Thats the problem some of these nights will be in the 20's so furnace will run often, and ETI will not put the batteries in the heated space any more on the 19 models , so they will be out in the cold and lose some power that way
The batteries can always be relocated. As part of my custom A/C retrofit I moved the dual 6V's from the tongue into a vented box under the passengers side dinette seat. I'm told this is the location that they resided on the very early 19's.