12 Volt Battery Discharge Fix

12 Volt Battery Discharge

Does anybody find it necessary to keep a battery maintainer on the 12 volt accessory battery if the Prius sits more than a couple of days? Both batteries in my 01 and 05 Prii tend to drain if I don't maintain them. I't seems like I've read here before that the OEM 12v batteries are prone to discharging if the car is not driven enough. Is this the case or is there a need to track a source of drain on the battery?