I tried this with a mutli-meter. It does not charge the battery in this mode.That is service mode. Just lets them power the vehicle on and run diagnostics. I guess it is sort of an accessory mode since you can operate the accessories and not drive, not sure if there is any harm in leaving it in that mode for a long time. I don't know if the car will charge the 12v battery in this mode or if it only runs off the 12v battery in that mode. I suspect it would not charge the 12v battery though but I don't see anything in the manual that states one way or the other.