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VRLA batteries

Technical Glossary



Product of current in amperes multiplied by the time current is flowing. Capacity of a cell or battery is usually expressed in ampere-hours. Abbreviated as Ah.


Electrode at which an oxidation reaction (loss of electrons) occurs. In secondary cells, either electrode may become the anode, depending upon direction of current flow. The negative electrode is the anode on discharge.

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One or more electrochemical cells electrically interconnected to form one unit and having provisions for external electrical connections.

Battery Case

Battery box or enclosure which contains cells, connectors, and associated hardware.

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Rated capacity of the cell or battery. Call charge/discharge current is often specified in terms of a multiple of C. (For example the 0.1C current for a cell rated at 1.4 Ah is 140mA.)

C Rate

Charge or discharge current in amperes that is numerically equal to the rated capacity of a cell in ampere-hours.


Amount of charge available from a battery or cell. Measured in ampere-hours. There are various sub definitions of capacity as listed below depending on the conditioned under which it is measured.

Actual Capacity

Cell capacity of a fully formed and fully charged cell when measured under non-standard conditions including non-standard end of discharge voltage.

Available Capacity

Capacity of a fully formed and fully charged cell delivered under non-standard conditions including non-standard end of discharge voltage.

Dischargeable Capacity

Capacity which a partially discharged cell can deliver before it becomes fully discharged or the amount of capacity that can be withdrawn after a limited charge input.

Nominal Capacity

Capacity typically delivered under standard conditions; a value greater than rated capacity which is a minimum value.

Permanent loss of Capacity

Reduction in cell capacity from the "fully formed, as new" value, measured under standard rating conditions, that is not recoverable by reconditioning.

Rated Capacity

Capacity value shown in the specification sheet. The minimum expected capacity when a new, but fully formed, cell is measured under standard conditions. The basis of the C rate. Note that rated capacities depend on the standard conditions used which may vary from battery to battery.

Residual Capacity

Capacity remaining after discharge.

Retained Capacity

Capacity remaining in a cell after an open circuit rest period. The result of self- discharge.

Standard Capacity

Cell capacity measured under standard conditions.

Temporary Loss of Capacity

Reduction in cell capacity that is recovered when the cell is reconditioned.


Electrochemical unit, composed of positive and negative electrodes, separator, and electrolyte, which is capable of storing electrical energy. When encased in a container and provided with electrical terminals, the cell is the basic "building block" of a battery. Although the capacity of the cell is determined by its size, the cell's voltage is strictly a function of the basic electrochemistry of the couple.

Cell Reversal

Reversing of polarity of terminals of a cell in a multi-cell battery due to over discharging.


Return of electrical energy to a battery.

Charge Acceptance

Willingness of a battery or cell to accept change. May be affected by cell temperature, charge rate and state of charge.

Charge Efficiency

Value obtained when the increase in dischargeable capacity of the battery is divided by the current input. A measure of charge acceptance. Also indicates

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