You've got an alternator in your big engine, why not use it to charge all your batteries? If I just didn't buy an 2 bank onboard charger for the Lund, I would have done a setup similar to a buddy of mine just did. Also if you have a 7 pin trailer harness, you'll charge everything while driving as well. Seems like the best solution out there. Maybe Dave will come in here and explain it a bit better then I did, lol.