The override timer is a software timer which starts at the beginning of each charge and runs until the green ready light turns on. There is a fixed maximum time allowed for each charge, typically 18 hours. Should the time exceed that amount, the charger enters “fault mode”, indicated by a flashing green ready light. The purpose of this is to prevent overcharging due to fault conditions such as a shorted battery cell. Fault mode can be cleared either by switching the AC power supply on and off, or disconnecting the battery.