum of sulfate, and the electrolyte will be at maximum specific gravity.

Charged and Dry: A battery assembled with dry, charged plates, and no electrolyte.

Charged and Wet: A fully charged battery containing electrolyte and ready to deliver current.

Charging: The process of converting electrical energy to stored chemical energy. In the lead-acid system, charging converts Lead Sulfate (PbSO4) in the plates to Lead Peroxide (PbO2) (positive) or Lead (Pb) (negative plate).

Charging Plug: The male half of a quick connector which contains both the positive and negative leads.

Charging Rate: The current expressed in amperes at which the battery is charged.

Charging Receptacle: The female half of a quick connector housing both positive and negative leads.

Circuit: A system of electrical components through which an electric current is intended to flow. The continuous path of an electric current.

Circuit (Series): A circuit that has only one path for the flowof current. Batteries arranged in series are connected with negative of the first to positive of the second, negative of the second to positive of the third, etc. If two 12-volt batteries of 50 ampere-hours capacity each are connected in series, the circuit voltage is equal to the sum of the two battery voltages, or 24 volts, and the ampere-hour capacity of the combination is 50 ampere-hours.

Circuit (Parallel): A circuit that provides more than one path for the flow of current. A parallel arrangement of batteries (usually of like voltages and capacities) has all positive terminals connected to a conductor and all negative terminals connected to another conductor. If two 12-volt batteries of 50 ampere-hour capacity each are connected in parallel, the circuit voltage is 12 volts, and the ampere-hour capacity of the combination is 100 ampere-hours.

Cold crank Rating: The cold crank rating refers to number of amperes a lead-acid battery at 0°F (-17.8°C) can deliver for30 seconds and while maintaining at least 7.2 volts (1.2 volts per cell). This is commonly referred to as CCA (Cold Cranking Amps).

Conductance: The ability to transmit current in a circuit or battery.

Corrosion: The chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties. The positive lead grids in a battery gradually corrode in service often leading to battery failure. Battery terminals are subject to corrosion if they arenot properly maintained.

Compound: An asphaltic, pitchlike material used as a cover-to-jar battery sealant.

Constant-Current Charge: A charge in which the current is maintained at a constant value. (For some types of lead-acid batteries this may involve two rates called a starting and a finishing rate.)

Constant Potential Charge: See "CONSTANT VOLTAGE CHARGE".

Constant Voltage Charge: A charge in which the voltage at the terminals of the battery is held at a constant value.

Container: Housing for one or more cells, commonly called a "JAR".

Cover: The lid or cover of an enclosed cell generally made of the same material as the jar or container and through which extend the posts and the vent plug.

Cover Inserts: Lead or lead alloy rings which are molded or sealed into the cell cover, and to which are burned the element posts thereby creating an effective acid-creep resistant seal.

Curing: Chemical conversion process which changes lead oxides and sulfuric acid to mixtures of tetrabasic lead sulfate, other basic lead sulfates, basic lead carbonates, etc., which consequently will form desired structures of Pb or PbO2 on negative or positive plates during formation.

Current: The time rate of flow of electricity, normally expressed as amperes, like the flow of a stream of water.

Cut-Off Voltage: See "FINAL VOLTAGE".

Cutting (of acid): The dilution of a more concentrated solution of sulfuric acid to a lower concentration.

Cycle: A discharge and its subsequent recharge.

Cycle Service: A type of battery operation in which a battery is continuously subjected to successive cycles of charge and discharge, e.g., motive power service.


Deep Discharge: Removal of up to 80% of the rated capacity of a cell or battery.

Direct Current (DC): A direct current is a unidirectional current in which the changes in value are either zero or so small that they may be neglected.

Discharge: The conversion of the chemical energy of the battery into electrical energy.

Discharged: The condition of a storage cell when as the result of delivering current, the plates are sulfated, the electrolyte is exhausted, and there is little or no potential difference between the terminals.

Discharge Rate: Batteries discharged to meet any time rate between 3 hours and 8 hours are considered as having been normally discharged.

