I had the same problem with my batteries. Talked to an O'Riley's owner who also had a motorhome and his suggestion was to use a solar panel to keep them charged.
I did the following. Located the solar panel flat on the dash at the center of the windshield. Made sure the batteries were at full charge. Used small jumper cable and hooked up the chassis and the coach batteries in parallel so the charger would keep all three batteries topped off. The panel does not produce enough juice to "charge" but does produce enough to keep them topped off.
I did not use any cut offs. I have checked the status of the batteries about once a month by using a volt/ohm meter and making sure the voltage was maintained at least at 12 VDC. Cranked each time and all batteries were at full charge.
Now I only check about every 2-3 months and all has been fine.
When I get ready to drive, I just remove the jumper cables, unplug the solar panel and roll up the wires. Such a relief!
Chuck
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