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Knowledge Base

Glossary of Battery Terms and Definitions



AC (Alternating Current)

Alternating current; a flow of electrons, which regularly reverses its direction of flow. 60 cycles per second is the US standard. One cycle per second is called one Hertz (Hz). Because of how generators work the switching of peak positive current to peak negative current takes place gradually in a sine wave pattern. Cannot be stored like DC (Direct Current) in a battery.

The taking up or retention of one material by another by chemical or molecular action.

Acid (Sulfuric)
The liquid in a battery cell. Sulfuric acid (H2SO4) is diluted with water (approx. 62% water) to produce “electrolyte”, or battery acid. Pure sulfuric acid (93% acid) is far too concentrated and unstable for use in batteries. Under normal circumstances, it is not necessary to add acid to a battery, only water, to bring the electrolyte to the proper level in each cell to prevent it from drying the plates.

Active Material
A term used to describe the leadpaste” that is held in place by grids (plates) that make up a battery cell. This term usually refers to both the positive and negative plate material. The material reacts chemically to produce electrical energy by releasing free electrons. In an industrial battery, the materials are: lead peroxide (positive) and sponge lead (negative). One active material is oxidized while the other is reduced.

AC Fuse

An inline fuse between the AC power supply and the charger. All battery chargers are fused internally, in addition to external circuit breakers or disconnects required by code. These fuse are usually rated at 600vac, but are available in 250vac for chargers designed with a maximum AC voltage of 240vac. 250vac fuses are intentionally shorter than 600vac fuses so that they cannot be substituted. The voltage rating of a fuse must exceed the actual AC voltage or a fire hazard will result.

Making a dry cell functional by adding electrolyte.

Absorbed glass mat.

Air Oxidized
A charged negative plate that has been removed from electrolyte and permitted to discharge in an air atmosphere. Plates must then be recharged before they are capable of producing useful electrical energy.

A mixture of metals or a metal and a non-metal.

Alternating Current
A pulsating electric current in which direction of flow is rapidly changed, so the terminal becomes in rapid succession positive, then negative. Abbreviated AC.

A type of generator used in automobiles to produce electric current.

Ambient Humidity
The average humidity of the surroundings.

Ambient Temperature
The average temperature of the surroundings.

An instrument for measuring electrical current.

Current carrying capacity in amperes. The maximum amperage a given wire size can safely deliver.

Ampere (Amp)
The unit of electrical current equal to the steady state current produced by one volt applied across a resistance of one ohm. Or, a count of how many electrons pass a given point in one second. A closed circuit is necessary for current flow.


The strength of an electrical current expressed in amperes (amps).

A measure of the volume of electricity, being one ampere for one hour. It is used to express battery capacity, and is registered by an ampere-hour meter; it can be obtained by multiplying the current in amperes by length of time that the current is maintained. You can convert amp-hrs to waft hours by multiplying amp-hrs by the systems battery voltage.

Ampere-Hour Capacity
The quantity of electricity measured in ampere-hours (Ah) that may be delivered by a cell or battery under specified conditions.

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

Ampere-Hour Meter
An instrument that registers the quantity of electricity in ampere-hours.

The electrode in an electrochemical cell where oxidation takes place. During discharge, the negative electrode of the cell is the anode. During charge, the positive electrode is the anode.

Antimonial Lead Alloy
A commonly used alloy in battery castings. The percentage of antimony varies from 1/2% to 12%. Other substances are present in small quantities, either as inescapable impurities or by design to improve the properties of the cast part.

A hard, brittle, silver white metal with a high luster from the arsenic family.

1. Combining various parts into a finished battery. 2. Any particular arrangement of cells, connectors and terminals to form a battery.

Automotive Battery
SLI battery of 3 or 6 cells used for starting, lighting and ignition of cars, trucks, buses, etc.

Average Voltage

A storage battery’s average value of voltage during a period of charge or discharge.



Two or more electrochemical cells electrically interconnected in an appropriate series/parallel arrangement to provide the required operating voltage and current levels. Under common usage, the term "battery" is often also applied to a single cell if it is used alone. A battery cell contains an anode, a cathode, and the electrolyte. The nominal voltage of a lead-acid cell is 2 volts.

A cylindrical cell design utilizing an internal cylindrical electrode and an external electrode arranged as a sleeve inside the cell container.

The ribbed supporting structure in the bottom of a battery container that provides sediment space under
the elements, thereby preventing short circuits.

Welding together two or more lead or lead alloy parts such as plates, straps, and connectors.

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

Burning Stick
A lead or lead alloy stick used as a supply of joining material in lead burning.




