We have a 2015 Tiffin Allegro Open Road. We don't store it for long periods of time but we seem to drain the coach batteties after about 10 days to 2 weeks even though we turn off the 12v switch at the entry steps. We have access to 120 ac power in the storage unit. Is there a problem leaving the unit plugged in to the 120v power while stored in order to avoid draining the batteries?