Rob,
I have been charging my 2 Group 24 batteries on my TT when dry camping at state parks for a couple years now by hooking up jumper cables from my truck to the batteries. I just let the engine idle for an hour or two and they get maybe 30 Amp Hours pushed into them. I can go about 3 or 4 days before I need to do this because I use all LED lighting (cheap from ebay).
As far as your idea of charging your PUP battery from your Truck "House" Battery ("House Battery" gets charged while driving Truck), you can use a cheap 12V DC/DC converter to fully charge your PUP battery from your house battery. Check out this thread that describes an $11 dc/dc converter (10 AMP max).
10 Amp DC/DC converter for trailer battery chargingI rigged mine up recently and it works. You can adjust the output voltage to 14 Volts for the PUP battery, and the converter will just increase the current draw from your House Battery as it's voltage drops. Hook it up and let it sit for 4 hours and you will have transferred up to 40 Amp Hours to your PUP battery. Assuming the House Battery on your truck can last that long and your PUP battery could accept that many Amp Hours.
Now you end up with a charged PUP battery and a discharged Truck House battery that will charge up from driving around.
Ed
Ed
