I had 2 Walmart group 29s. One was 7 years old. I replaced with a single group 27 from Autozone. Yes, I put it on my charger for 6 hours before installing it.
The breaker I'm talking about is a 12V auto reset - I've never looked at the rating. The cable from the battery goes to the cutoff then to the autoreset breaker then to 12V distribution. There are several auto reset breakers for things that don't run through the fuse panel - like the front jacks and slideout controllers.
I know a Group 27 isn't much battery but it was a stopgap measure until I decided what I really want. It shouldn't go flat on furnace only in 20 minutes - it should run for hours.
I'm thinking the autoreset breaker needs to be replaced or the cutoff.
BTW, checked the 12V cables into the fase panel and they're tight. Next will check the battery and then the buried converter if I find nothing at the battery.
