Tow vehicle charging RV batteries

If you aren’t pulling, you aren’t charging regardless of modifications. Solar with a generator backup.

Thats not to say that it is useless . A good 6 or 8 hour drive will bring my batts back up . Sitting at idle waiting for a battery to recharge , ya better bring your lunch !

Thats not to say that it is useless . A good 6 or 8 hour drive will bring my batts back up . Sitting at idle waiting for a battery to recharge , ya better bring your lunch !

Some have used a DC to DC converter in the trailer charge line to increase the voltage high enough so that charging is better. If you do, be sure to include a way to power the trailer breakaway switch - DC to DC converters are one way devices...

Smart Boondockers use solar and backup with a generator.

It is pretty much a trickle charge, if the vehicle is set up to do it. Alternators are usually sized to supply the demand the vehicle will be needing. You would have to have a much larger amperage alternator or install a second alternator if you have room for it in order to put a dent in charging the house batteries.

The problem is mostly that it's a long way from the alternator to the batteries and the vehicle manufacturers use wire that is too small for this circuit. It's often something like #14 or so. It really needs to be more like #6 or larger to get good current flow. People who really want to set things up well for this will run a heavy charge line from the battery tot he rear of the tow vehicle with something like #2 welding cable. Then, you use connectors meant for a lift gate trailer or perhaps some Anderson Powerpole style connectors rated for 100A. Of course this require the matching connector and more #2 cable on the trailer to the batteries.
The other problem is that in the ever present race to improve vehicle MPG many modern vehicles actually lower the alternator's output voltage when the vehicle is just "cruising down the road". Usually turning on the headlights or putting the transmission into tow/haul mode will raise the charge voltage back up.