Dry Charging: Manufacturing process whereby charged plates are washed free of acid and then dried.


Efficiency: The ratio of the output of the cell or battery to the input required to restore the initial state of charge under specified conditions of temperature, current rate and final voltage.

Electrolysis: Electrochemical reaction which causes the decomposition of a compound, either liquid, molten or in solution.

Electrolyte: Any substance which disassociates into two or more ions when dissolved in water. Solution of electrolyte conduct electricity and are decomposed by it. In the battery industry the word "electrolyte" implies a dilute solution of sulfuric acid.

Eelectronic Tester: An electronic device that assesses the condition of a battery through an ohmic measurement such as resistance or conductance, typically without drawing large current loads.

Electromotive Force (EMF): Electrical pressure or potential, expressed in terms of volts.

Element: Assembly of a positive plate group, a negative plate group, and separators.

Equalizing: Charge An extended charge which is given to a storage battery to insure the complete restoration of active materials in all the plates of all the cells.


Ferroresonant Charger: A constant voltage power supply containing a special transformer-capacitor combination, which changes operating characteristics as current draw is varied, so that the output voltage remains constant.

Filling Gravity: The specific gravity of acid used in the filling of batteries.

Final Voltage: The cut-off voltage of a battery; The prescribed voltage reached when the discharge is considered complete.

Finishing Rate: The rate of charge expressed in amperes to which the charging current for some types of lead batteries is reduced near the end of charge to prevent excessive gassing and temperature rise.

Fixed Resistance Discharge: A discharge in which the cell or battery is discharged through a fixed resistive load. The current being allowed to fall off as the terminal voltage decreases.

Flaming: A method used to improve the surface of a cast lead or lead alloy part or of trimmed battery sealing compound in which a flame is passed over the surface causing the material to melt and flow smoothly together.

Flat Plate: A general term referring to pasted plates.

Float Charging: Application of a recharge at a very low rate and accomplished by connection to a buss whose voltage is slightly higher than the open circuit voltage of the battery.

Flush: To add water to a cell.

Flying Leads: Any fixed terminal cable in which the terminal or plug end of the cable is unsupported and allowed to hang freely along the side of the battery.

Foot: Portion(s) of the grid projecting from the bottom edge, used for support of the plate group.

Formation or Forming Charge: An initial charging process during which the raw paste within the plates is electrochemically converted into charged active material, lead peroxide being formed in the positive plates and sponge lead in the negative plates.

Formed: Plates that have undergone formation are known by this term.

Freshening Charge: A charge given batteries in storage to replace the standing loss and to ensure that every plate in every cell is periodically brought to a full state of charge.

Full Charge Gravity: The specific gravity of the electrolyte with the cells fully charged and properly leveled.


Gang Vent: Vents for usually three adjacent cells which are connected to a common manifold. Typically used on SLl's.

Gassing: The evolution of gases from one or more of the electrodes during electrolysis.

Gelled Electrolyte: Electrolyte which has been immobilized by addition of silica powder or other gelling agent.

Glass Mat: Fabric made from glass fibers with a polymeric binder such as styrene, acrylic, furfural, starch - used to help to retain positive active material.

Gravity: Refers to specific gravity.

Gravity Drop: The number of points reduction or drop of the specific gravity of the electrolyte upon discharge of the cell.

Grid: A metallic framework employed in a storage cell or battery for conducting the electric current and supporting the active material.

Ground: The reference potential of a circuit. In automotive use, the result of attaching one battery cable to the body or frame of a vehicle that is used as a path for completing a circuit in lieu of a direct wire from a component. Today, over 99% of automotive and LTV applications, use the negative terminal of the battery as the ground.

Group: One or more plates of a type (positive or negative) which are burned to a post and strap.


Hand Stand: Manually operated casting mold into which lead or alloy is manually poured.

High Impact Rubber: See "RESIN RUBBER".

High Rate: On charge, any rate higher than the normal finishing rate.

