Basically, Valve Regulated Lead Acid Battery or VRLA is one of the many types of the basic Lead Acid batteries. The other name of the VRLA batteries is Maintenance Free or MF batteries. This name is due to the fact that VRLA batteries do not need regular checking. Checking of the electrolyte level of the lead acid batteries is one of the few basic operations with which any new driver is introduced. Valve Regulated Lead Acid Batteries – VRLA does not need this check because hydrogen and oxygen in the cells are producing water which remains in the VRLA battery.
The term Maintenance Free or MF batteries needs to be understood with a caution. Some of the electrolyte can be lost and the VRLA battery can dry out and lose power. To prevent this, regular check need to be done by measuring conductance, impedance and internal resistance. In the case of irregularity of those values, a maintenance procedure known as rehydration is needed, because in this case there are some dry out of the VRLA battery.
VRLA batteries are popular with motorcycles because they can not leak and are more resistant to the higher levels of vibrations than regular Lead Acid batteries.