VRLA (Valve Regulated Lead Acid) batteries are sealed, and therefore are maintenance free. While Gel and AGM (Absorbed Glass Mat) are two types of VRLA batteries, our focus is on the AGM. In these batteries the electrolyte is absorbed into a glass-fibre mat between the plates by capillary action. Victron VRLA batteries can be stored during long periods of time without recharge. The rate of self-discharge is less than 2% per month at 20°C. VIctron VRLA batteries have exceptional Deep Discharge Recovery as well.