most all the consensus here is right on the mark -
I built canister lights and have found that the NiMH are great as they hold the charge long. Any battery is ging to offgas during charging and discharge, you can't get around it - this is the reason you don't see a lot of sealed battery comparments...
when selecting cells, one always have to look at a number of things - for instance, not all NiMH cells are equal, you can use a high AmpHr Panasonic cell, vs, a lower AmpHr powerstream cell, but the PS may have a more even discharge voltage, meaning that in the long term, your light will burn longer before the voltage drops below what the bulb needs (this applies to HIDs - not halogen).
Anyway - there are no dangers from explosion of a NiMH battery in a scuba canister - there are other applications where you may have issues, but this is not one of them.
HTH,
Dane