C-Rate (also see Hourly Rate)
Discharge or charge current, in amperes, expressed in multiples of the rated capacity. For example, C/10 discharge current for a battery rated at 1.5 Ah is: 1.5 AH/I 0 = 150 mA (A cell's capacity is not the same at all discharge rates and usually increases with decreasing rate.)

A metallic element highly resistant to corrosion, used as a protective plating on certain 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 is sometimes used for battery parts in place of antimonial lead alloys.

The total number of active material or watt-hours that can be withdrawn from a fully charged cell or battery under specified conditions of discharge.

Capacity Offset
A correction factor applied to the rating of a battery if discharged under different C-rates from the one rated.

Capacity Retention (or Charge Retention)
The fraction of the fall capacity available from a battery under specified conditions of discharge after it has been stored for a period of time.

Capacity Test
A test that discharges the battery at constant current at room temperature to a cutoff voltage of usually 1.70 volts/cell.

Forming a molten substance into a shape by introducing the material into a mold and allowing it to solidify.

A metallic item, such as one or more grids, straps or connectors, formed by pouring a molten substance into a mold and allowing it to solidify.

Cast-On Strap
A multiple connector that had been cast onto the plates directly in a combination mold/burning jig; contrasts with burning of plates and prefabricated straps.

The electrode in an electrochemical cell where reduction takes place. During discharge, the positive electrode of the cell is the cathode. During charge in a rechargeable battery, the negative electrode is the cathode.

The basic electrochemical unit used to generate or store electrical energy. One 2-volt unit connected in series or parallel to create a battery.

Cell Mismatch
Cells within a battery pack that contain different capacity and voltage levels.

Cell Reversal
The stronger cells of a battery (several cells connected in series) impose a voltage of reverse polarity across a weaker cell during a deep discharge.

Charge / Charging
The conversion of electrical energy, provided in the form of electrical current from an external source, to restore the chemical energy in a cell or battery.

Charge Control
Technique for effectively terminating the charging of a rechargeable battery.

Charge Rate

The amount of energy per unit of time, which is being added to the battery. Commonly expressed as a ratio of the battery's rated capacity to charge in relation to the time of charge duration. If you have a battery with a storage capacity of 1,000 amp-hrs and your charger is rated at 50 amps then your charge rate is expressed as C/20 (1,000 / 50 ).

A storage cell at maximum ability to deliver current. The positive plates contain a maximum of lead oxide and a minimum of lead sulfate, and the negative plates contain a maximum of sponge lead and a minimum of sulfate, and the electrolyte is 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.

The process of converting electrical energy to stored chemical energy. In the lead-acid battery, it converts lead sulfate in the plates to lead peroxide (positive) or lead (negative).

Charging Rate
The current, expressed in amperes, at which a battery is charged.

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

Closed-circuit Voltage (CCV)
The potential or voltage of a battery when it is discharging or charging.

A process that utilizes a series of heavy discharges and recharges on a battery to assure optimum performance.

Constant Current
A battery discharge regime whereby the current drawn during the discharge remains constant.

Constant Current Charge
A charge that maintains the current at a constant value. For some types of batteries this may involve two rates, called a starting and a finishing rate.

Constant Potential Charge or Constant Voltage Charge
A charge that holds the voltage at the terminals at a constant value.

Constant Power
A battery discharge regime whereby the current during the discharge increases as the battery voltage decreases.

Constant Resistance
A battery discharge regime whereby the resistance of the equipment load remains constant throughout discharge.

Continuous Test
A test in which a battery is discharged to a prescribed end point voltage without interruption.

The amount of electricity transported by a current of one ampere flowing for one second.

The lid of an enclosed cell, generally made of the same material as the container and through which the posts and vent plug extend.

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

Travel of electrolyte up the surface of electrodes of other parts of the cell above the level of the main body of the electrolyte.

Chemical conversion process that changes lead oxides and sulfuric acid to mixtures of basic lead sulfates, basic lead carbonates, etc., which consequently forms the desired structures of lead or lead sulfate on negative and positive plates during formation.

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

Current Collector
An inert structure of high electrical conductivity used to conduct current from or to an electrode during discharge or charge.

Current Density
The current per unit active area of the surface of an electrode.

Current Drain
The current withdrawn from a battery during discharge.

Current Limiting Chargers
A charger that keeps the charge current constant during the charge process but allows the voltage to Fluctuate (typically used on NiCd and NiMh chargers).

Cutoff Voltage
The battery voltage at which the discharge is terminated. The cutoff voltage is specified by the battery manufacturer and is generally a function of discharge rate.

Cutting (of acid)
Dilution of solution of sulfuric acid to a lower concentration, or “specific gravity”.

