Battery Terms and Definitions

Last updated: 10/22/2009

Active Material The 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.
Anode An electrode through which electric current flows into a polarized electrical device.
Battery One or more cells connected to form one unit supplying voltage and having provisions for external connections. Batteries produce electrons through chemical reactions.
Capacity The ability of the battery or cell to supply current.
Cathode An electrode through which electric current flows out of a polarized electrical device.
Cell Electrochemical device capable of storing electrical energy.
Cell Jar / Cell Case The vessel holding the cell components.
Charge Collector The 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
Cycle In a rechargeable battery a cycle consists of a charge followed by a discharge.
Dry Cell Battery Batteries 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 Cycle The use pattern for a battery including charge, overcharge, rest and discharge.
Electrodes An electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte or a vacuum.
Electrolyte Any 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 Density A term used for the amount of energy stored in a given system or region of space per unit, volume, or mass.
Float Maintaining a battery on a continuous, long-term charge, normally for batteries that sit unused for longer periods.
Flooded Cell A cell where the electrodes are immersed in a pool of electrolyte.
Gas Recombination Recycling gases formed within the cell rather then venting them to the atmosphere. This mainly pertains to sealed lead acid battery.
Leclanché Cell A 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.
Life The length of acceptable performance received from a battery, measured in years or in charge/discharge cycles.
Maintenance-Free Battery A battery that where no electrolytes can be added.
Open-Circuit Voltage Voltage of a battery with no load applied to it.
Operating Voltage Voltage of a battery under load.
Overcharge The application of charge current after the battery has reached full charge.
Oxidation Describes the loss of electrons or an increase in oxidation state by a molecule, atom or ion.
Parallel Interconnecting cells or batteries by joining all like terminals which doubles battery amp hours/run time & cca (cold cranking amps).
Plates Lead plates used within a battery to hold a charge.
Primary Cell Is any kind of electrochemical cell in which the electrochemical reaction is not reversible. A common example of a primary cell is the disposable battery.
Reduction Part of a reduction-oxidation (redox) reaction in which atoms have their oxidation number (oxidation state) changed.
Reserve Capacity The capacity of a battery, measured in minutes, to keep a vehicle operating if the charging system fails.
Sealed Cell A cell where all reactants are retained within the container. May contain a vent for release during abusive overcharge.
Secondary Battery A backup or spare battery used to replace the primary battery when discharged.
Self-Discharge Is 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.
Separator Material which provides separation and electrical insulation between plates of opposite polarity.
Series Interconnecting cells or batteries by connecting the positive terminal of one unit to the negative terminal of the next, which doubles the battery voltage.
Wound Interior cell construction in which plates are coiled inside.

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