Eneloop gas venting?

[JPSW44]

Hello,

I was performing a runtime test on one of my 2AA lights...I threw in some fresh Eneloops and started the test..About an hour into the test i noticed the rubber boot on the clicky was puffed out like a balloon..I immediately ceased the test..The head of the light was a little warm but not hot. When i opened the light to see what was going on there was a definite pressure release..Both cells seemed fine, nothing leaking ..Is this something I should have expected or is it out of the ordinary? Thanks.

[liveforphysics]

Warm air expands.

[Illum]

ahh no, it isn't warm air, its hydrogen.

NiMH were once considered to be used as "Hydrogen Batteries" or hybrid cars

Wikipedia: http://en.wikipedia.org/wiki/Nickel-...ydride_battery

There is an inherent risk with NiMH chemistry that overcharging will cause a buildup of hydrogen, causing the cell to rupture. Therefore, cells have a vent. Hydrogen will be emitted from the vent in the event of serious overcharging

usually this occurs during charging, not discharging, although once after using my SLPP4AA Lux with Eneloops the light expelled gas upon disassembly to charge it...so its likely that some gas is given off during discharge, and it exaggerates itself when accumulated in a sealed container upon release. My eneloops are still working today

There are also previous threads on this

[Vesper]

Searching around for similar experiences to what just happened to me... I just had this exact thing happen to me. My 2xAA Quark suddenly had its rubber clicky swell up like a grey walnut. Opened it up and the light vented out. One of the two AA eneloops that was running the thing now has a slightly bulged base on it (wobbles on its end). A bit freeky and random - the eneloops were pretty new and fairly freshly charged. Wish I knew that something had actually triggered it.

[Mr Happy]

What was the voltage of the bulging eneloop after you removed it from the light?

[Vesper]

What was the voltage of the bulging eneloop after you removed it from the light?

It's 1.31v. The other is about the same. I wonder if it's just a faulty battery from the start somehow.

[Mr Happy]

It's 1.31v. The other is about the same. I wonder if it's just a faulty battery from the start somehow.

OK, that's odd.

The next test could be to examine the internal resistance of the bulging cell. Even a charged cell might get reversed polarized if the internal resistance is out of balance. The way to test this is to measure the voltage of each cell individually while under load. Maybe the bulging cell will show a much lower voltage when you put a load on it?

[CanadianBacon]

Hey,
This happened to me before on a set of old energizers that haden't been charged for at least a year. I used them in my eagletac p20a2 and luckily, I read the instruction manual before putting in the old energizers. It said that Nimh batteries can release gas during discharge. The switch boot will be inflated.

I put in the batteries and turned on the light while letting the flashlight sit on my counter to run down the batteries (bad idea) and I noticed that the switch boot had become puffy like a marshmallow.... Good thing i read the instruction manual, I quickly unscrewed the tailcap and heard what I thought was an old man farting slowly .

Just think, if the batteries didn't come with vents, how many flashlights would be in flashlight heaven right now??

Do a few discharge cycles on the eneloops an it should be fine. After I did some cycles on my old energizers, it works perfectly with quite a long runtime.

Good luck!

[Dry-cell]

I'm slighty concerned about gases venting also. In the Eneloop handbook.pdf they tell you not to use them in underwater lights because of the gases they vent. Should we be concerned about IPX standard lights and gases not being able to vent from them?. Normally I remove batteries from device's if not in use for more than a week. For people that leave them in until practically drained, over a long period of time, they should be concerned, right?.

[Lynx_Arc]

Just don't breathe the gas vented..... could make you loopy

[ecrbattery]

This tend to happen to 2AA flashlight that use a low voltage 0.9V-4.2V driver and an imbalance set of battery. These driver keep on drawing power even when the voltage drop below the safe 1.8V (0.9V per cell).

When you have 1 cell at 1.0V and the other is empty at 0.0V, the driver still pull power and cause the empty cell to reverse polarity. Then the empty cell will vent hydrogen gas which lead to the bulging rubber boot.

The reverse polarized cell can be fix by simply charging it again. However, there will be permanent damage to the vented cell. From my own experience, my Rayovac Hybrid AA suffer a permanent lost of 100 mAh in capacity after it vented from reverse polarity in a high power (1A) 2AA flashlight. If you use the damaged cell again in the 2AA light, you are creating an ideal condition for the venting to occur once more time.

Many battery manufactures contribute to this battery imbalance problem by only offer charger that require you to charge in pair. (Sanyo NC-MQN06U)

Pair charger + imbalance cells + 2AA w/ 0.9V driver = free hydrogen generator

[beerwax]

so which 2 aa torchs have driver that cuts at 1.8volts. and wouldnt that interfere with folks that like to run alkalines?

[Lynx_Arc]

so which 2 aa torchs have driver that cuts at 1.8volts. and wouldnt that interfere with folks that like to run alkalines?

The only 2AA torch I know of that cuts out around there is the newer minimag LED it cuts out about 2v or so. At higher current levels there isn't much left in alkalines at 1v each anyway, maybe a few hundred mah at 50ma or less current.... less than 10% I would guess.

[beerwax]

if i give someone a 2 aa light as a gift, they will stick alkalines in it, get crappy performance on high, voltage drop rapidly, but itll still work and for some time. if its got a voltage shut at 2 volts.. gee i dunno. 200 mah at 50ma is 4 hours of a small amount of lite, but that might be better than shutting off. nothings ever simple.

[Lynx_Arc]

if i give someone a 2 aa light as a gift, they will stick alkalines in it, get crappy performance on high, voltage drop rapidly, but itll still work and for some time. if its got a voltage shut at 2 volts.. gee i dunno. 200 mah at 50ma is 4 hours of a small amount of lite, but that might be better than shutting off. nothings ever simple.

The problem with giving LED lights to people is they won't buy but the cheapest batteries that will fit in them so you are better off buying them cheap lights instead of good ones because the good lights tend to want better batteries or rechargeables. I have a dorcy 2AA 80 lumen light that will work down to about 1v and I think takes about 700-800 ma off fresh batteries.

[ecrbattery]

The Liteflux LF3XT (with the 2AA extention tube) is one high power light with a programmable cutoff of 1.8V.

For casual user, it is hard to beat the Home Depot Husky 1AA LED flashlight. This was available during xmas time for $5 per pair. It is as bright as a regular incandescent MiniMag 2AA. A good alkaline AA will power this light for a solid 8+ hours then go into a "glow" mode. Before giving them away as gift, I usually drop in a Energizer L91 Lithium AA which will run for 24+ hours. It is a "vampire" light so it will COMPLETELY drain all battery including rechargeable.

[yliu]

I had 8 brand new, freshly charged eneloops in my TK45. Devided to do a runtine test, after 15 minutes I saw that the 2 switches were puffed, so I immeadetly stopped the test. There were no damage

[ico]

Can the eneloops still be used after they have vented out some air/hydrogen as someone said?