Rex:
When I bought my Contessa, it came with low chassis batteries. I was unable to be plugged in every night over the first week of ownership (traveling and waiting to get across the border) so the chassis batteries failed completely and I replaced them. Then I had to leave the coach unplugged for another 3 weeks, and the chassis batteries were totally discharged again. Talk about a steep learning curve. I got going, then determined that the charging of the start batteries, from shore power, was not happening at all, and there was a continuous draw from the CAT ECM of about 2 amps. SO now I know why the batteries were discharged, and why they were staying that way. I put a small charger on them, dedicated to just the Chassis batteries, but it failed within a year. I then put a relay type isolator/charger (sometimes called a BIRD system) that takes power from the house batteries when they have enough of a charge and charges the chassis batteries. Since doing that, no further problems with charging. I also put a positive shut off, a knife switch, on the negative terminal of the chassis batteries, so that when there is no charging power, there can also be no load whatsoever. Again, no further problems.