VRLA and Sealed Maintenance Free batteries


Tomy Zacharia

Dear Burman,
No difference. A lead acid battery cannot be sealed (say helium tight), so a valve is used to maintain positive pressure inside the battery
to allow for recombination of hydrogen and oxygen into water. The utility of the valve is to save the battery from an explosion in the case of a short circuit (causing a large amount of hydrogen gas to evolve) or any other event such as overheating of electrolyte.

The battery is maintenance free in the sense that distilled water/battery acid (electrolyte) is not required/cannot be added.

Tomy Zacharia