Is this a new Warning? Is there a reason why? :~
I was planning on purchasing a 4 pack of Eneloop Pro AA (BK-3HCCA4BA) for my new Nitecore EA41 Pioneer but I changed my mind after reading the Caution on the back of the pack: “Do not use in water proof flashlights or any device with an air tight battery compartment”
Same CAUTION is on the back of the Eneloop pack sold at Costco with (10) AA, (4) AAA and Charger (Item#906576)
It is a new warning. I had a couple of the eneloops outgas in flashlight recently. 
Me too. Of course it wasn’t a stock light. I pulled too hard on them. Melted the battery carrier & gassed out a cell.
Hey, but who cares! I am no expert, but I don’t think there is enough gas in 1 cell to make the light explode. But, I am a idiot, so don’t listen to me.
ANY battery technology can out gas and none of them should be in air tight or water tight containers. YES, that includes all of your flashlights that are water tight to a certain depth, meaning just about all of them. Yes, any of them could allow for cells to create a buildup of gas pressure and yes, bad things can happen to any battery, even alkaline. I've seen that too.
Have you ever noticed most everything else "electronic, with batteries" will allow for water to leak inside, if dropped in water? It's because that means air can escape too, so venting can occur. They design them so batteries can vent, instead of building up gas and exploding from the pressure. Flashlights are basically little pipe bombs and more unsafe than many other battery operated devices.
Because we can make depth charges… We can sink submarines!!! 
I use them since June (from ChibiM) in a EA4 inside a car, no problem.
OL said about what I was going to post but said it better. Basically the new warning is lawyer speak, presumably after some incidents of using Eneloops in lights which tried to discharge them faster than designed. IMO not surprising when you consider how fast the new Thrunite Neutron AA light tries to discharge them and lord knows about user modified lights.
do you have links to these?
Jeez, and here I’ve been diving for almost 20 years with NiCads, NiMh, alkaline, and now Lion all in WATER tight containers! Kee-rist! I coulda been killed! 
Why didn’t anyone tell me? :quest:
The problem arises when you push the battery well beyond it’s specs, then it may out gas. Obviously you do that TOO much and you have a pressure bomb. Know the limitations of your battery and device, use accordingly and you will be fine.
When that water tight light somehow fails to fulfill that specification and saltwater leaks in, the electronics go kinda berserk. The corrosion as those batteries dump is pretty nasty.
The cell contains no gas at all (or very little anyway). Dont view as a container of gas and thus its size being the limit of gas. It has chemicals in it, solids, and they convert to gas. When it starts to gas, there is considerably more gas than the package of the cell would imply.
Cuz we want you dead so we can inherit your lights… J)
Bort;
Note that I said “presumably” about outgassing and as the new Thrunite Neutron claims 480 Lumens on one AA and 800 with two then I am again presuming that the current draw is ridiculous. See the Potential Issues section of Selfbuilt’s review on CPF where he notes issues with single AA operation on one light and too great a current draw from 16340 batteries other than IMR versions for the CR123a/16340/18650 Neutron. Unfortunately he does not give any current readings.
Sorry but as an ex quality assurance test and specification compliance test engineer I tend to interpolate and combine data from multiple sources and keep asking myself how things can relate. Over the last year or so a combination of increasing light outputs from new relatively small lights and more junk batteries out there has made me more concerned about safety issues. Just a bit surprised that apparently one of the first warnings comes from one of the best batteries available via this outgassing warning. Got a feeling that at the extreme of performance this warning may apply to ALL NiMH chemistry batteries and sealed lights.
I’ve had my my quark aa2 tactical tailcap switch ‘expand’ like 3 times in over 2 years. It became quite hard to press. I knew it was some kind of gas buildup at the time. I figured it was somewhat dangerous and each time, I recall putting the light out and waiting some time before unscrewing the tailcap out….
Which it does.
hope it doesnt become an issue since im running AAA eneloops in Olight O’Pen-
Been using them for years, they’re just covering their butts.
What’s that saying? “Remove the warning labels, let the problem sort itself naturally”
:bigsmile:
If you are concerned about NiMH being a problem when enclosed, think about your 18650 lithium batteries… Now that’s a nice pipe bomb!
I think it would be a nice protection to include a safety vent in all flashlights. That would be cheap, stop water from coming in but the seal would break if the cell inside vents.
well then i think i should stop worrying about it
You mean a Flapper Valve. I’ve seen such a thing on Safety Flashlights at the chemical factory. They are basically little holes in the flashlight body with a flap over it. I forget who makes them, but I believe they were Streamlight Xenon 3C models…
This quote is full of win