Sealed battery in pressurized compartment

["asmyth" <asmyth@hsomail.com>]

Hi guys,

I am thinking of putting sealed AGM batteries in a pressure-compensated
compartment. I believe the batteries have some kind of gas vents, but I
imagine they are designed to vent only outwards. As the compertment pressure
increases, this will put a squeeze on the battery cases.

Is this as simply as drilling a very small hole in the top of the batteries?

-Alec Smyth
PS: dive depth is unknown as yet, but presumably quite deep (its not a wet
design)