A sequence where a charged battery is discharged and recharged. One complete charge / discharge sequence of the battery. Forklift batteries are rated to last for 1500 to 2000 cycles.

Cycle Life The number of cycles under specified conditions that are available from a secondary battery before it fails to meet specified criteria as to performance.

Cycle Service
Battery operation that continuously subjects a battery to successive cycles of charge and discharge, e.g., motive power service.

Cylindrical Cell
The positive and negative plates are rolled up and placed into a cylindrical container (as opposed to stacking the plates in a prismatic cell design).




DC (Direct Current)

Direct current; a flow of electrons that flows only in one direction, negative to positive. PV's produce DC power. DC can be stored electrochemically in a battery.


Deep Cycle Battery

A battery specifically made to have up to 80% of its energy capacity removed and replaced repeatedly for many cycles. The plates of this type of battery are much thicker than are starting battery's plates.

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

Depth of Discharge (DOD)
The ratio of the quantity of electricity (usually in ampere-hours) removed from a battery to its rated capacity.

The opposite of absorption, whereby the material retained by a medium or another material is released.

Dielectric Test
An electric test performed on jars, containers and other insulating materials to determine their dielectric breakdown strength.

The intermingling or distribution of particles or molecules of a liquid.


A one-way check valve allowing electricity to flow in one direction.

Direct Current
Electrical current that flows in one direction only. Batteries produce direct current as the current flows from a negative to a positive source.

The conversion of the chemical energy of a battery into electrical energy, and the withdrawal of the electrical energy into a load.

Discharge Rate
The rate, usually expressed in amperes, at which electrical current is taken from the battery.

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

The current withdrawn from a battery during discharge.

Dry Cell
A cell with immobilized electrolyte. The term "dry cell" is often used to describe the Leclanche cell.

Dry Charged
Battery plates that have been subjected to the dry charging process.

Dry Charging
Manufacturing process in which tank-formed battery plates are washed free of acid and then dried.

Dumb Battery
Straight battery pack without internal circuits enabling communication between the battery and the user.

Duty Cycle
The operating regime of a battery including factors such as charge and discharge rates, depth of discharge, cycle duration, and length of time in the standby mode.




Discharge or charge power, in watts, expressed as a multiple of the rated capacity of a cell or battery that is expressed in watt-hours. For example, the E/10 rate for a cell or battery rated at 17.3 watt-hours is 1.73 watts. (This is similar to the method for calculating C-Rate.)

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

Electric Current
The movement of electrons along a conductor.

Electrochemical Equivalent
Weight of a substance that is deposited at an electrode when the quantity of electricity which is passed is one coulomb

The site, area or location at which electrochemical processes take place.

Electrode (Electrolyte) Potential
The difference in potential between the electrode and the immediately adjacent electrolyte, expressed in terms of some standard electrode potential difference.

Electrochemical reaction that causes the decomposition of a compound.

Diluted sulfuric acid. The medium, which provides the ion transport (see ion) mechanism between the positive and negative electrodes of a battery cell.

Electromotive Force (EMF)
The force that causes electrons to flow because of a difference in electrical potential (measured in volts).

Negatively charged particle that orbits the nucleus of an atom. Electrons have 1/1837 the mass of hydrogen (the lightest atom), and are subatomic.

An assembly of a positive plate group, negative plate group and separators.

End Gravity
The specific gravity of a cell at the end of a prescribed discharge.

End Voltage Cutoff
The prescribed voltage at which the discharge (or charge, if end-of-charge voltage) of a battery may be considered complete.

The output capability of a cell or battery, usually expressed in watt-hours.

Energy Density
The ratio of the energy available from a battery to its volume (Wh/L) or weight (Wh/kg).

A separator folded and wrapped around a battery plate during assembly.

Equalizing Charge
A controlled overcharge, or extended charge, that restores all cells in a battery to 100% state of charge (SOC). Ensures complete restoration of active materials in all the plates of the cells. The controlled overcharge of a seemingly fully charged battery (many cells within the battery already are fully charged) to bring the weaker cell (s) up to full charge. Should be accomplished every 30 days, or as needed. You can determine unequal cells with a hydrometer (should be within 15 points lowest to highest reading), or you can check voltage readings across each cell and compare them (should be within .05 volts lowest to highest readings

An ingredient in the negative paste that delays shrinking and solidifying of the sponge lead of the finished plate, thereby enhancing negative plate capacity.




Fast Charge
The fast-charger detects the state of charge and switches to trickle charge when full-charge is reached.

