Battery Terms and Definitions

Absorbent Glass Mat — (AGM) A separator technology used in some sealed lead-acid batteries in which the glass-mat separator absorbs 100% of the electrolyte. Because of the immobilized electrolyte, an AGM battery will not leak or spill and does not require water addition.

Ah — Ampere-Hour.

AGM — Absorbent Glass Mat.

Acceptance Test — A capacity test of a new battery at either constant current (expressed in amperes) or constant power (expressed in watts) rate to determine if it meets the user's specification or manufacturer's ratings.

Accumulator — See Battery.

Active Material — The chemical paste that adheres to the positive (+) and negative (-) electrodes in a battery and reacts with the sulfuric acid to produce a current.

Alternating Current — (AC) An electric current that varies periodically in magnitude and direction, measured in hertz. A battery does not deliver alternating current.

Ampere — (Amp) The unit of measure for the amount of current that is flowing through a circuit. Ampere (Amp) is the unit of current flow equal to one coulomb per second. Ampere hours(Ah), also known as Amp-hours, is the unit of measure used for comparing the capacity or energy content of batteries with the same output voltage. For most batteries, it defines the battery's C rate. For automotive (Lead Acid) batteries the SAE defines the Amp-hour capacity as 20 times the current delivered for a period of 20 hours when the battery is discharged at 1 twentieth of the C rate until the cell voltage drops to 1.75 Volts. Strictly, 1 Ampere hour is the charge transferred by one amp flowing for one hour, namely, 1Ah = 3600 Coulombs. The true capacity of any battery is its energy content and this is measured in WattHours (Wh). It is the battery's Amp-hour capacity multiplied by the battery voltage 

Ampere-Hour — (Ah) (Amp-Hour) The product of multiplying the ampere flow by the time over which it flows. Example: A battery delivering 10 amps for 20 hours = 10 amps x 20 hours = 200 AH.

Alkaline Battery — A non-rechargeable, dry-cell battery — such as a AA, AAA, C, D or 9-volt battery — that uses alkaline aqueous solution for its electrolyte. It has a higher capacity than some other types of dry-cell cells.

American National Standards Institute — (ANSI) An organization, sponsored by the National Electric Manufacturers Association (NEMA), that establishes policy and standards regarding cell sizes, terminals, and testing procedures.

Anode — The positive (+) terminal of an electrolyte battery. The negative (-) terminal of a primary cell battery.

ANSI — American National Standards Institute.

Antimony — (Sb) A metal alloyed with lead to improve the strength and castability of the grids. Antimony usually is used only in lead-acid batteries in cycle service, and where make-up water may be added. It is not generally used in VRLA batteries due to its relatively high gasSing rate.lead-acid

Application — The equipment in which a battery is used.

Autonomy — The length of time during which a fully charged battery can supply power to the load with no contribution from a
the primary or auxiliary power source (also known as reserve time).

Average Drain — The average current withdrawn — i.e., the drain — from a cell or battery during discharge, usually approximated by calculating the current at 50% depth of discharge.

Average Voltage — The average of the battery terminal voltage during discharge.

Battery — Two or more cells connected in series that produces and stores electrical energy as a result of a chemical reaction. Lithium-ion Battery, Nickel Cadmium Battery, Air Cell, Energy Storage System, Nickel Metal Hydride Battery, Other Rechargeable Batteries/Storage Technologies 

Battery Rack — A structure on which individual batteries are installed. Racks act to support the batteries and maybe seismically rated.

Battery Charge — See State of Charge.

Boost Charge — Charging the battery at a maximum allowable voltage for a defined period to ensure the battery is fully charged.

Bunsen Valve — A type of pressure relief valve based on a rubber cap or ring, which, under normal conditions, closes an opening in a cell and temporarily deflects to provide pressure relief upon the buildup of excessive cell pressure within a cell.

Cable — An insulated group of flexible twisted wires used to interconnect individual or groups of batteries.

Cabinet Battery System — An enclosed metal case containing a complete battery system of individual series-connected batteries.

Capacitor — An electrical component capable of storing and releasing a charge via the action of an electrostatic field between two parallel metal plates. Typically used to smooth the AC ripple voltage which may appear at the output of a DC power source.
Electric Double-Layer Capacitor, Hybrid Capacitor, Electrolytic Capacitor, Lithium-ion Capacitor, Redox Capacitor, Other Capacitors 

Capacity — The ability of a fully charged battery to deliver a specified quantity of electricity (AH) at a given rate (amps) over a definite period of time (hours).

