This charger allows to unload the old evil charged batteries then load them properly. It can charge each battery separately and not as 2 by 2 other chargers. In discharging phase (by pressing a button under the white cover), the central light is red. When the discharge is completed, the process moves handled automatically. During charging, an amber light lets you know which battery is charging. When charging is complete, the orange light goes out. Attention to heat batteries once charging is complete.