H2S04: Chemical symbol for Sulfuric Acid.

Hydration (Lead): Reaction between water and lead or lead compounds. Lead does not react with strong solutions of sulfuric acid, but gravities lower than those found in discharged cells are apt to produce hydration. Hydration is observed as a white coating on both plate groups and separators in a cell.

Hydrometer: Device used to indicate density or specific gravity of electrolyte solutions.

Hydroset: Curing process for negative and positive plates, wherein free lead in the paste is oxidized and total free lead is reduced to a few per cent.


Indicator: Devices employed to show a battery's state of charge, or its water level.

Initial Voltage: The closed-circuit voltage at the beginning of a discharge. It is usually measured after the current has flowed for a sufficient period for the rate of change of voltage to become practically constant.

Insert: A bushing of lead or lead alloy molded or sealed into cell covers, forming the post hole, and to which the post is burned to create a creep-resistant cover-to-post seal.

Intercell Connector: Conductor of lead, lead alloy or lead plated copper which is used to connect two battery cells.

Internal Resistance: The resistance within the cell or battery to the flow of an electric current, and is measured by the ratio of the change in voltage at the terminals of the cell or battery corresponding to a specified change in current for short time intervals.


Jackstraw Mats: See "GLASS MATS".

Jar Cell: Container, made by injection molding, rota-molding, or thermo-forming.

Jar Formation: The forming of plates in the cell jar or container, after they have been assembled.

Jumper: A short length of conductor used to connect or cutout part of an electrical circuit.


Kilovolt (KV): One thousand volts.

Kilowatt (KW): One thousand watts.

Kilowatt Hours (KWH): A measure of energy or work accomplished, being 1000 watt hours.


Lamp Black: Finely powdered carbon, used as an ingredient in negative plate expander.

Lead (Pb): Chemical element used in lead-acid batteries (with sulfuric acid and other materials).

Lead Burning: Welding of lead or lead alloy parts.

Lead Hydrate: A white compound of lead of indefinite composition formed by the reaction of very dilute electrolyte or water on metallic lead or lead alloys.

Lead Oxide: A general term used to describe any of the finely divided lead oxides used to produce paste for storage batteries.

Lead Peroxide: A brown oxide of lead which is the active material in a fully formed positive plate. Its formula is PbO2.

Lead Plated: Part A metallic part that has had a thin protective layer of metallic lead electrodeposited on its surface.

Lead Sponge (Pb): The chief component of the active material of a fully charged negative plate.

Lead Sulphate (PbS04): A compound resulting from the chemical action of sulfuric acid on oxides of lead or lead metal itself.

Level Indicator: A float, mounted in a float tube, or similar indication of the electrolyte level.

Level Lines: Horizontal lines molded and/or painted near tops of battery jars, which indicate minimum and maximum electrolyte level.

Life: Number of years of satisfactory float operation or number of charge-discharge cycles for motive power operation.

Lifting Ear: An extension on the the side walls of a battery tray provided with a hole or slot, by means of which the battery can be lifted.

Litharge (PbO): A yellowish-red oxide of lead (monoxide), sometimes used in making active material.

Load Tester: An instrument that draws current (discharges) from a battery using an electrical load while measuring voltage. It determines the battery's ability to perform under actual discharge conditions.

Local Action: Local action in a battery is the loss of otherwise usable chemical energy by currents which flow within the cell of a battery regardless of its connections to an external circuit.

Loss of Charge: The capacity loss occurring in a cell or battery standing on open circuit as a result of local action.

Low Water Loss Battery: A battery that requires little to no water additions under normal operating conditions; also referred to as maintenance-accessible batteries.

Lug: Portion of grid used for support of the plate group, usually along top edge of grid, as "hanging lug." Also, tab on grid used for connection of plate to strap and other plates.


Machine Casting: A fully or semi-automatic grid or small parts casting operation.

Maintenance-Free Battery: Battery which requires no addition of water, no boost charges, etc. This typically requires a non-antimonial or low-antimonial grid alloy, sealed cell design, or low-loss venting.

