When we had our Avalanche set up for towing, the guy doing the work ran a fused 12v hotline from the umbilical cord's 12v line to the Avalanche's battery. In our setup, there was a completely new set of wiring and lights (tail, brake, and turn signals) installed for towing. What I don't know is if the hotline to the Avalanche's battery is regulated or needs to be regulated depending upon the state of charge of the battery. My concern has been that a long day or several days in a row of driving may burn up the Avalanche's battery.