Battery Terms and Definitions

Last updated: 7/6/2021

Active MaterialThe chemically reactive material at the positive or negative electrode that engages in the charge and discharge reactions.
Ampere Hours (Ah)The number of minutes a battery can maintain a useful voltage under a specified load.
AnodeAn electrode through which electric current flows into a polarized electrical device.
BatteryOne or more cells connected to form one unit supplying voltage and having provisions for external connections. Batteries produce electrons through chemical reactions.
CapacityThe ability of the battery or cell to supply current.
CathodeAn electrode through which electric current flows out of a polarized electrical device.
CellElectrochemical device capable of storing electrical energy.
Cell Jar / Cell CaseThe vessel holding the cell components.
Charge CollectorThe structure within the electrode that provides a current path to/from the active material.
Cold Cranking Amp (CCA)The rating used in the battery industry to define a battery’s ability to start an engine in cold temperatures. It is the number of amps a new, fully maintained and charged battery can deliver at 0°F for 30 seconds, while holding a voltage of at least 7.2 volts for a 12 volt battery. The higher the CCA, the more higher the starting power of the battery
Continuous Discharge Rating (CDR)Also known as an amp limit, this is the maximum amount of current (amps) that you can continuously draw before the battery heats up to unsafe levels (typically 75&degC / 167°F).
CycleIn a rechargeable battery a cycle consists of a charge followed by a discharge.
Dry Cell BatteryBatteries that can be mounted in any position because they are completely sealed & won’t leak acid. Most of these bare either AGM (absorbed glass mat) or Gel type batteries.
Duty CycleThe use pattern for a battery including charge, overcharge, rest and discharge.
ElectrodesAn electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte or a vacuum.
ElectrolyteAny substance containing free ions that behaves as an electrically conductive medium, usually when in a solution. Because they generally consist of ions in solution, electrolytes are also known as ionic solutions, but molten electrolytes and solid electrolytes are also possible.
Energy DensityA term used for the amount of energy stored in a given system or region of space per unit, volume, or mass.
FloatMaintaining a battery on a continuous, long-term charge, normally for batteries that sit unused for longer periods.
Flooded CellA cell where the electrodes are immersed in a pool of electrolyte.
Gas RecombinationRecycling gases formed within the cell rather then venting them to the atmosphere. This mainly pertains to sealed lead acid battery.
Leclanché CellA French electrical engineer chiefly remembered for his invention of the Leclanché cell, one of the first modern electrical batteries and the forerunner of the modern dry cell battery.
LifeThe length of acceptable performance received from a battery, measured in years or in charge/discharge cycles.
Maintenance-Free BatteryA battery that where no electrolytes can be added.
Open-Circuit VoltageVoltage of a battery with no load applied to it.
Operating VoltageVoltage of a battery under load.
OverchargeThe application of charge current after the battery has reached full charge.
OxidationDescribes the loss of electrons or an increase in oxidation state by a molecule, atom or ion.
ParallelInterconnecting cells or batteries by joining all like terminals which doubles battery amp hours/run time & cca (cold cranking amps).
PlatesLead plates used within a battery to hold a charge.
Primary CellIs any kind of electrochemical cell in which the electrochemical reaction is not reversible. A common example of a primary cell is the disposable battery.
ReductionPart of a reduction-oxidation (redox) reaction in which atoms have their oxidation number (oxidation state) changed.
Reserve CapacityThe capacity of a battery, measured in minutes, to keep a vehicle operating if the charging system fails.
Sealed CellA cell where all reactants are retained within the container. May contain a vent for release during abusive overcharge.
Secondary BatteryA backup or spare battery used to replace the primary battery when discharged.
Self-DischargeIs a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes. Self-discharge decreases the shelf-life of batteries and causes them to have less charge than expected when actually put to use.
SeparatorMaterial which provides separation and electrical insulation between plates of opposite polarity.
SeriesInterconnecting cells or batteries by connecting the positive terminal of one unit to the negative terminal of the next, which doubles the battery voltage.
WoundInterior cell construction in which plates are coiled inside.

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