Funny you should bring this up. Two days ago I tried to start up our rig. Nothing. No cranking noise, nothing. So I used the coach battery emergency assist and it started up.
The coach had been sitting for three weeks, not unusual for us. It has been idle for a month and started right up. Voltage was 9.3V Thursday a.m.
Shore power was coming in for the three weeks and coach batteries were being charged. The only thing I noticed was that the propane alarm goes off when charging, sometimes, and it had been beeping overnight for about 10 hours, +/-.
Not likely that the propane alarm is wired to the chassis battery but I do not have a wiring diagram to check it out. Not likely.
More likely the battery had a dead cell. There was a new battery installed yesterday and I think I will check the voltage each day to see if the drop is "normal" or excessive.
I might switch the house batteries OFF and check the chassis battery, also.
The old AC Delco battery did not have caps to check the fluid, I don't think. I was in a hurry to go to the dealer for another two items and did not check.
2003 Dolphin LX 6355 w/ W22 chassis; 8.1L gasser & Allison 1000