A battery support unit, such as a defibrillator battery charger, tests a battery having a memory for an error condition. If the battery support unit finds an error condition with the battery, it transmits error data to a mailbox located in the battery's memory. Other battery support units or electronic devices, or even this battery support unit at a later date, can read the error data in the mailbox and take an appropriate action. For example, the battery support unit can read the mailbox and, if it finds error data placed there by itself, another battery support unit, or an electronic device, enable an indicator, such as an indicator that informs a user that maintenance needs to be performed on the battery. When battery maintenance has been selected, the battery support unit reconditions the battery by charging and discharging the battery a predetermined number of times, and also performs additional testing on the battery.