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

Filling Gravity
The specific gravity of acid used to fill 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, in amperes, to which charging current is reduced near the end of the charge for some types of batteries to prevent gassing and temperature rise.

Fixed Resistance Discharge
Discharge of a cell or battery through a fixed resistive load, the current being allowed to fall off as the terminal voltage decreases.

Float (Float Charge)
A low rate of charge that will maintain a battery at a full SOC without over charging the battery. The use of batteries in which they are charged by an application to be ready for use if the primary power to the application fails. Also called standby or backup.

Float Charge
Similar to trickle charge. Compensates for the self-discharge on a SLA battery

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

Float Plate
A pasted plate.

Flooded cells

Those where 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. The most familiar example of a flooded lead-acid cell is the 12-V automobile battery.

Projections from the grid at the bottom edge, used to support the plate group.

Forced Discharge
Discharging a cell in a battery, by the other cells or an external power source, below zero volts into voltage reversal.

Formation or Forming Charge
An initial charging process that electrochemically converts the raw paste of the plates into charged active material, lead peroxide in the positive plates and sponge lead in the negative plates.

Plates that have undergone formation.

Freshening Charge
A charge given batteries in storage to replace the standing loss and ensure that every plate is periodically brought up to full charge to prevent sulfation.

Full Charge Gravity
Specific gravity of the electrolyte when cells are fully charged and properly leveled.

Device used for cutting off an electrical current in the event of an abusive condition. Also see AC Fuse.




The separation of hydrogen and oxygen that occurs as the battery approaches 100% SOC. It can also happen if the battery is under heavy load. This gas is very explosive when in concentrations of more than 2 PPM (parts per million).

A device that produces an electric current through magnetism.

Glass Mat
Fabric made from glass fibers with a polymeric binder such as styrene or acrylic, which is used to help retain positive active material.

Gravimetric Energy
The ratio of the energy output of a cell or battery to its weight (Wh/kg). This term is used interchangeably with specific energy.

Specific gravity.

Gravity Drop
The number of point’s reduction or drop of specific gravity of the electrolyte from cell discharge.

A metallic framework used in a battery for conducting electric current and supporting the active material or active mass.

To connect to the earth or some conductor, which takes the place of the earth.

One or more plates of one type – positive or negative – burned to a post or strap.




Sulfuric Acid.

Hazardous Waste
Waste which is classified as "hazardous" (i.e.. potentially harmful to the environment) by the government.

Hertz (Hz)
The standard unit of frequency. A frequency of one complete cycle per second is a frequency of one hertz.

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

Hourly Rate
A discharge rate, in amperes, of a battery, which will deliver the specified hours of service to a given cutoff voltage.

Hydration (Lead)
Reaction between water and lead or lead compounds. Gravities lower than those found in discharged cells are apt to produce hydration, which appears as a white coating on plate groups and separators in a cell.

A device used to measure the specific gravity of the electrolyte in a cell.

Curing process for plates that oxidize the lead paste, reducing free lead to a few percent of total.




Impedance Intermittent Test
Used in terms of the battery's internal resistance a test during which a battery is subjected to alternate periods of discharge and rest according to a specified discharge regime.

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

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

Intercell Connector
Conductor of lead or lead alloy used to connect two battery cells.

Internal Impedance
The opposition exhibited by a circuit element (cell or battery) to the flow of an alternating current (a/c.) of a particular frequency as a result of resistance, induction and capacitance.

Internal Resistance (IR)
The opposition exhibited by a circuit element to the flow of direct current (D.C.). In a cell, the internal resistance is the sum of the ionic and electronic resistances of the cell components.


A device that conditions and converts DC to AC. There are modified sine wave (MSW) inverters, which are in reality closer to square wave than a sine wave. MSW inverters have from 30 to 40% Total Harmonic Distortion (THD), or distortion from a pure sine wave. The utility grid averages, about, 3% THD. A Trace SW inverter has from 3 to 5%, and an Exeltech inverter has 1 to 2% THD.


An atom or a group of atoms that has acquired a net electric charge by gaining or losing one or more electrons. A "positive ion" is an atom with fewer electrons, and a "negative ion" is an atom with more electrons.

IR Drop
A voltage drop associated with the electrical resistance (R) of a battery or current flow (I). The voltage drop is the product of the current (in amperes) and the resistance (in ohms).




Housing, or container, for one or more cells.

Jar Formation
Forming of plates in the cell jar, vs. tank formation.

A short length of conductor used to connect or cut out part of an electrical circuit.




Kilovolt (kV)
One thousand volts.

Kilowatt (kW)
One thousand watts.

