Re: battery charger
glennis, I answered you via private message, but I'll repeat it here so others can comment!
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I'm not aware of the MH that you have, but most MHs have an AC to DC converter to supply the MH with 12VDC as a substitute when you plug into AC at a site. In conjunction with that converter, they usually provide a simple battery charger to charge your batteries up. If you always run on AC, then you wouldn't really even need the batteries. (As a matter of fact, some batteries are charged so much the water is dried out.)
If you have such a converter (not inverter), then there probably is wiring to your battery terminals or some junction for charging purposes.
The vehicle alternator can be wired (through an isolator) to the MH batteries for recharging that way also. My MH does it all of these ways.
Now, where I use the VDC is while my MH is stored between trips. I have a switch that cuts out the other charging systems, then I connect the portable VDC. The advantage here is that it won't dry up the battery during long-term charging, and it has the desulfating effect (which works) on them to make them last longer. It isn't a fast charging system, but I think it is the best.