Hey dhenry, I think removing power from the arduino entirely is necessary, since even a (very) small current would in time drain the battery beyond the safe charge voltage, and I don't want that to happen. When the power is removed from the arduino, the leds go out too, but that's fine. Would you know what causes the voltage to drop on an output that is not switched by the code? I can imagine that that could happen when too much current is drawn, but that's not the case here.