The Powerline 8 charges AAA and AA rechargeable batteries in any position and either size at the same time. State of charge of the inserted battery is not important when using this unit and it is suitable for all brands of AA/AAA rechargeable (NiMH/NiCd). Once a battery is fully charged, the charging process automatically stops and switches to trickle charge (with current pulses) to ensure the best performance and halt any battery self-discharge. Bright LEDs show the progress of each slot - RED for charging, GREEN for fully charged, flashing RED for fault. A USB outlet port is included for charging accessories such as mobile phones, tablets, etc.