Absorbed Glass Mat (AGM)- A highly porous fiberglass mat separator which functions as an electrolyte retainer, somewhat like a sponge. Usually found in premium, specialized batteries like valve regulated lead-acid (VRLA) battery types. This technology provides the highest oxygen recombination efficiency and improves the high-rate discharge performance.
Ampere (AMP)- The unit of measure of current flow through a conductor or circuit.
Capacity- The ability of a fully charged battery to deliver a specified quantity of electricity at a given rate (Amperes) over a definite period of time. Battery capacity depends on construction, materials used, size, weight, discharge rate, temperature, resistance and age.
Circuit- An electric circuit is the path of an electric current. A closed circuit has a complete path. An open circuit has a broken or disconnected path.
Circuit (Series)- A circuit which has only one path for the current to flow. Batteries arranged in series are connected with the negative of the first to positive of the second; negative of the second to positive of the third, etc. If two twelve volt batteries are connected in series, the circuit voltage is equal to the sum of both batteries or twenty-four volts.
Circuit (Parallel)- A circuit which provides more than one path for current flow. A parallel arrangement of batteries would have all positive terminals connected to another conductor.
Corrosion- An accumulation of solid sulfates of iron copper or other metals, usually in the terminal area, contributing to poor electrical contact between cables and battery terminals.
Cold Cranking Rating- The number of amperes a battery at 0 degrees F can deliver for 30 seconds and maintain a battery voltage of 1.2 volts per cell or higher.
Cranking Rating- The number of amperes a battery at 32 degrees F can deliver for 30 seconds and maintain a voltage of 1.2 volts per cell or higher.
Current- The rate of flow of electricity. The movement of electrons along a conductor. It is comparable to the flow of a stream of water.
Current (Alternating)- A current that varies periodically in magnitude and direction.
Current (Direct)- An electrical current flowing in one direction only. A battery delivers direct current (D.C.) and must be recharged with direct current.
Cycle- In a battery, a discharge and a recharge is a cycle.
Discharging- When a battery is delivering power, it is said to be discharging.
Electrolyte- This is a mixture of water and sulfuric acid that fills a lead-acid battery and allows the storage of electrical power.
Element- In a battery, a set of positive and negative plates assembled with separators.
Grid- A lead alloy framework which holds the active material of a battery plate and conducts the current.
Ground- In automotive use, the result of attaching one battery cable to the body or frame which is used as a path for completing a circuit.
Hydrometer- A float-type instrument used to determine the state of charge of a battery by measuring the specific gravity of the electrolyte (I.E. the amount of sulfuric acid in the electrolyte).
Digital voltmeter- An instrument that measures the open circuit voltage of a sealed battery.
Load Tester- An instrument which measures the battery voltage with an electrical load on the battery to determine its overall condition and its ability to perform under actual engines starting conditions.
Open Circuit Voltage- The voltage of a battery with no load. It is 2.1 volts per cell for conventional battery. The OCV directly corresponds to the state of charge in a battery.
Reserve Capacity Rating- The power available to run electrical accessories if the alternator fails. It indicates the number of minutes a fully charged battery at 80 degrees F can be discharged at 25 AMPS and not fall below 1.75 volts per cell.
Resistance- The opposition offered by a substance to the free flow of an electric current.
Short Circuit- A shortening of an electrical path within a battery cell which results in a reduction of cell voltage under load.
Specific Gravity-The strength or percentage of sulfuric acid in the electrolyte solution.
State of Charge- The amount of electrical power stored in a battery at a given time. State of charge is determined by the amount of sulfuric acid remaining in the electrolyte (Specific gravity).
Volt- The unit of measure for electrical pressure.
Valve Regulated Lead Acid (VRLA)- A sealed lead-acid battery cell incorporating the use of an internal pressure release valve designed to maintain internal cell pressure. As internal battery or cell pressure reaches and surpasses the valve design limits, the valve will, by design, release momentarily and reseal. These batteries are available in Gel and AGM battery types.
