User led 3 stays on

I have two BBBs, in each I put a battery. When I switch them off, in one the leds go out, in the other the user led 3 (the one closest to the network connetion) stays on, and the board drains the battery in a day or so. I’m not aware of changes I made to the boards, other than disabling dns on ssh and updating debian. What can be the difference, or what can I do to switch the one board completely off?