Capacity Test — A constant current or constant power load is applied to a battery under standard temperature conditions to determine its actual ampere-hour or watt-hour capacity at the particular discharge rate and end voltage.

CC — Constant Current.
CP — Constant Power.

CR — Constant Resistance.
CV — Constant Voltage.
CCA — Cold Cranking Amperes.
CCV — Closed-Circuit Voltage.

Cell — An individual electrochemical device composed of two electrodes of dissimilar metals (active materials) and an electrolyte. When the electrodes are immersed in an electrolyte, the cell will produce a voltage differential between electrodes. When connected to electrodes, the cell will provide a current through an external circuit.

Cell (Dry) — Typically consists of two electrodes of dissimilar material isolated from one another electronically in the immobilized electrolyte. See also Dry-Cell Battery.

Cell (Flooded) — Typically consists of a set of positive (+) plates, negative (-) plates, liquid electrolyte, separators, and casing.

Cell Mismatch — The condition of a battery pack that contains cells with significant variations in voltage or capacity. In a liquid-electrolyte battery, cell mismatch may be determined using a hydrometer.

Cell Reversal — When the typical positive (+) to negative (-) polarity of a cell is reversed due either to incorrect connection of the charger or the discharge of the lowest capacity cell in a series-connected group of cells beyond the recommended endpoint voltage.

CEMF — Counter Electromotive Force.

Charge — The ampere-hours capacity removed during discharge and to maintain the battery in 'float' or standby mode.

Charge Efficiency — The ratio of the ampere-hours removed during discharge to ampere-hours recharge required to restore 100% state of charge multiplied by 100.

Charge Retention — The capacity retained following specific storage conditions and a specified period of time.

Charger — A Direct Current (DC) power supply used to both supply current to a battery to restore the ampere-hours capacity removed during discharge and to maintain the battery in 'float' or standby mode.

Charging — The process of restoring the ampere-hours removed from a battery during discharge. Approximately 108% to 115% of the ampere-hours discharged must be restored to attain a full state of charge.

Charging Voltage — The voltage used to overcome a battery's internal resistance and to recharge the battery.

Choke — See Inductor.

Circuit — The path followed by a current.

Circuit Breaker — An electromechanical device that will automatically open a circuit when excessive current is flowing in the circuit.

Closed Circuit — A completed circuit through which current can flow when a switch in the circuit is either 'On' or 'Closed.'

Closed-Circuit Voltage — (CCV) The voltage of a battery when the cell or battery is under a specific discharge load and time interval.

Cold Cranking Amperes — (CCA) The number of amperes a battery can supply at O°F (-17.8°C) for 30 seconds to an endpoint voltage of 1.2 volts per cell.

Conditioning — (1) The process of restoring capacity to a nickel-cadmium or nickel-metal-hydride battery by deeply discharging and recharging the battery multiple times. (2) The method of preparing a lead-acid battery for a set of standard electrical tests by a precise charge regime.

Conductance — (mho) A measure of a material's ability to conduct current. It is the mathematical reciprocal of electrical resistance.

Conductor — A material with the capability to carry a current or flow of electrons.

Constant Current — (CC) An electron flow through a conductor (a current) that does not vary significantly from a pre-set value.

Constant Resistance — (CR) A situation during discharge in which the resistance of the application remains constant.

Constant Voltage — (CV) A voltage that does not vary significantly from a preset value.

Constant Power — (CP) DC power in watts is equal to the product of voltage multiplied by the current in amperes.

Constant-Current Battery Charger — A battery charger with output current that stays relatively constant as the battery state of charge increases.

Constant-Current Discharge — A discharge in which the current drawn from the battery remains constant.

Constant-Voltage Battery Charger — A voltage-regulated battery charger that allows a decrease in charging current as of the battery state of charge increases.

Container — The vessel or receptacle that contains the cell element and electrolyte. Often referred to as a jar.

Continuity — The indication that a circuit is completed between two points; continuity does not exist in an open circuit.

Continuous Test — A battery test in which the battery is continuously discharged until it reaches a predetermined voltage.

Corrosion — A destructive chemical reaction with a reactive metal that forms a new compound. Battery terminals can be subject to corrosion.