Manual Discharge: Capacity test wherein the connection and disconnection of the battery and the test load are done by the operator and the disconnection is made after all cells have reached the prescribed final voltage. With fixed resistance loads, boost cells are used to keep the discharge rate fairly constant as the test cell voltages drop rapidly near the final voltage. Electronic load manual discharges generally do not require boost cells.

Marine Battery: A battery designed for shipboard installation to provide energy for cranking service and the operation of emergency lighting, alarm, and communication equipment.

Microporous Separator: Either a veneer or a grooved type separator made of any material in which the pores are numerous and microscopically small.

Mine Locomotive Battery: A cycle service battery designed to operate mine locomotive, trammer, shuttle cars, and tunnel haulage equipment.

Millivolt (MV): One thousandth part of a volt.

Modified Constant-Voltage Charge: A charge in which the voltage of the charging circuit is held substantially constant; but a fixed resistance is inserted in the battery circuit, producing a rising voltage characteristic at the battery terminals as the charge progresses.

Mold: A cast iron or steel form which contains the cavity into which molten metal is introduced to produce a casting of definite shape and outline.

Mold Coat: A preparation applied to metal molds in spray form which acts both as a mold release agent and as aninsulator against rapid heat transfer.

Mold Spray: See "MOLD COAT".

Moss: Dendritic crystals of lead (Pb) which sometimes grow at high-current density areas of negative plates, e.g. along edges, at feet, or a plate lugs. May cause a short circuit within cell.

Moss Shield: Plastic or hard rubber perforate sheet which insulates the gaps between negative plates and the positive strap, and between positive plates and the negative strap.

Motive Power Battery: A cycle service battery designed to supply the energy necessary to propel and operate electrically powered industrial trucks, street vehicles, and mine locomotives.


Negative Plate: Consists of the grid and active material to which current flows from the external circuit when the battery is discharging.

Negative Terminal: The terminal toward which current flows (as ordinarily conceived) in the external circuit from the positive terminal.


Ohm: A unit of electrical resistance.

Ohm's Law: Expresses the relationship between volts (V) and amperes (I) in an electrical circuit with resistance (R). It can be expressed as follows: V = IR [Volts (V) = Amperes (I) x Ohms (R)]. If any two of the three values are known, the third value can be calculated using the above equation.

One Shot Formation: Jar formation under conditions where end of formation specific gravity is equal to the operating specific gravity.

Open Circuit: The state of a battery when it is not connected to either a charging source or to a load circuit.

Open Circuit Voltage: The voltage at its terminals when no appreciable current is flowing.

Organic Expander: An expander formulation which typically contains barium sulfate and a lignin type organic compound, with small amount of other materials.

Oxide (of lead): A compound of lead and oxygen in one of several proportions such as gray oxide, litharge, red lead, or lead peroxide used to prepare battery paste.


Panel: Casting consisting of two or more grids which has been made simultaneously in a single mold.

Parallel Assembly: The arrangement of cells within a battery in which two or more cells are connected across a common terminal so that any current flow divides itself between the connected cells.

Parallel Connection: See "PARALLEL ASSEMBLY".

Partition: An interior dividing wall in a tray or container.

Paste: Mixture of lead oxide with water, sulfuric acid, and sometimes other ingredients.

Paste Consistency: A term used to include all of the physical characteristics of the paste density, plasticity and texture.

Pasting: Battery assembly operation wherein paste is applied to grids by hand or by a machine.

Pb: Chemical symbol for lead.

PbO: Chemical symbol for litharge.

PbO2: Chemical symbol for lead peroxide (dioxide).

Pellet: That portion of pasted material contained in a grid section framed by adjacent horizontal and vertical numbers exclusive of forming bars.

Perforated Retainer: A thin sheet of perforated plastic material installed so as to cover each face of a positive plate to prevent the loss of active material. It is normally used in conjunction with one or more layers of glass insulating material.

