The Isolator Charge Solenoid is supposed to separate the chassis batteries from the house batteries when the motor is off, if it has an issues, I guess it could cause an issue with one or the other getting drained. I don't think this is an issue with my RV. My cheapo solar charger seems to be maintaining the chassis battery, and it has started without an issue the last few times.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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