Caravan Battery Box Vented?

Some year ago I had a battery with a vent tube, insult drilled a hole in the bottom of the batt box and pushed the tube through  to vent outside

So did my son in law and then wondered why every time he opened a tap water flowed across the floor!!He had managed to drill exactly through the centre of the semi rigid cold water pipe!!!!On a serious note.......There should be no need for the breather pipe to be used in a caravan and .....no battery boxes on caravans are not vented.

Motorhomes have internal battery boxes and there is a vent tube to the outside, however, assuming your caravan battery is in an external enclosure then it should be naturally ventilated so you wouldn’t need to use the vent tube.

Our neighbour had a caravan where the battery was accessed from inside the caravan ie it was fitted to a battery box in the floor of the caravan, I'd imagine that would have needed the vent tube, but battery boxes fitted into the side of the caravan are unlikely to be sealed from the outside world.

If that were the case why do they normally have a rubber seal.?l.  not just to stop water ingress?

Good point. Under normal conditions a “sealed” battery does not give off Hydrogen but it is possible that, for example, a charger failure can cause the battery to emit Hydrogen which could certainly be hazardous within a motorhome or caravan. I can only assume that the risk is deemed minimal in an external locker sealed to the inside of the van. 
I have to say though that my motorhome had a rather flimsy plastic internal box with a loose fitting cover and straps. The vent tube to the outside was also quite flimsy.

When I had massive battery banks in the bilges of my yacht, I didn't have a vent. Fitting one would have created BIG problems. 

There's a rubber seal around most of my battery locker, but it's not water or air tight as there's a bit missing at the bottom where there cable goes through the edge of the door. But it's enough to keep the box fairly dry.

We ran an Eriba caravan for 13 years.  -German caravan with German battery installed in German fashion in  locker under the bed. No battery box, no venting, no seals, no problems, no deaths.