About to purchase preowned Lance 1161 questions, new to TC's

Most people do not have success with using the standard 7 pin plug in to keep the TC battery charged. The hot wire on most original 7 pin plugs is too small.

Many Lance users, including myself, wire a new 6 pin Lance plug into the bed and come directly off the truck charging system with much larger wiring such as a #6 gauge or larger. Both positive and negative wires.

Try what you have and see if you need to make a change later or not.