Kilowatt Hours (kWh)
Unit of energy (1000 watts) to perform work. If a 100 watt light is on for 10 hours it has consumed 1 kWh of energy.



Lead (Pb)
Chemical element used in lead-acid batteries.

Still the most popular battery used today its main application is for the automobile industry, although it has a growing number of other applications. Its advantages are low cost, high voltage per cell and good capacity life. Disadvantages are poor low temperature characteristics, it is relatively heavy, and it cannot be left in a discharged state for too long without being damaged. Related Batteries: Absorbent Glass Matt (AGM) Gel/Gel cell Sealed Lead-acid.

Lead Burning
Welding of lead or alloy parts.

Lead Hydrate
A white lead compound formed by reaction of very dilute electrolyte or water and metallic lead or lead alloys.

Lead Oxide
A general term for any of the lead oxides used to produce batteries.

Lead Peroxide
A brown lead oxide, which is the positive material in a fully formed positive plate.

Lead Plated Part
Hardware that has a thin protective layer of lead electrode deposited on the surface.

Lead Sponge
The chief component of the active material of a fully charged negative plate.

Lead Sulfate
A compound that results from the chemical action of sulfuric acid on oxides of lead or on lead metal.

Level Lines
Horizontal lines molded or painted near tops of battery containers indicating maximum and minimum electrolyte levels.

Limiting Current
The maximum current drain under which the particular battery will perform adequately under a continuous drain. The rate is based on whatever drain rate reduces the running voltage to 1.1 volts.

Load Current (Load)
The discharge current provided by a battery, or drawn by a battery-powered device. Can also refer to any device consuming energy. Usually expressed in terms of watts or amps.

Local Action
A battery’s loss of otherwise usable chemical energy by currents that flow within the cell of a battery regardless of its connection to an external circuit. Also known as Self Discharge.

Loss of Charge
Capacity loss in a cell or battery standing on open circuit as a result of local action.

A portion of the grid used for support of the plate group, usually a hanging lug on the top edge of the grid. Also, a tab on the grid used for connection of plate to strap and other plates.




Machine Casting
A fully or semiautomatic grid or small parts casting operation.

MF (Maintenance Free Battery)
A VRLA sealed absorbed glass mat (AGM) battery.

Manual Discharge
Capacity test in which the operator disconnects the battery from the test load 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.

Memory Effect
A phenomenon in which a cell or battery operated in successive cycles to the same, but less than full, depth of discharge temporarily loses the rest of its capacity at normal voltage levels.

Microporous Separator
A veneer or grooved-type separator made of any material that has many microscopically small pores.

Midpoint Voltage
The voltage of a battery midway in the discharge between the start of the discharge and the end voltage.

One thousandth of an ampere.

Refers to battery capacity. A 1/1000th of an amp, e.g.: 1.0Ah = 1000mAh.

One thousandth of a volt.

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

A cast iron or steel form used to produce a casting of definite shape or outline.

Mold Coat
A spray applied to metal molds that acts as a release agent and an insulator against rapid heat transfer.

Lead crystals that can grow at high current density areas of negative plates— along edges, at feet or at plate lugs— and cause short-circuiting.




A terminal or electrode, which has an excess of electrons.

Negative Plate
The grid and active material that current flows to from the external circuit when a battery is discharging.

Negative Terminal
The terminal from which current flows through the external circuit to the positive terminal when the cell discharges.

Nickel Cadmium
One of the most proven and historically most widely used rechargeable batteries. Very dependable and "robust" but contain cadmium and have relatively low capacity when compared to other rechargeable systems. Very good high rate discharge capabilities make them very popular in high drain applications such as power tools.

Nominal Voltage
The characteristic operating voltage or rated voltage of a battery.




A measure of resistance that causes one volt to produce a current of one ampere.

Ohm’s Law

Expresses the fundamental relationship between voltage, current, and resistance. Current (Amps, or I) in a circuit equals Voltage (E) divided by Resistance (Ohms, or R):

I = E / R or Amps = Volts / Ohms

By using simple algebra, Ohm's law can be rearranged as:

E = I x R or Volts = Amps x Resistance

It can also be rearranged as: R = E / I or Resistance = Volts / Amps

The current flow in a circuit depends on both the voltage of the source (battery, or PV) and the resistance of the circuit.

Oil of Vitriol
Concentrated commercial sulfuric acid, abbreviated OV or O.V.

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

Open-Circuit Voltage
The difference in potential between the terminals of a cell or multiple cells in a battery when the circuit is open (no load connected).

The forcing of current through a cell after all the active material has been converted to the charged state, that is, continued charging after reaching 100 percent state-of-charge.

