A secondary battery is any accumulator that can be continuously charged/discharged.

Self - discharge

It is the battery capacity loss during storage or inactivity. It must be avoided or limited by practicing FIFO (first in – first out from store) and it is increased under high ambient temperatures storage.

Separator

A microporous PE or Composites (PP, Rubber, Glass Mat) foil that provides electrical insulation between the cell plates, preventing short-circuits and allowing a high ionic transference.

Service life

The battery performance measured in years or endurance cycles.

State of charge

The remaining capacity in a battery, in relation to the rated capacity.
It can be estimated by electrolyte density and open circuit voltage measurements .

Sulphation

When a battery remains unused for a long time and not in a fully charged state the lead sulphate in the plates recrystallizes forming a high resistance layer, sometimes causing short-circuits in the cell by penetrating the separator’s micropores and generally more or less reducing the recharge capabilities of the battery.