water on battery tray

[peasant]

this is where you want to run your bead of sealant (or some other kind of water deflector)

(the black bar on the left edge of the vent)

If you drive your van daily, all this water isn't much of an issue ...after a drive those "trays" are usually dry.
It's just when you're parked that the aquarium sneaks up on you. Some vans have sound deadening material in there, which of course gets damp and breeds rust.