By adding the electrolite in the cell.
Means if it is a Lead Acid battery, Add Diluted Sulphuric
Acid(H2SO4) in the electrolyte.
If it is a Nickel Cadmium battery, Add Potassium Hydroxide
(KOH) in the electrolyte.
By adding distilled water, electrolyte becomes more thin
and its specific gravity will go less.
When the specific Gravity will becomes less?- because of
charger is failure,and poor electrolight sulution.If it is
level of solution is ok,Then cahrging is necessary,need not
wants to add dilute sulpueic acid/distiilled water.If it is
level is less or spefic gravity is beyond limit ,necessary
to add distilled water.
As my knowledge should not add dilut selphuric scid in
Battery,Only topping up distilled water is enough.
If it if dead battery -if 1.25 specific gravity solution
adding,can you use for on load as like a normal battery?