Peroxide: See "LEAD PEROXIDE".

Pig: A cast bar of lead or lead alloy.

Pig Lead: A grade of highly refined unalloyed lead.

Pilot Cell: A selected cell of a storage battery whose temperature, voltage, and specific gravity are assumed to indicate the condition of the entire battery.

Plate: A pasted grid, either formed or unformed.

Plate Centers: The distance between center lines of adjoining plates of opposite polarity in a cell. The plate center is, therefore, one-half of the size of a strap center upon which the plates of a like polarity are burned.

Polarity: An electrical condition determining the direction in which current tends to flow. By common usage the discharge current is said to flow from the positive electrode through the external circuit.

Polarization: The change in voltage at the terminals of the cell or battery when a specified current is flowing, and is equal to the difference between the actual and the equilibrium (constant open circuit condition) potentials of the plates,exclusive of the IR drop."

Porosity: The ratio of interstices (voids) in a material to the volume of its mass.

Positive Plates: Consists of the grid and the active material from which current flows to the external circuit when the battery is discharging.

Positive Terminal: The terminal from which current flows (as ordinarily conceived) through the external circuit to the negative terminal when the cell discharges.

Post: Terminal or other conductor which connects the plate group strap to the outside of the cell.

Post Builder: A ring shaped mold used to repair damaged battery posts.

Potential: See "VOLTAGE".

Primary Battery: A battery that can store and deliver electrical energy but cannot be recharged. A lead-acid battery is NOT a primary battery.

Primary Cell: See "CELL PRIMARY".

Pure Lead: See "PIG LEAD".



Rated Capacity: The ampere hours of discharge that can be removed from a fully charged secondary cell or battery, at a specific constant discharge rate at a specified discharge temperature and at specified cut off voltage.


Raw Plate: An unformed plate.

Rectifier: A device which converts alternating current (AC) into unidirectional current (DC) by virtue of a characteristic permitting appreciable flow of current in only one direction.

Red Lead (Pb304): A red oxide of lead used in making active material.

Reserve Capacity Rating: The time in minutes that a new, fully charged battery will deliver 25 amperes at 27°C (80°F) and maintain a terminal voltage equal to, or higher than, 1.75 volts per cell. This rating represents the time the battery will continue to operate essential accessories if the alternator or generator of a vehicle fails.

Resistance: The opposition that a conductor offers to the passage of an electrical current, usually expressed in ohms.

Resistor: A device used to introduce resistance into an electrical circuit.

Retainer: A sheet of glass mat, perforated or slotted rubber, plastic, or some other satisfactory material installed on each face of the positive plates in certain types of cells, to deter the loss of active material.

Rib: A vertical or nearly vertical ridge of a grooved separator or spacer.

Run Down: A small portion of metal that has dropped on to a plate, group or element in the course of burning. It may result in a short circuit.


Sealing: Manufacturing operation for attaching covers to jars by cement, sealing compound, or thermal fusion.

Sealing Compound: An asphalt mixture of several types differing in heat resistance, adhesion, and resistance to shearing. It is used for sealing cell covers to the jars or containers. See also "COMPOUND".

Secondary Battery: A battery that can store and deliver electrical energy and can be recharged by passing direct current through it in a direction opposite to that of discharge. A lead-acid battery is a secondary battery.

Secondary Lead: Reclaimed lead as opposed to virgin lead.

Sediment: The leady sludge or active material shed from the plates and found in the bottom of cells.

Sediment Space: The portion of a jar or container compartment beneath the element, provided to accommodate a certain amount of sediment from the wearing of the plates, without short circuiting.

Self Discharge: Loss of charge due to local action.

Separator: A device employed in a storage battery for preventing metallic contact between the plates of opposite polarity within the cell, while allowing passage of electrolyte. See also "MICROPOROUS SEPARATOR".

Separator Protector: See "MOSS SHIELD".

Shedding: Loss of active material from the plates.

