Not on a charger, but I did have a battery explode in my Toyota Camry when I turned the key to start. I unfortunately don't remember what happened to the battery as far as if only the caps blew off. But I do remember the whole car shuddering when it went off. Fortunately this happened in my driveway so I was able to quickly douse the engine compartment with copious amounts of fresh water from the garden hose and prevent any acid damage.
As far as charging in your TH; An RV is far from airtight and I can't imagine any appreciable buildup of hydrogen. With an automatic maintainer I would probably let my batteries charge. But I would also shy away from the $4.99 Harbor Freight tenders as I've had a couple of those fail on me. One stopped charging and the other was overcharging at something like 16 volts.
