NiMh and hydrogen

[MarkH]

I've used NiMh AA batteries for my strobe and flashlights in the past. It seems like you digital dudes use them quite a bit too. Here's my question: Are you worried about hydrogen build-up? At the end of my dives a couple years ago, my small hand-held flashlight was bulging almost like a balloon from the emitted hydrogen. The last time I used them was the dive when I heard a pop and noticed that the back of my strobe had shattered and blown off as I ascended in the shallows. I haven't heard of any problems with them from you guys. Were my batteries just crazy?

 

[Dee]

For several years S&S advised against using NiMH in their strobes for fear if it flooded the NiMH and saltwater reaction would cause an explosion. Then last year they replaced the battery caps to a design that would allow off-gassing in case a flood occured. Since then S&S has given the OK to use NiMH in their strobes.

That's the only explosions I know about regarding NiMH batteries.

 

[Scubaroo]

Check out the thread and pictures posted just today of an exploding Princeton Tec surge light on TheDecoStop from NiMH batteries.

 

[nwdiver2]

Most strobe that use NiMh batteries have isolated the battery compartment from the electronics it, is interesting that Ikelite has done this for many years to prevent catastrophic floods. The problem is if salt water hits a NiMh it off gases allot of hydrogen, this would fill a strobe with hydrogen, a signal to the capacitor to fire and boom.

I believe this is why Nikon offered to replace 62,000 Nikonos 103 strobe with the 105 for free. Several accidents may have occurred. This recall did not take place until NiMh batteries were widely available and the instruction for the 103 said use AA batteries.

Sea & Sea was covering itself with its strict instructions not to use NiMh batteries. It seems they have changed their designs and no longer need to warn off people about their use. They have not done any recall beyond replacement of the battery compartment cap, which does vent if there is a gas buildup.

It is also interesting to note most designs with rechargeable pack are not a problem; this is because rechargeable packs are made up out of NiCd not NiMh batteries.

 

[slowhands]

I got a new Sea and Sea strobe, the YS-90DX. The instruction book said to use only batteries in a list: alkaline, ni-cad, or lithium. But a pink addenda to the book said NiMH batteries were OK, with a lot of cautions about how to use them. I understood the YS-50 was the strobe that had a new battery cover retrofitted, due to 2 cases of exploding batteries (one in the US and one in Japan at a service center). So I think S&S were just being cautious, wait and see how the 90 behaves with flooded batteries and the new battery cover with a purge valve. Must have been OK, since they officially blessed the use of NiMH batteries in the new model.

Incidentally, the battery compartment is totally separate from the main electronics compartment, so a spark could not set off an explosion (at least for the YS-50 thorough 90, all have a similar body). There was simply a pressure build-up in the battery compartment, so when the door was removed it hit people in the face.

Even though Ni-cads have some advantages over NiMH, I think they will cease to be offered in new designs. Cadmium is considered toxic waste (like lead and mercury), and its routine use in new products is discouraged ). Anyway, the strobe vendors seem to be able to cope with possible overpressure due to flooding, it's a non-issue for new designs. If you have an old YS-50, better make sure the battery cover has the retrofitted purge valve, just in case.