Definitions

Absorbed Electrolyte

The electrolyte in a battery is absorbed in an Absorbent Glass Mat between the plates to ensure that there is no free liquid electrolyte to spill or leak from the cell. The battery using this technology is typically referred to as an AGM battery.

Absorbent Glass Mat

A blotter-type separator used between the plates in an AGM battery. The absorbent glass mat separator absorbs all the free liquid electrolyte, thus immobilizing the electrolyte.

Capacity

The quantity of electrical energy measured in watt-hours or ampere-hours produced by a battery during discharge.

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.

Trickle Charge

A very low rate constant current charge to maintain a battery at a full state of charge.

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.

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 hot environment with either little ventilation or shorted cells. See Float Charge.

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.

hort Circuit

An unintended conductive path between poles of different polarity. When a short circuit exists within a cell, its open circuit voltage will eventually decline to zero.

SLI

The acronym for a 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.

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.

Reserve Capacity

A measurement of the minutes a battery can supply 25 amperes to an end point voltage of 1.75 volts per cell. This rating is used with automotive (SLI) and marine batteries.

Rated Capacity

The ampere-hours or watt-hours a battery delivers under standard conditions at a specified discharge rate to a specified end point voltage. See Standard Conditions and Standard Discharge Rate.

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.

Internal Resistance

Expressed in ohms, the total DC resistance to the flow of current through the internal components (grids, active materials, separators, electrolyte, straps, intercell welds and terminals) of the battery.

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.

Grid

The lead alloy frame to which active materials are pasted. The grid provides the conductive path for the electron current during charging and discharging of the battery. The assembly of the grid and pasted active materials form the plate of the battery.

Load Tester

Hand-held resistive device used to place a test current on the battery while the resulting battery terminal voltage drop is monitored.

Float Charge

Placing a battery on continuous charge at a recommended voltage to maintain the battery at a full state of power while minimizing overcharge.

Deep Cycle

A battery discharge consuming more than 80% of the battery’s rated capacity. Deep cycling typically occurs in motive power and “off grid” systems.

Constant Current (CC)

An electron flow through a conductor (a current) that does not vary significantly from a pre-set value. During discharge, a constant current drain can be maintained by reducing the resistive load as the battery voltage normally declines. To recharge a battery at a constant current level, the charging voltage must increase as the battery cell voltages increase.

Constant Voltage (CV)

A voltage that does not vary significantly from a preset value. When recharging a battery at constant voltage, the current acceptance will decline as the battery cell voltage rises. The battery cannot be discharged at a constant voltage. The battery voltage normally declines during the discharge.

Constant Power (CP)

DC power in watts is equal to the product of voltage multiplied by current in amperes. A constant power discharge occurs when the load current is increased during the discharge by an amount proportional to the normal decline in battery voltage.