Short Circuit: An unintended current-bypass in an electric device or wiring. Outside the battery a short circuit is established when a conductive path is established between the two terminals of a battery. Inside a battery, a cell short circuit is the result of contact between the positive and negative plates and will cause a cell to discharge and render the battery useless.

SLI Battery: Battery for automotive use in starting, lighting, and ignition.

Sliver: Slyver Extremely fine, parallel glass fibers used next to positive plate in retainers, to retard shedding.

Smelting: The process by which the major portion of lead and antimony are recovered from scrapped batteries and battery manufacture scrap.

Soaking: A process, whereby certain types of plates are soaked in sulfuric acid, after pasting. Soaking provides a protective surface, and also a supply of sulfate helpful in jar formation and tank formation.

Soda Ash: Sodium Carbonate (Na2C03), used to neutralize effluents containing sulfuric acid, or acid spills.

Specific Gravity (Sp. Gr. or SG): Specific Gravity is a measure of the electrolyte concentration in a battery. This measurement is based on the density of the electrolyte compared to the density of water and is typically determined by the use of a hydrometer (see "HYDROMETER"). By definition, the specific gravity of water is 1.00 and the specific gravity of the sulfuric acid electrolyte in a typical fully charged battery is 1.265-1.285. Specific gravity measurements are typically used to determine if the battery is fully charged or if the battery has a bad cell.

Spine: Cast Pb alloy conductor for tubular positive plate.

Sponge Lead (Pb): The chief material of a fully charged negative plate. It is a porous mass of lead crystals.

Stacking: Cell assembly operation wherein plates and separators are alternately piled in a burning box prior to cast-on or burning-on of straps and posts.

Stacking Fixture or Stacking Jig: The fixture or device used to stack and burn elements.

Standing Loss: The loss of charge by an idle cell or battery, resulting from local action.

Starting Rate: The number of amperes at which the charging of a storage battery may be begun without producing gassing or bubbling of the electrolyte, or a cell temperature in excess of 110°F (43°C.)

State of Charge: The amount of electrochemical energy left in a cell or battery.

Stationary Battery: A stationary battery is a storage battery designed for service in a permanent position.

Strap: Precast or cast-on piece of lead or lead alloy used to connect plates into groups and to connect the groups to the post.

Strap Center: Spacing between centers of adjacent plates in a group.

Stratification: As applied to electrolyte it is layers of high gravity acid in the lower portions of a cell, where they are out of touch with the ordinary circulation of the electrolyte and thus of no use.

Sulfated: A term used to describe any plate or cell whose active materials contain an appreciable amount of lead sulfate.

Sulfation: The formation of lead sulfate on a plate or cell as a result of discharge, self-discharge, or pickling.

Sulfuric Acid (H2S04): The principal acid compound of sulfur. Sulfuric acid of a high purity and in dilute form is the electrolyte of lead-acid storage cells.


Temperature Correction: In storage cells, the specific gravity and charging voltage vary inversely with temperature, while the open circuit voltage varies directly (though slightly) with temperature.

Terminals: The terminals of a battery are the points at which the external circuit is connected.

Terminal Cable: A length of insulated cable, one of which is connected to the terminal post of a battery, the other end being fitted with a suitable device (plug, receptacle, lug, etc.) for connection to an external circuit.

Tinning: The process of coating a metal surface with a thin layer of molten tin or tin alloy.

Tray: Steel enclosure for motive power battery cells.

Treeing: Growth of a lead dendrite or filament through a hole, crack, or large pore of a separator, whereby the cell is short-circuited.

Trickle Charge: A trickle charge of a storage battery is a continuous charge at a low rate approximately equal to the internal losses and suitable to maintain the battery in a fully charged condition.

Tubular Plate: Positive battery plate made from a cast spine and porous tubes which are filled with paste or dry oxide.

TVR: A temperature compensating voltage relay used in charging equipment.

Two Rate Charging: An automatically controlled constant current or modified constant potential charging procedure. The charge is begun at a fairly high rate and is automatically reduced to a lower rate when the counter voltage rises to a predetermined level.


