It depends on what kind of battery isolation manager (BIM) you have. In recent years Thor has been installing Precision Circuits BIM 160 or 225 which charges both ways. Older systems, those often referred to as "BIRD, Trombetta" don't go both ways and need something like the Trik L Start to charge the chassis batteries.
But in any case your chassis battery shouldn't have dropped that much in a week. Look for a continuing load powered by the chassis battery like an interior light that may have pulled it down.
You should be able to use your Aux Start switch to get the chassis engine going even if the battery is near flat.
David
David
David
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