Counter Electromotive Force — (CEMF) The voltage that is produced within the battery, mainly by chemical means, that opposes the charging voltage.

Cranking Battery — An SLI battery.

Current — (I) The flow of electrons or amperes through a conductor.

Current Drain — The current withdrawn from a battery during discharge.

Cutoff Voltage — The voltage at the end of useful discharge. When the battery voltage is below this level, the connected equipment will not operate, and operation is not recommended.

Cycle — One sequence of battery activity, which is a battery discharge followed by a complete recharge.

Cycle Life — The number of times a battery can be discharged and re-charged under a specific set of conditions until the battery capacity declines to a specified minimum value (usually 80% of the battery's rated capacity).

Cycling — The repeated charge/discharge cycle of a battery. Some batteries are rated according to their ability to cycle.

Deep Cycle — A battery discharge consuming more than 80% of the battery's rated capacity.

Deep Discharge — The discharge of the battery to below the specified cutoff voltage before the battery is replaced or recharged.

Depth of Discharge — (DOD) The percent of rated capacity to which a cell or battery is discharged. It is the reciprocal of a battery's state of charge. Example: a battery that has a depth of discharge of 45% has a state of charge of 55%.

Diode — A semiconducting device that restricts the flow of current to one direction. It is commonly used to convert AC current to DC current.

Direct Current — (DC) An electron flow through a conductor that travels in only one direction. A battery produces a DC voltage and current.

Discharge — The operational state during which the battery is delivering current to a load. The rate of discharge is the number of amperes or watts being delivered.

Discharge Rate — The rate at which current is drawn from a battery, usually expressed in amps.

Discharged — The state of a battery when it has less than a 100% state of charge.

Discharging — The withdrawal of electrical energy from a cell or battery, usually to operate connected equipment. A battery is discharging when it delivers current.

Drain — Withdrawal of current from a cell or battery. Often referred to as discharging.

Dry-Charged — An individually formed plate or a completed lead-acid battery drained of all electrolyte that has undergone a special drying process. The plate or battery can then be stored for a period of time with minor degradation due to sulfation. At a later date, the plate or battery is activated by the addition of the electrolyte and application of a special charging regimen.

Dry-Out — Resulting from significant overcharging, dry-out refers to the total loss of electrolyte due to gassing.

Dual Rate Charger — A charger with two output voltages used to charge batteries. One is usually set at the lower recommended float voltage, while the other is usually placed at the higher recommended equalization voltage.

Duty Cycle — The time duration and use frequency during which a battery is drained. It is affected by such factors as charge and discharge rates, depth of discharge, length of cycle, and length of time in standby mode.

Discharge Energy: Cumulative value of present channel discharge energy 

dV/dt: The first-order change rate of voltage (V/s). What is the meaning of dV? dV = V-Vmax,  V represents the present measured voltage value.  Vmax represents the measured maximum voltage during a test.  dV is designed to be used as the termination condition for the charge process of Ni-MH or Ni-Cd cells.  For a Ni-MH or Ni-Cd cell, a complete charge process is signaled by the drop in voltage of the cell after the cell voltage reaches its maximum value

dI/dt: The first-order change rate of current

E — Volt.

e — Electron.

Efficiency — The ratio of the output power of a device to the power applied. Efficiency = power out / power in

Electric Circuit — A conductive path through which current can flow.

Electricity — The flow of electrons through conductive materials and devices.

Electrode — A device that moves electrons in and out of a cell, such as the positive and negative plates of a lead-acid battery.

Electrolysis — The chemical process that breaks down the water in the electrolyte, releasing hydrogen from the cathode and oxygen from the anode.

Electrolyte — Any acidic, basic, or salt solution capable of conducting current.

Electrolyte Reserve — When a battery has more electrolyte acid available than that required to adequately react the active materials of the plates. When fully discharged, there will still be sufficient conductive acid available in the electrolyte to carry significant recharge current.

Electrolyte Starved — When a battery has insufficient electrolyte acid available to fully react all the active material of the plates. When fully discharged, the acid is almost fully consumed from the electrolyte, and the first recharge current acceptance may be reduced.

Electromotive Force — (EMF) Voltage.

Electron — (e) A negatively charged particle that orbits the nucleus of an atom. When displaced from the orbit, the electron is free to flow as an electric current.

Element — The assembled set of positive and negative plates and separators that comprise a cell when inserted into a container.

