Did you lose power before you received the call? If so, how long was the power out? In most cases the battery should maintain the system for 2-4 hours if a Lynx wireless system. If a Napco system, typically a battery will last 18-24 hours. If the power was out for a longer period of time, the battery should automatically recharge. If the battery does not recharge properly, you will be notified again in 24 hours. If you did not lose power or the power was off only a short period, the battery should be replaced.