Over discharge
The process of discharging a cell or battery beyond its cutoff voltage and possibly into voltage reversal.

A battery operates through electrochemical reactions called oxidation and reduction. These reactions involve the exchange of electrons between chemical species. If a chemical species loses one or more electrons, this is called oxidation. The opposite process, the gain of electrons, is called reduction.

Oxide (of lead)
A compound of lead and oxygen in one of several proportions used to prepare battery paste.




A casting consisting of two or more grids made simultaneously in a single mold.

Term used to describe the interconnection of cells or batteries in which all the like terminals are connected together (positive to positive, negative to negative. Results in increased capacity, but the voltage remains the same.

The phenomenon by which a metal, although in conditions of thermodynamic instability, remains indefinitely unattacked because of modified or altered surface conditions.

Chemical symbol for lead.

Chemical symbol for litharge.

Chemical symbol for lead peroxide.

The portion of pasted material contained in a grid section framed by adjacent horizontal and vertical members exclusive of forming bars.

See Lead Peroxide.

A cast bar of lead or lead alloy.

Pig Lead
A grade of highly refined, unalloyed lead.

A pasted grid.

Plate Centers
Distance between centerlines of adjoining plates of opposite polarity in a cell. One half the size of a strap center upon which the plates of like polarity are burned.

In electricity, the condition of being positive or negative.

The lowering of the potential of a cell or electrode from its equilibrium value caused by the passage of an electric current.

The ratio of open spaces or voids in a material to the volume of its mass.

A terminal or electrode, which has a shortage of electrons.

Positive Plates
The grid and active materials of a storage battery from which current flows to the external circuit when the battery is discharging.

Positive Temperature
A thermally reactive device, which becomes highly resistive at a specific Coefficient (PTC) temperature or current.

Positive Terminal
The terminal that current flows toward in the external circuit from the negative terminal.

Terminal or other conductor that connects the plate group strap to the outside of the cell.


The amount of work being done. The unit measurement of power is called a Watt (W). Electric power is simply the product of voltage times current.
Watts = Volts x Amps  or  Volts = Watts / Amps and also as Amps = Watts / Volts

Primary Battery
A battery which is not intended to be recharged and is discarded when the battery has delivered all of its electrical energy.

Prismatic Cell
The positive and negative plates are stacked rather than rolled as done in a cylindrical cell.

Pulse Current
A periodic current drain of higher than normal drain rates.

Pure Lead
Pig Lead.








Rapid Charge
A charge time that is between slow charge and fast charge.

Rate of Charge
See Starting Rate and Finishing Rate.

Rated Capacity
The number of ampere-hours a battery can deliver under specific conditions (e.g., rate of discharge, end voltage, temperature); usually specified by the battery manufacturer.

Raw Plate
An unformed plate.

Rechargeable Battery
A battery, which, after discharge, may be restored to the fully charged state by the passage of an electrical current through the cell in the opposite direction to that of discharge.

A device that converts alternating (ac) current into unidirectional (dc) current because of a characteristic that permits appreciable flow of current in only one direction.

Red Lead
A red oxide of lead used in making active material.

Reference Electrode
Electrode used to measure acid concentration or plate state of charge.

The degree to which the flow of electrons is opposed by the material the electrons must pass through, or opposition to the flow of current. Unit of measurement is called an Ohm, stated as R, or by the Greek letter omega. All conductors have some resistance; this is necessary because if a conductor had no resistance the connection would be a short circuit with excessive current flow. Insulators have high resistance and conductors have low resistance. Bad connections (loose, corroded, or dirty) have high resistance and can result in little current flow and heat.

A device used to introduce resistance into an electrical circuit.

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

The changing of the normal polarity of a battery due to Over discharge.

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




Safety Vent
A venting mechanism designed into a cell, which activates under specific conditions of abuse to relieve internal pressure.

Sealed Batteries

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. During charge, a lead-acid battery generates oxygen gas at the positive electrode. Sealed lead-acid batteries are designed so that the oxygen generated during charging is captured and recombined in the battery. This is called an oxygen recombination cycle and works well as long as the charge rate is not too high. Too high of a rate of charge may result in case rupture, thermal runaway, or internal mechanical damage. The valve-regulated battery is the most common type of sealed battery. It was developed for stationary and telecommunication battery applications. 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 lead-acid 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. Sealed type batteries are often avoided for backup power source applications for several reasons. One reason is that the state of charge of sealed type batteries cannot be ascertained by the usual specific gravity measurement. Reliable alternative methods to measure the state of charge for sealed type batteries are under development. A second reason is their sensitivity to high temperatures.

Secondary Battery
A battery that can be recharged and reused many times.

