How come? [lithium vs alkaline flashlight]

Here are a set of newbish questions I was embarassed to ask, but due to recent cr123A accidents I realized its best to ask...since its feeling like an itch in the back of my head.

The diving class lights, such as the SL PP have one way vents and hydrogen catalyst pellets.
they use Alkaline batteries, which vent substantially less than their lithium counterparts.

Lithium flashlights, though many have vent caps, few I've seen hydrogen pellets.

Recent CPF news continuously report lithium batteries venting [rapidly with flame] causing several flashlight explosions.

Why do the Alkaline flashlights need the catalysts and the vent if Alkalines vent less than lithiums? And what does the catalyst pellets do with the hydrogen?

In alkaline chemistry batteries, hydrogen is a normal byproduct of the chemical reaction which produces the electric output of the cell. In LiMnO2 chemistry, there is no gas byproduct of the reaction in normal use. The venting that has occured is rare and abnormal. Hydrogen catalyst pellets are not needed in a flashlight designed for lithium batteries, nor is a vent needed. Flashlights which are gasketed (sealed) and use alkaline batteries will have hydrogen gas collect within the flashlight during normal operation. This is why there is a vent and/or hydrogen catalyst pellets. The violent venting of the lithium powered flashlights would probably not really be lessened much if there was a small vent(as they are on alkaline powered flashlights), as it seems to be a violent reaction.

Illum_the_nation said:

And what does the catalyst pellets do with the hydrogen?

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The catalyst converts hydrogen together with oxygen into water. This is happening continuously, so that the hydrogen level is always small and way below the explosive concentration.

Check this one out. Li on batteries do their overheat thing in a laptop.

http://www.pcstats.com/NewsView.cfm?NewsID=50846

Gary

Are NiMh producing H2, or only the no rechargeables?

fasuto said:

Are NiMh producing H2, or only the no rechargeables?

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As I can recall, NiMH batteries have their own catalysts to deal with hydrogen production during overcharging. However, I don't know whether this is a standard construction element in all rechargable batteries. Somebody more familiar with the technical details might provide some insights.
After all, the chemistry of NiMH are based on hydrogen that are chemically bound within the batteries. I am not sure, whether there are possible failure conditions (e.g. high temperatures behind the windshield of a car) that would allow to set this stored hydrogen free. Anybody has some info about that?

drmaxx said:

The catalyst converts hydrogen together with oxygen into water. This is happening continuously, so that the hydrogen level is always small and way below the explosive concentration.

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Don't you have to toss out and replace the catalyst with a new one everytime it gets wet? then..ugh

Illum_the_nation said:

Don't you have to toss out and replace the catalyst with a new one everytime it gets wet? then..ugh

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There is not enough water produced fast enough to get the catalyst pellet wet. Additionally, a catalyst has the unique feature that it does not get destroyed by the reaction itself. If the pellet actually get's wet (e.g. by water leaking into the flashlight), then just dry it out and it should be fuctional again.

Gotcha, thanks

found this on youtube.com

http://youtube.com/watch?v=SQ0SNESIkWk&search=explode battery

these guys are intentionally overcharging the batteries with a car battery i guess....

AtomSphere said:

found this on youtube.com

http://youtube.com/watch?v=SQ0SNESIkWk&search=explode battery

these guys are intentionally overcharging the batteries with a car battery i guess....

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Wow, these are impressive demonstrations about exploding batteries. Nothing I want to have on my lap(top) while happening.

Poor cells....poor car battery too

Lithiums can give out alot of amps...but what they were doing is essentially shorting out the car battery too

AtomSphere said:

found this on youtube.com

http://youtube.com/watch?v=SQ0SNESIkWk&search=explode%20battery

these guys are intentionally overcharging the batteries with a car battery i guess....

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Those are LiPo batts - different animal than lithium primaries or li-ions.

greenLED said:

Those are LiPo batts - different animal than lithium primaries or li-ions.

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what are LiPo? Those non-rechargeable lithum batteries like those from surefire?

AtomSphere said:

what are LiPo? Those non-rechargeable lithum batteries like those from surefire?

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I believe it stands for Lithium Polymer, its a form of Lithium cell that can be made into unusual shapes and sizes to fit a specific volume...it works the same as a lithium-ion. Apple's IPod and PDAs use Lithium polymers because they can be made to literally credit card thicknesses.

earlier models explode like bombs when overcharged, but recent versions are stable to handle low drain to moderate drain requirements.

heres a few good links on LiPo
http://www.plantraco.com/hobbies/product-lpcells.html
http://en.wikipedia.org/wiki/Lithium_polymer

Illum_the_nation said:

I believe it stands for Lithium Polymer, its a form of Lithium cell that can be made into unusual shapes and sizes to fit a specific volume...it works the same as a lithium-ion. Apple's IPod and PDAs use Lithium polymers because they can be made to literally credit card thicknesses.

earlier models explode like bombs when overcharged, but recent versions are stable to handle low drain to moderate drain requirements.

heres a few good links on LiPo
http://www.plantraco.com/hobbies/product-lpcells.html
http://en.wikipedia.org/wiki/Lithium_polymer

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ah ha! thanks for the note! kindda feels like i am carrying grenedes with me all the time after watching that video

AtomSphere said:

ah ha! thanks for the note! kindda feels like i am carrying grenedes with me all the time after watching that video

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after seeing the video...I think I have 6 unpinned grenades on me plus another 6 worth of spare "grenades" as if in preparation in case the 6 in my lights are all duds....

http://www.rcstuff.us/battery/lipo/lipo_DNA.html
Heres some more fun with LiPolys.

Now now, let not have any bad intentions after watching these videos