EMF — Electromotive Force.

End of Life — (EOL) The point in the operational life when a battery can only deliver 80% or less of rated capacity.

End Voltage — At a specific discharge rate, the voltage under load when the discharge is considered complete. Also called the end of discharge voltage.

EOL — End of Life.

Equalize Charge — A charging method that equalizes the specific gravity or voltage levels of individual cells in a battery or a group of batteries connected in series.

Float Charge — A low, constant-current or constant-voltage charge that compensates for the self-discharge of a battery normally used in a standby application.

Float Service — An application where the battery is continuously connected to a charger and is seldom required to deliver any significant current to the load.

Float Voltage — The voltage at which the battery is maintained on float charge.

Floating Ground — A system in which there is no voltage reference between the battery terminals and the ground.

Flooded Cell — A lead the acid battery with a liquid electrolyte, or a vented cell where the gasses produced through overcharging are vented directly to the atmosphere.

Freshening Charge — The charging of batteries in storage to assure they are maintained in a near maximum state of charge and to ensure there is no deterioration of the battery plates due to self-discharge and sulfation. This process is usually performed using the recommended equalization or cycle service charging voltage.

Frequency — The number of times that a periodic function, such as current or voltage, repeats the same sequence of values within a unit of time. Measured in hertz.

Fuse — A circuit overload protective device containing a metallic component that melts when prescribed current limits are exceeded, thus opening the circuit.

Fusible Link — A type of fuse in a circuit consisting of a reduced number of strands of wire held together by solder.

Gassing — The production of gas in a battery due to the chemical reaction during recharging.

Gassing Voltage — The charging voltage at which the cell will start to generate and expel gas.

Gelled Electrolyte — A liquid electrolyte with fumed silica added as an immobilization technique. The result is a spill-proof battery capable of supporting an oxygen recombination cycle.

Gravity — See Specific Gravity.

Grid — A lead-alloy framework that supports the active material of a battery plate and conducts current.

Ground — A large conducting body, such as the metal frame of a vehicle, used as a common return for an electric circuit and as an arbitrary zero of potential.

Ground Cable — The cable which connects the ground - e.g., the metal frame of the vehicle - to the battery, normally to the negative (-) terminal.

Ground Fault Detection — The monitoring of voltage from a battery's terminals to ground in order to identify whether a short circuit to the ground exists.

Group — An assembly of plates with like polarity (either positive or negative) connected in parallel via a strap within a cell.

Group Size — The physical dimensions of a battery. BCI assigns letters and numbers for North American battery size types. All group-size-24 batteries, for example, have similar container dimensions, terminal orientation, and terminal types.

Half Cell Voltage — The voltage of the positive and negative plates with respect to a third electrode, such as a mercury-mercuric sulfate probe, when immersed in the electrolyte.

Hertz — (Hz) A unit of frequency equal to one cycle per second.

High Rate Discharge — A discharge at a current greater than that of the one-hour discharge rate. Typically this is the one through 30-minute rates.

Hydration Short — When a cell is over-discharged and not recharged within a short period, the plates' lead sulfate, which is more soluble in water than in the acid, can go into solution with the low specific gravity electrolyte, and then penetrate the separators. Upon recharging, the lead sulfate in the separators is converted to lead, and a short circuit develops through the separator.

Hydrogen — A colorless, odorless gas given off at the negative plate of a lead-acid battery due to electrolysis of the water in the electrolyte during periods of the overcharge. Hydrogen can reach an explosive level at a 4% concentration in air.

Hydrometer — An instrument used to measure the specific gravity of a liquid electrolyte.

Hz — Hertz.

I — Current.

Immobilized Electrolyte — An electrolyte made motionless by the use of a gel additive or AGM separator. This ensures that there is no free liquid electrolyte and allows the battery to be used in any orientation without spillage.

Impedance — (Z) The total opposition that a battery offers to the flow of alternating current. Impedance is a combination of resistance and reactance.

Inductor — (L) Numerous turns of wire, usually wrapped around some type of iron core, which present inductive reactance to the flow of an AC current. Also referred to as a choke, an inductor is typically used in circuits to eliminate the AC ripple from the output of a DC power source.

Initial Charge — The charge applied to a battery when it is first installed. The initial charging voltage is typically the same as that used for equalization.
Initial Drain — The current that a cell or battery supplies when first placed on load and also referred to as the starting drain.

