I have a slide-in camper with batteries located under a step up to the cabover portion. They are however covered by a plastic box underneath the step and vented to outside. It would take a lot of hydrogen buildup in a leaky AD cab to get to the point of going BOOM with an errant spark.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.