I have a 2011 Provan Tiger, with two AGM (I think) 6V golf cart batteries to power the needs of the coach. Battery health is monitoring by a wall mounted digital readout that shows charging levels and output. I also have a 125W solar panel on the roof, with its own separate monitor panel also showing battery charge/output levels.
I never had any problem keeping the batteries charged while driving or while plugged in at a park with shore power, but while boondocking, they ran down after about three days due mostly to the use of a compressor fridge. The single solar panel wasn’t enough to keep them charged up while they were being used while dry camping, and running the propane generator for a few hours didn’t fully charge them back up either.
As a point of reference, we have 440ah of Lifeline AGM batteries and can charge from the alternator at 200 amps continuous (until it starts to taper due to battery acceptance) or from a 100 amp Magnum shore charger. To get to true full, where the batteries are only accepting .5%C (2.2 amps) from under 50% SOC takes a minimum of 8-10 hours on charge.
The manufacturer told me that the generator wasn’t actually the best way to fully recharge the batteries, unless I ran it for many hours, because the power from the generator runs through the 12V converter and that slows down the charging rate.
Supposedly, the system is set up this way to protect your coach batteries from being overcharged while staying hooked up in a park and leaving your rig plugged into the shore power.
So the solution suggested to me was to figure out how directly hook up a portable, quick charge battery charger directly to the coach batteries, and then run that charger while it’s plugged into a wall outlet in the rig with the propane generator running.
Basically, by doing it this way, the time to charge the batteries would be about half the time or less than it would take to charge the batteries just running the genny and powering the charge through that slow converter. It’s the same concept essentially as plugging a battery charger in in your garage and hooking it up to your car battery when your car battery needs a boost.
I hope that helps explain things a bit better.