Important: it stops charging when the battery is charged, and the red LED turns green. Simple, but it seems to be missing on other consumer devices.
Charging systems are separated, so it can charge a battery at a time, and although the two together are loading, each has its own circuit. No unnecessary wear so.
To see if it is reliable over time, but for now, I love.
Fast charge, about 3 hours for the big pile 9v 300mAh (I bought too).
