Have 2017 Thor ACE, battery dead, jumped started and let run for about an hour. Unplugged from 30amp electrical while in RV barn. Few days later went out to Thor and discovered house batteries are dea...
Since your talking about the chassis battery, A 2017 motorhome was likely sold in 2016 or at least the battery was placed then. So it's likely nearing the end of it's life. Any auto parts store can test and recommend a suitable replacement.