Secondary Lead
Reclaimed as opposed to virgin lead.

Secure Waste Landfill
A landfill designed for disposal of normal household trash but which meets government standards designed to protect the environment.

The sludge or active material shed from plates that drop to the bottom of cells.

Sediment Space
The portion of a container beneath the element; sediment from the wearing of the plates collects here without short-circuiting.

The tendency of all electrochemical cells to lose energy (capacity) due to internal chemical reactions within the cells. Also called local action.

An ionic permeable electronically non-conductive spacer or material, which prevents electronic contact between electrodes of opposite polarity in the same cell.

The interconnection of cells in such a manner that the positive terminal of the first is connected to the negative terminal of the second, and so on, resulting in increased voltage. Note that the current stays the same when series interconnecting.

Series Cells
All cells in a battery other than pilot cells. They are so called because the cells are usually connected in series.

Series Parallel Connection
Cells arranged in a battery so two or more strings of series connected cells, each containing the same number of cells, are connected in parallel; this increases battery capacity.

Service Life
The period of useful life of a battery before a predetermined end-point voltage is reached.

Shelf Life
The duration of storage under specified conditions at the end of which the battery still retains the ability to give a specified performance.

Short Circuit
An unwanted electrical connection between a negative and positive source. Short circuits can damage the battery and equipment and can cause sparks or fire.

Short-Circuit Current
The initial value of the current obtained from a battery in a circuit of negligible resistance.


A low value resistor used in parallel with a meter to increase the amount of current the meter can measure.

A primary battery (non-rechargeable) it is a major contribution to miniature power sources, and is well suited for hearing aids, instruments, photoelectric exposure devices and electronic watches. These cells are primarily made in the smaller button sizes.

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

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

Slow Charge
Typically an over-night charge lasting about 14 hours at a charge current of 0.1C. Battery does not require instant removal when fully charged.

Smart Battery
Battery with internal circuit enabling some communication between the battery and the user. Some batteries feature a capacity indicator only; others offer an external bus to interface with the equipment the battery power and the intelligent charger.

The primary process for recovering lead and antimony from scrapped batteries and scrap from battery manufacture.

A manufacturing process following pasting that soaks certain types of lead plates in sulfuric acid. This provides a protective surface and also sulfate helpful in container and tank formation.

Soda Ash
Sodium Carbonate (Na2CO3) used in neutralizing sulfuric acid in spills or effluents.

Soft Cell
A cell whose voltage rises above its defined boundaries during charging. This voltage rise may be caused by high cell impedance as a result of prolonged battery storage, very cold battery temperature or lack of electrolyte.

Shedding of active material, usually from positives, during formation due to incomplete or improper plate curing.

Specific Energy
The ratio of the energy output of a cell or battery to its weight (Wh/kg). This term is used interchangeably with gravimetric energy density.

Specific Gravity (SG or SPGR)
The weight of the sulfuric acid electrolyte compared to water or the ratio of a liquid's density to the density of water. Because sulfuric acid is denser than water, the difference can be measured with a battery hydrometer (tool that measures SPGR) and the approximate state of charge can be determined.

Sponge Lead (Pb)
A porous mass of lead crystals and the chief material of a full-charged negative plate.

A cell assembly operation, alternately piling plates and separators in a burning box prior to attachment of straps and posts.

Standard Battery
Any of Conventional, YuMicron or YuMicron CX batteries consisting of flooded electrolyte and cell accessible construction.

The use of batteries in which they are charged by an application to be ready for use if the primary power to the application fails. Also called float or backup.

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

Starting Rate
A beginning charging rate that does not produce gassing or temperatures in excess of 110°F.

Starved Electrolyte

Starved electrolyte either on Glass fibers (AGM, Absorptive Glass Mat) or as a Gel (Gel technology). Starved electrolyte allows internal gas circulation.

State of Charge
The capacity remaining in a battery. A ratio, expressed in percent, of the energy remaining in a battery in relation to its capacity when full.

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

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

Layering of high specific gravity electrolyte in lower portions of a cell, where it does not circulate normally and is of no use.

A plate or cell whose active materials contain an appreciable amount of lead sulfate.

Growth of lead sulfate crystals in Lead-Acid batteries, which inhibits current flow. Sulfation is caused by storage at low state of charge. During recharge, a current flow of electrons is forced through the battery in the opposite direction of discharge by the application of voltage across the battery's terminals. The chemical bond between the lead and the sulfate ions is broken, and the sulfate ion is released back into the electrolyte solution. When all the sulfate ions have been removed from the plates and are in the electrolyte, the battery is considered fully charged.

