We recently added a heavy duty set of battery cables from our tow vehicle to the rear bumper and added similar cables from the trailer batteries to the trailer hitch. Now we can charge our trailer batteries as we drive. Also added large cables in the engine compartment so we can charge the batteries from the front of the truck. Works very well so far. Considering adding a DC-DC converter so the trailer batteries are charged with a multi-stage charging profile. Here's a link to the separate thread on the upgrade. And a few pictures showing the charging system works from the front of the vehicle and while we're towing.
Lucius and Danielle
1992 29' Excella Classic / 2010 Interstate
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...