I know several folks that use them and wouldn't be without them.
Hydrocaps I think they are called. I just stick with sealed batteries
(AGM) and avoid the entire issue.

Doug

"BOEING377" wrote in message
...
Do those so called catalytic battery caps actually work? The are supposed
to
use a catalyst recombine outgassing molecules back into H2O which drips
back
into the battery cell. I am sceptical.