Thank you, Larrgh. On the bulletin, it mentions a relocation of the water pump. Does that apply to this dual installation?
I didn't post that they were discharging while I drive; I posted that the truck does a poor job of charging while I drive. There are lots of reasons why someone pulls out with low charged batteries in their RV's. It would be nice to have a little more charge going into them than currently being provided. The OEM alternator is rated at 200 amps, and if I'm understanding correctly, the truck and it's systems uses most of that. Add the trailer system, and there's not much left.The better question is why are your batteries discharging while you drive? If you have a DC switchable fridge the dual alternators won't help much. Everything else should be off. As an aside running propane for the fridge while driving is a bad idea. A) the obvious danger in an accident. B) the flame will heat stress the vent stack when you are out of level.
So, that goes back to my original post about needing the field coil being fed from the batteries in the camper. On a self-exciting alternator, you would simply run the output of the alternator to the batteries using an appropriately sized cable - probably 1-0 or 2-0. The field terminal would be attached to that cable. On your fancy new alternators with the "better idea by Ford" technology, the alternator is regulated by the PCM. I have no idea how you would control it. I would suggest - if you insist on going that route - of getting an alternator shop to build you a self-exciting alternator that fits into the case size of the second alternator. For example, if the alternator is a Ford 3G case, just call one of the shops and tell them what you want to do and need an appropriate alternator in that case size. Then, it won't be PCM driven - it will only be driven by the voltage of the batteries you want to charge.Question: how would you regulate the charge from the second alternator to the rv batteries? Or are these newer alternators self-regulated to kick on and off depending on demand for charge?