Acid
Refers to sulphuric acid (H2SO4), the active component of the electrolyte, or a mixture of sulphuric acid and water.
Active Material
The porous structure of lead compounds that produce and store electrical energy within a lead-acid battery. The active material in the positive plates is lead dioxide and that in the negative is metallic sponge lead. When an electrical circuit is created, these materials react with sulfuric acid during charging and discharging according to the following chemical reaction: PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O.
AGM (Absorbed Glass Mat)
A type of non-woven separator material comprised almost entirely of glass microfibers that absorbs and retains the electrolyte leaving no free electrolyte in the cell to spill. VRLA batteries made with this material are often referred to as “AGM” batteries.
Alloy
As used in battery practice, a homogeneous combination of lead and antimony.
Alternating Current
Electric current which does not flow in one direction only, like direct current, but rapidly reverses its direction or “alternates” in polarity so that it will not charge a battery.
Ampere (Amp, A)
The unit of measure of the electron flow rate, or current, through a circuit.
Ampere-Hour (Amp-Hr, Ah)
A unit of measure for a battery’s electrical storage capacity, obtained by multiplying the current in amperes by the time in hours of discharge. (Example: A battery that delivers 5 amperes for 20 hours delivers 5 amperes X 20 hours = 100 Amp-Hr of capacity).