Some 747-400's have a Towing Bus. This is powered by the battery. This can power essential items for towing, such as nav lights (not red beacons or white strobes). This can be used when APU or tug power is not available for a tow.
I don't think many people seem to know how to activate it though. It involves selecting the battery ON, Standby Power OFF and a Towing Bus switch on the overhead panel ON.