Needs to fire up the generator and charge things up. If his batteries are to low to fire up the generator he needs to hook up the power cable for lights/brakes to the truck and fire it up. That should give him enough power to get the generator running.
If he's using an inverter to take power from the 12v batteries he could be draining his batteries. Without knowing his battery setup it's hard to say, and not knowing how well he maintains the batteries or their age it's hard to give much advice.