They do not. Infact you have it backwards, having it plugged in is letting it use it's full power rather than half or even less than half by running on battery power. If your laptop has a stealth mode then that is equivelant to running it on battery power. I have to keep my laptop plugged in or else I get about an hour at most of power and it's weak so meh. Plugged in though this baby is a power house.