Initial Voltage — The minimum voltage to which a battery first declines when a current is drawn from the battery.

Insulator — A material — such as rubber, some plastics, and glass — that is highly resistant to conducting electricity.

International ElectroChemical Commission — (IEC) A worldwide organization that establishes standards in the electrical and electronic fields.

Inter-cell Connector — An electrically conductive wire, bus bar or strap used to connect two individual cells in series or parallel.

Internal Resistance — (Ri) (Internal Ohmic Measurement) The opposition to direct current flow within a battery, which causes a drop in closed-circuit voltage proportional to the battery's discharge rate.

Ion — An atom with more or fewer electrons than required to remain in equilibrium. Out of balance, the atom becomes negatively or positively charged and can act as a current carrier. Ions, rather than electrons, are the current carriers of an electrolyte.

IR Drop — The reduction in the total voltage appearing at the terminals of a battery when a load is applied. It is the product of the battery's current, expressed in amperes (A or I), multiplied by the internal resistance, expressed in ohms.

Jar — See Container.

Kilo — (k) Metric prefix for 1000. For example, one kilovolt would be 1000 volts.

Kilowatt — (kW) One thousand watts.

Kilovolt Ampere — (kVA) One thousand volt-amperes. The output of a UPS is typically rated in volt-amperes.

Lead-acid Battery — A storage battery with an active material of lead and lead peroxide and with an electrolyte solution of water and sulfuric acid. Maintenance-free, low-maintenance, and gel-cell batteries are types of lead-acid batteries.

Lead Oxide — (PbO) Particles of oxidized lead are combined with water and sulfuric acid and made into a paste. They are then applied to the lead-acid battery grids. Later, the lead oxide is converted to active material through the formation process.

Lead Dioxide — (PbO2) The active material of the positive plate in a battery.

Lead Sulfate — (PbO4) The product resulting from the discharge of the active materials of the plates. This may be the result of an active discharge of the battery or local action.

Lithium-Ion Battery — A rechargeable battery with a very high capacity for its size and weight compared to other rechargeable batteries.

Load — The amount of current supplied by a battery to the device being powered.

Load Bank — An assembly of resistive elements connected in parallel or series-parallel to present a load of pre-determined amperes to the battery. There are both DC and AC rated load banks, and they may not be used interchangeably.

Load Tester — An instrument that discharges a battery using an electrical load while measuring voltage. It determines the battery's ability to perform under actual operating conditions.

Local Action — A reaction between the sulfuric acid electrolyte and the active materials of the plates resulting in the slow discharge of the plates leading to the formation of lead sulfate on the plates and consumption of the acid in the electrolyte. Evidence of local action includes declining electrolyte specific gravity and terminal voltage. The condition can be reversed by the application of a freshening charge to the battery or by a continuous float charge. Local action is increased at elevated temperatures.

Low-Maintenance Battery — Normally a lead-acid battery, it may require periodic water addition under normal service conditions. A dual-alloy battery, it typically uses a low antimony lead alloy in the positive (+) grid and a calcium-lead composite in the negative (-) grid.

mA — MilliAmp.

mAH — Milliamp-hour.

Maintenance-Free Battery — A battery that does not require water addition under normal service conditions. Both positive (+) and negative (-) grids are made of lead/calcium.


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Marine Cranking Amps — (MCA) The current a battery produces for 30 seconds at 32°F without the terminal voltage declining to below 1.2 volts per cell.

Mho — A unit of electrical conductance equal to the reciprocal of resistance. Mho is the backward spelling of Ohm.

Memory Effect — A condition that is created when a NiCad or NiMH battery is partially discharged and recharged repeatedly, causing a loss of capacity.

Micro — (u) Metric prefix meaning 1/1,000,000. One microampere is equal to 0.000001 amperes.

Milliamp — (mA) Metric prefix meaning 1/1,000. One milliampere is equal to 0.001 amperes.

Milliamp-hour — (mAh) Metric prefix meaning 1/1,000. One milliamp-hour is equal to 0.001 amphours.

Monoblock — A battery consisting of two or more series-connected cells in a single container. A 12 volt battery is a monoblock comprising 6 series-connected 2 volt cells.

Monocell — A single-cell battery. Several monocells may be connected to provide increased voltage or capacity.

