VRLA battery uses sponge active materials on negative plate which has high active and rapid reaction with oxygen feature to absorbing oxygen reaction at negative plate against water loss. Thus VRLA battery doesn't need to refill water and equalizing charging.
●The charge/discharge reaction of the lead-acid battery can be expressed by the following equation
●Reaction from Beginning of Charge to Before the Final Stage
Charge reaction of standard lead-acid battery.
●Reaction after Final Stage of Charge
This phase is that charging cause electrolysis of water. Oxygen generated from positive plate reacts sponge lead of negative plate to keep discharging status, which can restrain hydrogen generation.
●Here is the reaction equation
Oxygen generated from positive plate rapidly reacts charging active materials of negative plate into water, completely prevents water loss.