Many home security systems will go offline but will work off a backup battery when the power is down. Some alarm systems operate using a 12 volt 4.8 AH Rechargeable Sealed Lead-Acid Battery. These run on a trickle charging system. Trickle charging allows a battery to self-charge at a low rate in order to remain fully charged. Lead-acid batteries last longer than a typical lithium-ion battery, which needs an adapter in order to recharge regularly.