Mossing — Mossing can occur invented cells where sloughed active, positive material will circulate in the electrolyte and reform as harmful material as it touches and adheres to the negative plate. It can result in shorted cells when it occurs at the top of the plates and bridges the separators. This process is also referred to as treeing.

Multicell — See Monoblock.

Negative — (-) Normally refers to the negative (-) battery terminal, which is the point from which electrons flow during discharge. The negative (-) terminal cap or cable is typically black, designating negative (-).

Negative Plate — The gray plate in a lead-acid battery. It contains the metallic lead active material and expels .the electron current during discharge.

Negative Terminal — NEG(-) The terminal of a battery connected to the negative plates and to which the external load and charger connections are made.

NiCad — Nickel-cadmium battery.

Nickel-Metal-Hydride Battery — (NiMH) A form of rechargeable battery used in portable devices such as camcorders, cell phones, cordless phones, and laptops. It provides a higher capacity than a nickel-cadmium battery but is designed to perform at a lower discharge rate.

NiMH — nickel-metal-hydride battery

Nominal Voltage — The approximate open-circuit voltage of a cell or battery. For example, the nominal voltage of a lead-acid battery is 2 volts per cell, but the actual voltage is higher and is a function of the electrolyte specific gravity.
OCV — open-circuit voltage.

Ohm — A unit of electrical resistance. When one volt is applied across a resistor with one ohm of resistance, a current of one ampere will flow through the resistor.

Ohms Law — (I=V/R)Equation used in circuit analysis, which states that the current flowing through a circuit is proportional to the voltage applied and is inversely proportional to the resistance of the circuit.

Open Circuit — An interrupted conductive path or circuit. The circuit's switch would be in the OFF position, and the current could not flow.

Open-Circuit Voltage — (OCV) The no-load voltage of a cell or battery measured with a voltmeter.

Open Battery Rack — A-frame on which individual batteries are mounted. They are totally exposed to the view for ease of visual inspection and maintenance.

Overcharging — Continued charging of the battery after it has reached 100% capacity, or charging at higher than recommended float charge voltage. Overcharging reduces service life and can damage the battery.

Over-Discharge — Discharge of a battery to a voltage lower than that recommended for the particular discharge rate.

Oxygen Evolution — The production of oxygen gas at the positive plate as a result of the electrolysis of water in the electrolyte during overcharging.

Oxygen Recombination Cycle — In a VRLA battery, the process whereby the oxygen evolved at the positive plate diffuses through the separator to react with the negative plate and suppresses water loss. This is one of the characteristics that distinguishes the VRLA battery from vented lead-acid batteries.

Parallel Circuit — A circuit in which the current has more than one path to follow. In this configuration, two batteries of equal rating are wired together positive (+) to positive (+) and negative (-) to negative (-). In parallel, the RC (Reserve Capacity) and CCA (Cold Cranking Amps) double while the voltage remains the same as the weakest individual battery.

Parallel Connection — Individual cells or batteries of the same voltage interconnected with all the Pos (+) terminals connected together and all the Neg (-) terminals connected. The capacities of the individual units are cumulative.

Pasting — The process of applying a paste consisting of lead oxide, water, and sulfuric acid to the lead alloy grid of the plate.

Pasted Plate — A lead alloy grid to which the active materials, in a paste form, have been applied.

Performance Capacity Test — A capacity test performed under the same conditions as the original acceptance capacity test to determine what, if any, degradation of capacity has occurred. Any capacity below 80% of the rating is indicative of the need to replace the battery. See Acceptance Capacity Test.

Pilot Cells — Cells within a battery selected to represent the state of the entire battery.

Plate — A composite of a grid framework and the chemically active material.

Plante Plate — Named for its 1859 developer, Gaston Plante & this is one type of positive plate used in a lead-acid battery. It is a solid lead plate on which the active materials are electrochemically formed rather than having been pasted onto the plate.

Polarity — The particular state of a battery terminal, either positive (+) or negative (-).

Polarization — The electrical potential reduction of electrodes, typically arising from the prolonged or rapid discharge of the battery.

Positive — (+) Normally refers to the positive (+) battery terminal, which is the point to which electrons in the external circuit flow during discharge. Sometimes the positive (+) terminal cap or cable is red, designating positive (+).

Positive Plate — The positive (+) electrodes of a battery composed of lead peroxide on a grid.

Potential Difference — Voltage or electromotive force (EMF).

