When considering the risk of doing something you also have to consider the risk of doing something else instead.
Having a modern maintenance free battery with catalytic combiners and a vent to tube inside your rv will not expose you to any harmful vapors during normal operation.
The Energy released in a hydrogen explosion depends on the volume of hydrogen/oxygen mixture available. In a modern high density maintenance free battery that would be measured in cubic inches, in a battery compartment it will be cubic feet, three orders of magnitude more energy released. A traditional battery compartment under your bedroom could be more likely to kill
you in your sleep.