I'm on my 3rd chassis battery, Odometer indicating 54000+ miles. The original gave up the ghost a long time ago but under warranty. The second one gave up the ghost just before we left for our current road trip but it's been working on it for quite some time. The "only" thing that kept it half way functional was with the routine use of a battery minder. The battery itself was defective and I got a new 7Yr-78 Delco battery. So far so good and the battery minder is always plugged in.
MikeT showed me the way he connected his and I adopted it. Connected in the front of the coach at the right side outlet, anytime the MH is plugged into shore power the BM is charging the automotive battery.
Instead of my dealer giving me an 18 ton hydraulic jack, huge rubber wheel chocks (2) and a host of other stuff which I will never use, they might have given me a BM and saved a bit of money.
The dealer should have been the one to hook you up with a BM. I obtained my BM for free from Camping World by attending a C2C seminar.