Stands for Absorbed Glass Mat. This is the separator system used in all Lifeline® AGM batteries.


Active Material

Electrode material which produces electricity during its chemical conversion. In the positive plate it is lead dioxide. In the negative plate, it is sponge lead.



Unit of electrical current abbreviated as amps or A. Amps = Watts/Volts or A = W/V.


Ampere Hour (Ah)

The capacity of a storage battery is measured in ampere hours. One ampere hour is defined as a current flow of one ampere for a period of one hour. Five ampere hours means a current flow of one ampere for five hours, a current flow of 2 1/2 ampere for 2 hours, or any multiple of current and time that will result in five. This relationship can be expressed as follows: Capacity (Ampere hours)= I*T, where I is the current (in amperes) and T is the time (in hours). The capacity of a storage battery is based on a given discharge rate, since the capacity will vary with the rate of discharge.


Boost Charge

A charge applied to a battery which is already near a state of full charge, usually of short duration.



The quantity of electricity delivered by a battery under specified conditions, usually expressed in ampere hours.


Capacity, Rated

A designation by the battery manufacturer which defines the performance of a new battery at a defined rate of discharge. For Lifeline® AGM batteries, the rated capacity is based on the 20 hour rate.


Capacity, Residual

Capacity remaining at particular point in time and set of operating conditions, usually at a partial state of charge condition.


Cell Reversal

Reversing of polarity within a cell in a multi cell battery due to over discharge.



The conversion of electrical energy from an external source, into chemical energy within a cell or battery.


Charge Rate

The rate at which current is applied to a cell or battery to restore its capacity.


Charge Retention

The ability of a charged cell or battery to resist self discharge.


Charge, State of

Ratio of the amount of capacity remaining in a battery to the capacity when fully charged. A battery at 25% state of charge has 25% capacity remaining versus what it could give if fully charged.



Device capable of supplying electrical energy to charge a battery.



The process of converting electrical energy to stored chemical energy. The opposite of discharging.


Charging Efficiency

Ratio of the Ampere hours delivered on discharge to the Ampere hours needed to fully charge a battery.



A special constant current charge process used to restore a battery’s capacity after extended storage periods or deep discharge exposure. Also known as reconditioning.


Constant Current (CC) Charge

Charging technique where the output current of the charge source is held constant. Warning! This procedure may damage the battery if performed on a repetitive basis.


Constant Voltage (CV) Charge

Charging technique where the output voltage of the charge source is held constant and the current is limited only by the resistance of the battery and / or the capacity of the charge source. Also known as Constant Potential (CP) charge.



The rate of flow of electricity. The movement of electrons along a conductor. It is comparable to the flow of a stream of water. The unit of measurement is an ampere.


Cut Off Voltage

Battery voltage reached at the termination of a discharge. Also known as end point voltage or EPV.



One sequence of discharge and charge.


Cycle Life

The total number of charge/discharge cycles before the battery reaches end of life (generally 80% of rated capacity).


Deep Discharge

Withdrawal of more than 80% of the rated capacity.


Depth Of Discharge

The portion of the capacity taken out during a discharge, expressed as a percent of rated capacity.



The conversion of the chemical energy of a cell or battery into electrical energy and withdrawal of the electrical energy into a load.


End Of Life

The stage at which the battery fails to deliver acceptable capacity (typically 80% of nameplate rating).


Float charge

A method of maintaining a battery in a charged condition by continuous, long term, constant voltage charging at level sufficient to balance self-discharge.



The evolution of gas from one or more of the electrode plates in a cell. Gassing commonly results from local action (self discharge) or from the electrolysis of water in the electrolyte during charging.


Internal Impedance

Same as Internal Resistance.


Internal Resistance

The opposition or resistance to the flow of a direct electric current within a cell or battery; the sum of the ionic and electronic resistance of the cell components. Its value varies with the current, state of charge, temperature, and age. With an extremely heavy load, such as an engine starter, the cell voltage may drop significantly. This voltage drop is due to the internal resistance of the cell. A cell that is partly discharged has a higher internal resistance than a fully charged cell, hence it will have a greater voltage drop under the same load. This change in internal resistance is due to the accumulation of lead sulfate in the plates.


Open Circuit Voltage

The voltage of a battery when it is not delivering or receiving power, and has been at rest long enough to reach a steady state (normally, at least 4 hours).



The forcing of current through a cell after all the active material has been converted to the charged state. In other words, charging continued after 100% state of charge is achieved. The result will be the decomposition of water in the electrolyte into hydrogen and oxygen gas, heat generation, and corrosion of the positive electrode.


Self Discharge

The decrease in the state of charge of a cell or a battery, over a period of time, due to internal electrochemical losses.


Series Connection

Voltage of the system is cumulative. Capacity stays the same.


Shelf Life

The period of time (measured from date of manufacture) at a specified storage temperature after which the cell or battery needs to be boost charged so it does not suffer permanent capacity loss.


State Of Charge (SOC)

The available ampere hours in a battery at any given time relative to its full charge capacity.


State Of Health (SOH)

The available ampere hours in a battery when fully charged relative to its rated capacity.



Refers to the formation of hard lead sulfate crystals in the plates that are difficult, if not impossible, to reconvert to active material.


Temperature, Ambient

The average temperature of the battery’s surroundings.


Temperature, Cell

The average temperature of the battery’s internal components.


Trickle Charging

Method of charging in which the battery is either continuously or intermittently connected to a constant current charging source to maintain the battery in a fully charged condition. Not recommended for use with Lifeline® AGM batteries.


Vent Valve

A normally closed check valve located in a cell which allows the controlled escape of gases when the internal pressure exceeds its rated value.



A release of gas either controlled (through a vent) or accidental from a battery cell.