A123 cell poped

[jimjones3630]

Have my first A123 cell pop today. If anyone has had a older lithium chemistry cell "pop" they don't really pop, it's more of a bang with rapid expanding gas and flames.

A123 pop is a pleasant surprise, I've ready how they don't rapidly expand and flame. The can is aluminum and, as I found out, easily punctured.

The how of it occurred when tightening tailcap on two A123s in a 2C Mod using a celler extender. The cell extender a tad long left threads exposed so plan on cutting the next extender down so with tailcap tight no chance to over tighten.

I like to post my goof ups to add to the watch out for this one list.
jim

 

[VidPro]

thanks, now can we squeeze some pictures and specs data out of you?

did it really BANG? not pop in your situation?
did you puncture the cell body? the spring punched through or something on the top?
which cell brand ?
how old is old?

 

[jimjones3630]

VidPro,

No bang, it was a pop. What i've read is there is no bang with A123s. The cells like all A123 cells i've had and do have came out of Dewalt 36v battery pak. what punctured was the copper braid used in the tailcap to make contact. 2 A123 cells stick out of a 2C, using cell extenders shown in pic below. Once punctured, they dumped 70A into the tailcap. I felt the heat build up first. I have had A123 cells short out in past when neg grounded. Hence, the recommendation to positive ground these things.

Yeah, I should take my own recommendations. So, felt heat then got tailcap off and tossed befor the pop. what a relief!
enjoy the pic,
jim

thanks, now can we squeeze some pictures and specs data out of you?

did it really BANG? not pop in your situation?
did you puncture the cell body? the spring punched through or something on the top?
which cell brand ?
how old is old?

 

[NA8]

Wish they'd just make a bunch of cells in regular sizes, e.g. C & D cells. Guess that won't happen though.

 

[jimjones3630]

wouldn't that be useful.

Wish they'd just make a bunch of cells in regular sizes, e.g. C & D cells. Guess that won't happen though.

 

[Alex123]

Jim,

What are using to charge these and how much did it cost?

Do you know if 4 M1s will fit in a 3D Mag host like 4C cells will with a spring flip or other mod?

Last, "the recommendation to positive ground these things", can you explain how that's done?

Thanks,
Alex

 

[warx23]

Jim,

Last, "the recommendation to positive ground these things", can you explain how that's done?

Thanks,
Alex

I would be interested in some more details about this.

Im building a c mag with 2 x A123 and would like to avoid the "pop" : ) I have the cell extender also.

 

[2xTrinity]

No bang, it was a pop. What i've read is there is no bang with A123s. The cells like all A123 cells i've had and do have came out of Dewalt 36v battery pak. what punctured was the copper braid used in the tailcap to make contact. 2 A123 cells stick out of a 2C, using cell extenders shown in pic below. Once punctured, they dumped 70A into the tailcap. I felt the heat build up first. I have had A123 cells short out in past when neg grounded. Hence, the recommendation to positive ground these things.

2A123 is a pretty tight fit for 2C so I presume you've already done this, but here's my solution to make more battery compartment space:

1) Remove swithc retainer ring, reinstall switch "higher up"
2) Grind off as much material from the base of switch at possible
3) cut down and/or compress tailcap spring as much as possible

With those three and no extenders I know I can fit AW C cells in a 2C. However, A123s are EACH >1cm longer than AW C cells.

Wish they'd just make a bunch of cells in regular sizes, e.g. C & D cells. Guess that won't happen though.

Could be a big liability if someone gets a hold of them and tries to install them in a device expecting 1.5V. This is the reason I'm nervous about having LiIon 10440 cells around, for that matter... I'd hate for someone to find out one of my AAA devices has dead batteries, and "help me out" by finding some 10440s and replacing them...

Last, "the recommendation to positive ground these things", can you explain how that's done?

Thanks,
Alex

Basically, the "traditional" way to install batteries in a flashlight is with the positive "button" facing inward, and the negative "cap" making contact with the tail spring -- a negative ground. Do the reverse, and you have a positive ground.

There are a a couple reasons positive ground makes more sense in flashlights:

• Many modern batteries have positive casings, the reason for negative ground is a throwback to the days that Zinc-Carbon, and NiCad were the only viable options, both had negative casings. Alkaline batteries actually have positive casings too, but are wrapped to "look like" zinc-carbons with negative casing, for backwards compatibility. With incandescent lamps, polarity is completely irrelevant.
• Most LEDs have positive slugs -- this is a consequence of the semiconductor structure. Attaching the die directly to a heatsink without an isolator material is most efficient for heat dissipation. If you're going to direct drive a single LED, such as a Seoul P7, or multiple LEDs in parallel, like a Quad SSC P4, it makes most sense to have the light be positive ground (so the copper or aluminum heatsink is positive), then wire the negative lead on the LEDs to the switch

 

[TKO]

Nail penetration video

 

[BVH]

I had one pop yesterday. One of 40 in 4 ea. 10-packs. It happened as I was opening up the MEC brand solderless power tube pack which uses slight compression to hold the cells in contact with one another. Was definitely a "pop" with no detectable flame (but was working under a light). The residue was about 3-5 drops of an oily substance.

 

[Flashlight Aficionado]

Basically, the "traditional" way to install batteries in a flashlight is with the positive "button" facing inward, and the negative "cap" making contact with the tail spring -- a negative ground. Do the reverse, and you have a positive ground.

There are a a couple reasons positive ground makes more sense in flashlights:

• Many modern batteries have positive casings, the reason for negative ground is a throwback to the days that Zinc-Carbon, and NiCad were the only viable options, both had negative casings. Alkaline batteries actually have positive casings too, but are wrapped to "look like" zinc-carbons with negative casing, for backwards compatibility. With incandescent lamps, polarity is completely irrelevant.
• Most LEDs have positive slugs -- this is a consequence of the semiconductor structure. Attaching the die directly to a heatsink without an isolator material is most efficient for heat dissipation. If you're going to direct drive a single LED, such as a Seoul P7, or multiple LEDs in parallel, like a Quad SSC P4, it makes most sense to have the light be positive ground (so the copper or aluminum heatsink is positive), then wire the negative lead on the LEDs to the switch

What would happen if I put my Li-Ion battery in backwards in my U2, since it is not direct drive? :thinking: Happiness or extreme disappointment?

 

[Yoda4561]

Hopefully the reverse polarity protection will work. If not you'll probably fry the emitter.