[bushpilot]

was it SMOKE (from where) or misting battery acid (neither is good).
even SEALED (lead acid) batt's can be checked for fluid.

i would IMMEDIATELY pull that battery and test it, and check to see if its been "boiled" dry by the charger.

i NEVER EVER use a trickle charger - they will over charge a battery and boil it dry....
the internal chargers in most coaches are trickle chargers and need monitoring of the batteries to make certain they do not boil the batteries dry.

when i park our coach i disconnect the batteries and connect an INTELLIGENT battery maintainer (battery tender or battery minder) - intelligent chargers will adjust their charge output based on the batteries condition (lowering the change when the batter is "topped off").