Our good colleague at Wetpixel, Adam Hanlon, recently reported that the extremely popular Eneloop rechargeable batteries are now not recommended for underwater strobe use. Panasonic, who owns Eneloop, specifically states on its website "Please do not use eneloop Ni-MH batteries in underwater lights or other airtight appliances." Adam mentions it could be interesting if the strobe manufacturers have something to say, otherwise we’ll all keep using Eneloops as usual. It could indeed.
What seem to be the issue?
Damaged Ni-MH batteries can release hydrogen gas. The batteries are equipped with a vent that will release the hydrogen. In air this is not a problem but if the batteries are in a seal device where the gas cannot be diffused a spark caused by a hyper-electric discharge or short circuit could potentially cause a fire. That said, most contemporary, if not all, strobes and dive lights do have a release valve whereby the hydrogen gas can be vented from the battery compartment.
On a related note
In February, DPReview published a test by Martin Cheung, in which the recycle speeds of inexpensive rechargeable IKEA LADDA batteries were compared against more expensive Panasonic Eneloop Pro batteries using Godox TT685 flashes. The results were surprising: the LADDA batteries actually demonstrated a noticeably faster recycle speed versus the Eneloop Pros. (see link below)
Are they the same batteries?
These surpring findings led other bloggers to speculate what the difference between the two brands really was, if any. For example Petapixel ran an article asking “Are $5 IKEA LADDA Batteries Identical to $20 Eneloop Pro Batteries?” Apparently both brands of batteries are made by the same factory in Japan.
Are IKEA LADDA Batteries Really Eneloop Pro cells?