Power — During discharge, the battery output power in watts is equal to the terminal voltage multiplied by the output current in amperes.

Power Factor — (p.f.) A term related to AC circuits. The ratio of real power to apparent power. pf = true power / apparent power

Primary Battery — A cell or battery designed to deliver its rated capacity once and then be discarded; it is not designed to be recharged. Primary batteries include alkaline, heavy-duty, and general-purpose batteries.

Rate Sensitivity — Typically refers to battery performance under various discharge loads, with the operating voltage being the defining characteristic.

Rated Capacity — The ampere-hours or watt-hours a battery delivers under standard conditions at a specified discharge rate to a specified endpoint voltage.

RC — Reserve Capacity.

Recombinant — The process in which the oxygen formed at the positive (+) plate diffuses to the negative (-) plate, reacts with the lead, and suppresses water loss. In a recombinant (immobilized electrolyte) chemistry battery, gassing is recombined within the sealed battery so that water addition is unnecessary.

Rectifier — As a circuit component, it converts AC power to DC power. It is also used to describe a DC power supply used to charge the battery and power the critical load.

Reconditioning — See conditioning.

Rectify — to convert alternating current into direct current.

Recycling — The recovery of reusable lead, acid, and plastic from spent lead-acid batteries.

Reserve Capacity — (RC) A measurement of the minutes a battery can supply 25 amperes to an endpoint voltage of 1.75 volts per cell.

Resistance — The opposition to the free flow of current in a circuit.

Resistor — A circuit component used to oppose the flow of current.

Retainer — A glass fiber mat attached to the ribbed side of a separator and placed against the positive plate in the assembled element. A retainer's function is to hold the sloughed positive active material in place and thus improve the plate cycle life.

Reversed Polarity — The changing or shifting of the normal polarity of a battery, which commonly occurs when battery cables or charging cables are connected backward.

Ri — Internal resistance.

Sb — See Antimony.

Sealed Battery — A maintenance-free battery with nonremovable vent caps.

Secondary Battery — Any battery that is designed to be recharged, such as lead-acid, NiCad, and nickel-metal-hydride batteries.

Secondary Cell — A rechargeable cell.

Sediment — The material shed from the positive and negative plates in a vented (liquid electrolyte) cell. It settles to the bottom of the cell in the space under the plates.

Seismic Rack — A reinforced battery stand with cell retaining rails designed to withstand the forces imposed during an earthquake.

Self-Discharge — The discharge that occurs in a battery while it is not in use. The higher the temperature, the greater the rate of self-discharge.

Self-Discharge Rate — The rate at which a cell or battery loses its capacity when standing idle.

Separator — An insulating material, usually rubber, plastic, or glass fibrous matting, used to isolate the positive and negative plates and prevent them from touching one another or shorting out.

Series Circuit — A circuit in which the current has only one path to follow. In this configuration, two batteries of equal rating are wired together positive (+) to negative (-). In series, the battery voltage increases while the RC and CCA remain the same as the weakest individual battery.

Service Life — The period of time during which the battery continues to meet the requirements of the application and is at least 80% of the rated capacity.

Shelf Life — The amount of time a cell or battery will retain a specified percent of its rated capacity, typically under ambient storage conditions. Interstate's superior rotation service ensures that batteries are fresh on the shelf.

Short Circuit — A short circuit in a battery cell may be permanent enough to discharge the cell and render the battery useless.

SLI — Starting, Lighting, and Ignition battery. An SLI battery's design is optimized for high rate cranking current delivery and is used in automotive applications. It is not designed to provide long life in continuous float service.

Slow Charge — Charging at a rate of about 5-10% of a battery's rated capacity. Example: 50 AH battery x 10% = 5-amp charge

Smart Battery — A battery with internal circuitry designed to communicate information, such as capacity remaining, to the user, or other parts of the application's circuit.

Smart Charger — A charger that fully discharges a NiCad battery and a NiMH battery before recharging it to prevent a memory effect from occurring.

Specific Gravity — Specific Gravity (SG), or gravity, is a measure of the density of a liquid as compared to that of water, which has an SG of 1.000. For example, pure sulfuric acid has a specific gravity of 1.835. Lead-acid battery electrolyte is a mixture of water and sulfuric acid, which typically has a specific gravity of between 1.200 and 1.300.