Unactivated Storage Life: The period of time before a dry charged cell deteriorates to have less than a specified capacity.

Uncharged: The condition of a battery assembled with formed plates but not yet having received its initial charge, are classified either uncharged and moist, or uncharged and dry.

Uncharged and Dry: A condition in which a battery or cell may be shipped to a customer. This indicates that the battery is assembled with formed plates and dry separators without electrolyte. Filling and a charge are required.

Uncharged and Moist: A condition in which a battery or cell may be shipped to a customer. Adopted by BCI and indicates that the battery is assembled with formed plates and moist or wet wood separators, without electrolyte. Filling and a long charge are required.

Unformed: A term used to describe any plate which has not been electrically formed - it may be dry or moist, cured or uncured, soaked or unsoaked.

Useful Acid: The volume of acid above the lower edges of the plates which takes part in the discharge reactions that occur within a cell.


VRLA: Valve Regulated Lead Acid battery. AGM and Gel are the two types of VRLA batteries. These batteries have no "free" liquid electrolyte and in the cell operate on the oxygen recombination cycle, which is designed to minimize water loss. VRLA batteries feature valves that have a one-way, pressure-relief design. These low-pressure valves prohibit air entering the cell while permitting gases to vent from the cell if necessary. The pressure maintained in the battery, though only very slight, is required to facilitate the oxygen recombination reaction, which converts the oxygen generated at the positive plates back into water.

Vacuum Cell Filler: A device used to fill cells in the charging room in which a vacuum is used to withdraw the air displaced by the filling electrolyte.

Vent: An opening provided to permit the escape of gas from a cell or mold.

Vent Assembly: A cell venting device consisting of a ceramic vent stone and filler funnel assembled on a threaded or a quarter turn bayonet base.

Vent Baffle: A thin disc located in a vent cap or plug to deflect spray back into the cell.

Vent Cap: See "VENT PLUG".

Vent Plug: The piece or assembly of pieces employed to seal the vent and filling well of a cell cover except for a small hole in the plug itself which permits the escape of gas. Vent plugs are usually held in place either by threads or by a quarter turn catch (bayonet vent plug), or by a snap-in fit.

Vent Well: The hole or holes in a cell cover through which gas escapes, fluids are added or the electrolyte level is checked. The vent plug or vent assembly fits into the vent well.

Verticals: The vertical bars of members or members in a pasted plate grid.

Volt: The practical unit of measurement of electro-motive force or potential difference required to send a current of one ampere through a resistance of one ohm.

Volt Efficiency: The ratio of the average voltage of cell or battery during discharge to the average voltage during its subsequent recharge.

Voltage: The difference of potential which exists between the terminals of a cell or battery, or any two points of an electrical circuit.

Voltage Drop: The net difference in the electrical potential (voltage) when measured across a resistance or impedance (ohms). Its relationship to current is described in Ohm's law.

Voltage Range: The difference between the maximum and minimum cell voltages that exist within a battery or string of cells when all of the cells are charging or discharging.

Voltmeter: An instrument for measuring voltage.


Watering: Adding water to battery electrolyte to replace electrolysis and evaporative losses.

Watt: A measure of electric power: The product of amperes and volts.

Watthour: A measure of energy or work accomplished, being product of the rate of work in watts and the time in hours, or the product of ampere hours and the average voltage.

Watthour Capacity: The number of watthours which can be delivered under specific conditions as to temperature rate of discharge and final voltage.

Watthour Efficiency: The watthour efficiency of a storage battery is the energy efficiency expressed as the ratio of the watthour output to the watthours of the recharge.

Watthour Meter: A watthour meter is an electric motor that measures and registers electrical energy in watthours (or kilowatt hours).

Wet Shelf Life: The period of time a wet secondary cell can be stored before its capacity has fallen to the point that the cell cannot be easily recharged.

Wrapping: Assembly operation where in motive power positive plates are covered by silver, glass mat, and retainer.