We store our Boat all summer long and our Motorhome all winter long in Florida.
We place a few Sunpac hanging bags in each unit, just before we close it up.
We have been doing this for years and are very satisfied with the results. No mold in the closed up MH, during its winter nap and just a bit in the more drafty boat that is stored all summer long.
We used to remove the negative battery cable. Now that we have some solar on both, we leave it connected.