Class C Battery issues

[ginaseven]

Guidance needed....
I just came home from my 3rd trip with my new to me 2013 Coachman Leprechaun Class C.
The first trip all went well until I was packing up to leave and could not get the slides to retract. After checking everything I could think of, I realized that the main battery disconnect was turned to Off. Turned it on and slides came in without an issue. I took the coach battery to NAPA when I got home bc it did not have a charge, and would not charge. They charged it and tested it and said it was fine.
Trip 2...Initially the water heater would not come on in gas or electric, after a few seconds the DSI fault light came on. I tried it a few times a day and on day 3 it came on in the Electric mode.
Trip 3...The water heater never came on in either mode. After camping for 5 days, getting ready to pull out and the RV won't start, the motor battery is dead. I got a jump and it started right up. I figured I inadvertently left something on that drained the battery. (new battery in 2019)
I drove about 2 hrs to a Flying J to dump. I turned the RV off (sure that 2 hours was enough to charge the battery) This took about 15 mins, when I went to leave and of course it would not start again.
Where should I start? Replace the House battery? The motor battery? None of the above 🙂
Thanks as always for your expertise!!

[theoldwizard1]

MEXICOWANDERER wrote:
A bi-directional smart solenoid reduces these problems by a factor of 99%

I do NOT disagree, but a DC-DC battery charger instead takes it to 100% !

[MEXICOWANDERER]

A bi-directional smart solenoid reduces these problems by a factor of 99%

[BFL13]

On shore power you appear to be getting your 12v for the house from the engine battery. Previous owner did something there I think. (Perhaps because the converter was not doing it for him and he didn't fix that.)

You don't need new batteries, just need to solve the battery charging mysteries.

Leave the WH till later, since it might be just a 12v problem to do with the first issue.

Some Class Cs have a three-position dash switch for getting engine starting power from the house batteries, while others don't and just have engine and house batts in parallel whenever the ignition is on ("running circuit") What do you have? This may be what has been altered.

[theoldwizard1]

Take your engine battery to NAPA have it charged and tested, in that order.

Replace you house battery disconnect with a DC-DC battery charger. Not cheap, but it is 100% automatic and you can be sure that it will charge while driving. Also you need to verify that your converter is output sufficient voltage to keep the house battery charged. You should have about 13.4V at the house battery when plugged in. If not, there are a lot things to check.

Water heaters are tricky. There are multiple safety features that will prevent it from starting. Each needs to be tested.