Originally Posted by Airstream 65
The black box in this case, is not really a black "box."
It's a special made battery enclosure made specifically to fit within the battery door setup that Airstream has used for many years, that encloses the battery on three sides and the top and bottom. The fourth side faces the battery door that opens with a key, which allows you to check the battery, to remove the battery or to replace it.
Unfortunately, they are made specifically for Airstream, and to be safe, nothing else on the market will fit, without a lot of scabbibg around.