For the coach batteries just make sure they are 100% virgin lead. Menards batteries sell at a great price. Costco, Sams club also good. Batteries have a sticker with the date they were made so look before you buy. It is not uncommon to find a battery a year old or more on a shelf. Kind of like picking out Milk find the newest one. I was at a autozone once and the only deep cycle they had was almost 2 years old.
I wonder if the chassis came from Ford with a battery. The batteries Thor installs in the coachs are garbage and most need to be replaced within a year. Mine didn't even last that long. Now the batteries from Ford are good batteries and you shouldn't have a issue but I'm not sure if the chassis came with a battery or Thor put in a garbage one.
A loose or corroded connection can cause the coach battery to drain.
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