If the battery is not recharged, and lead sulfate ions stay on the plates long enough (about three to four weeks), the sulfate becomes hardened crystals and is difficult to remove. This is called sulfation. Storage capacity of the battery is reduced when the plates are sulfated. Sulfation can even render an otherwise good battery useless.

Sulfuric acid (H2SO4)
The principal acid compound of sulfur, sulfuric acid in dilute and highly pure form is the electrolyte of Lead-Acid storage cells.




Tack Burn
A shallow burn used to tack together two lead parts.

Tank Formation
Electrolytic processing of plates prior to assembly in large tanks of sulfuric acid.

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

Temperature Cutoff
A protective or safety device (e.g., thermostat, PTC, etc.) which senses temperature in a battery and opens or cuts off the electrical circuit if the specified temperature is exceeded, thus preventing a further rise in temperature due to the charge or discharge of a battery.

A device at the end of a cell or wire for making a connection to an adjoining cell or wire.

Terminal Cable
A length of insulated cable, one end connected to the battery terminal post, and the other fitted with a plug, receptacle, lug or other device for connection to an external circuit.

A temperature sensitive switch.

Top Pour
A method of casting in which molten metal is poured, usually by hand, into a top gated mold.

Top-Off Charge
A low rate charge following the main charge, designed to ensure maximum capacity.

Steel Housing for one or more 2-volt cells.

Growth of a lead dendrite or filament through a crack or hole of a separator, short-circuiting the cell.

Trickle Charge
A charge at a low rate, balancing losses through local action and/or periodic discharge, to maintain a cell or battery in a fully charged condition.

A time / voltage relay used in charging equipment. Typically allows battery to charge to 80%, then times out after 3 hours to complete charge.




A plate that has not been electrolytically formed.

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




An opening that permits the escape of gas from a cell or mold.

Vent Cap
The seal for the vent and filling well of a cell cover, containing a small hole for escape of gas.

Vent Well
The hole or holes in a cell cover that allow fluids to be checked, electrolyte to be added, and gas to escape. The vent plug fits into the vent well.

The members in a plate grid.

The unit of measurement of electromotive force, being the force needed to send a current or one ampere through a conductor with a resistance of one ohm. Or, the electromotive force, which will cause current to flow. A standard definition of the volt is: an emf of 1 Volt is necessary to move a current of 1 Amp through a 1-Ohm resistor. A voltmeter measures the difference in potential between two points. It may be helpful to think of voltage to electricity flow as pressure is to water flow.

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

A unit of measuring electrical pressure. Batteries are rated in DC (Direct Current) volts.

Voltage Delay
Time delay for a battery to deliver the required operating voltage after it is placed under load.

Voltage Depression
An abnormal drop in voltage below expected values during the discharge of a battery.

A system that incorporates a mechanical identifier on batteries and devices to ensure only batteries of the correct voltage are connected to the device.

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

Voltage Regulator
A device that regulates the output of a generator or alternator by controlling the current and voltage.

Voltage Reversal
The changing of the normal polarity of a battery due to over discharge.

An instrument for measuring voltage.

Volumetric Energy Density
The ratio of the energy output of a cell or battery to its volume (Wh/L).

VRLA (Valve Regulated Lead-Acid)
Sealed batteries, which feature a safety valve venting system, designed to release excessive internal pressure, while maintaining sufficient pressure for recombination of oxygen and hydrogen into water.




Wall-less Design
A battery design where the structural support for the cells is formed by an open plastic framework.

Adding water to battery electrolyte to replace loss from electrolysis and evaporation, to bring it to the Proper Level.

Water Level
The level of the acid/water solution (electrolyte) in a battery cell. Maintaining the correct water level is essential to achieving maximum battery life, productivity and return on investment.

A unit of power or measurement of energy, arrived at by multiplying the voltage by the amperage. Power is the rate of using energy to do work. Amperage x voltage = watts. Watts are a constant; if the voltage is higher then the amperage will be lower to produce the same amount of wattage or vise versa.

A common measurement of energy produced in a given amount of time arrived at by multiplying the voltage by the amp hours.

Watt-hour Capacity
The number of watt-hours a storage battery can deliver under specific conditions of temperature, rate of discharge and final voltage.

Watt-hour Efficiency A storage battery’s energy efficiency expressed as ratio of watt-hour output to the watt-hours of the recharge.

Watt-hour Meter
An electric motor that measures and registers electrical energy in watt-hours.

Wet Shelf Life
The time a wet secondary cell can be stored before its capacity falls to the point that the cell cannot be easily recharged.











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Last Updated: Wednesday, October 10, 2018 - 3:33 AM Eastern Time.