Standard Conditions — Varying between countries, a widely recognized and specific set of temperatures, and endpoint voltages by which a battery's output is measured. In North America, standard conditions are 77°F (25°C) to an endpoint voltage of 1.75 volts per cell. In some countries, the standard terms are 68°F (20°C) to an endpoint voltage of 1.8 volts per cell.

Standard Discharge Rate — A function of the intended application, the acceptance rate at which the battery delivers current.

Stationary Battery — A battery used in a fixed position and usually mounted in a rack, cabinet or stand, as opposed to a battery used in a mobile application.

State of Charge — (SOC) The condition of a battery in terms of rated capacity remaining at a given point in time. Expressed as a percentage, the state of charge is the quotient of the remaining ampere-hours (AH) in a battery divided by the rated capacity of the cell.

Strap — The lead casting that joins the element plates of like polarity in parallel.

Stratification — A condition in which the concentration of acid is higher at the bottom of the battery than at the top. Generally caused by continued undercharging.

Sulfuric Acid — (H2SO4) The acid that, when mixed with water, is the electrolyte in a lead-acid battery.

Sulfation — The accumulation of lead sulfates (white salts) on the plates of a lead-acid battery. When enough plate area has sulfated, the battery will not be able to provide enough current and will typically need to be replaced.

Switch — A mechanical device used for opening and closing a circuit.

Taper Charge — A cycle service charging technique using an unregulated charger. As the current acceptance of the battery declines, the charger's output voltage rises.

Temperature Cutoff — A device, such as a thermostat, that senses battery temperature and opens the battery circuit when the temperature reaches a certain point.

Terminal — A connection point on a device or component, e.g., a battery terminal.

Terminal Voltage — The voltage at the battery terminals.

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Thermal Runaway — A condition where a battery generates more heat than can be dissipated and eventually melts the plastic jar. This is often the result of float charging in a warm environment with either little ventilation or shorted cells.

Trickle Charging — Charging at a prolonged rate of 1-2 amps, this is typically used for smaller batteries — e.g., motorcycle, lawn, and garden — or occasionally is erroneously used for keeping large automotive batteries fully charged when they are not in use.

Uninterrupted Power Supply  — (UPS) Battery-powered system that provides standby power if the primary power is interrupted.

Unwanted Resistance — Any resistance — e.g., corrosion and faulty connections — found in a circuit that is not designed into the circuit.

UPS — Uninterrupted Power Supply.

Valve — Provides for release of excessive pressure developed within the cell and prevents the entry of the outside atmosphere into the cell.

Valve-Regulated Lead-acid Battery — (VRLA) A lead-acid battery that is sealed except for a one-way valve that opens to the atmosphere when the internal gas pressure in the cell exceeds the atmospheric pressure by a pre-selected amount. VRLA batteries are sometimes called recombinant batteries.

Vent — An opening was allowing for the free escape of gasses from the lead-acid battery. It may have a condensing chamber to minimize the exhaust of electrolyte mist and a flame arresting device to prevent the ignition of gasses within the cell by an outside source but is otherwise open to the atmosphere.

Vented Battery — A battery in which the gaseous products of electrolysis and evaporation are allowed to escape into the atmosphere as they are generated. These batteries are commonly referred to as flooded batteries.

Volt-Ampere — (VA) The product of output AC voltage multiplied by AC current.

Volt — (V) A unit of force sufficient to carry one ampere of current through one-ohm resistance.

Volt-ohm-meter — (VOM) Multimeter.

Voltage — Also called electromotive force (EMF), it is the electrical pressure that forces electron flow in a complete circuit.

Voltage Drop — The net difference in the electrical potential (voltage) when measured across a resistance (ohms). Its relationship with the current is described in Ohm's Law.

Voltage Regulator — A device that limits the charging voltage in a circuit.

Voltmeter — An instrument used to measure the voltage in a circuit or the state of charge of a battery by measuring its open-circuit voltage.

Watt — A unit of power. It is the product of voltage (expressed in volts) multiplied by current (expressed in amperes). For example, 120 volts x 3 amperes = 360 watts.

Watt-Hour — A unit of work. The product of power, expressed in watts, multiplied by the time, expressed in hours, over which the power is produced.

Z — Impedance.

Zinc Chloride — A chemistry used in some heavy-duty batteries.

Zinc-Air Cell — A dry-cell battery system that uses oxygen and catalyzed carbon as the cathode and zinc as the anode to produce electricity.

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