A123 cell has a puncture,is it usable?

[liveforphysics]

Yes! Dave's idea is much better. Connect a car headlight or brake light lightbulb across those terminals, and let it sit for a few days until the voltage reads 0.2v.

Put on safety glasses, a plastic face shield, a respirator, long plastic gloves, and cut away the foil off the top of the pouch. Then, the safest option would be submerging it outside in a bucket of water for a day to make sure everything is fairly neutralized.

Then begin dissecting (with proper safety equipment on, outside or in a place with excellent ventilation).

[flexy]

I was thinking along those lines, or that gear Ypedal's wearing


This ingredient breakdown was on the docs that came with the cells, not sure if it applies to these cells in particular or it's just safety guidelines for generic lipo.

http://dl.dropbox.com/u/8208701/Electric%20scooters/lipo%20chemicals.PDF

[JRP3]

Is there really that much potential for mayhem with a fully discharged LiFePO4 cell? Especially when I've seen some of you guys holding smoking cells of more volatile chemistries in your bare hands

[liveforphysics]

Is there really that much potential for mayhem with a fully discharged LiFePO4 cell? Especially when I've seen some of you guys holding smoking cells of more volatile chemistries in your bare hands

The A123 pouches can be pretty touchy. If I was doing it myself, I would just cut into it with a razor knife and bare hands and get it done. But I would never encourage anyone else to take my approach, too many things could potentially go wrong, and too many nasty solvents and chemicals that might hurt someone who is into doing the longer-term-staying-alive thing.

[potatorage]

I had a cell that wasn't as tight as the others, but I don't see any noticeable flaws. Is it safe to use?

[flexy]

I have taken the cell apart, here are some pics.
There was a strong sweet smell from the liquid inside ,this soon evaporated.
You can see where the cell was originally punctured the cathode/anode has started to degrade. there were about 60 layers altogether.

Hard to see what might have been out of alignment, without a reference to compare to. I did notice on some of the others what appears to be loose bits of tape, trapped under the case, causing an uneven surface. This might cause problems when they are all under compression in a large pack, causing them to be rejects.





All photos here https://www.dropbox.com/sh/kmnlhfj21ibb22i/Ip4onBU4xq

[bigmoose]

Flexy, THANKS! Outstanding execution of a Destructive Physical Exam! I would bet the "bump" I fell down the center of one of my cells is a full wrap of that green tape. Looks like a straightforward zig zag of the separator with alternate cathode and anode. Each with a tab at the top of thin foil that gets ultrasonically welded together to thick tabs to exit. The kapton tape around the ultrasonic weld almost looks hand applied, but that can't be true. Interesting that there are 3 or 4 layers there. Would have thought automating the process would be one layer of a thicker kapton...

Your capture of the degradation of the plates once the foil pouch was cut is priceless! Thanks again for doing this. We have all learned from your bad cell.

[flexy]

The kapton tape around the ultrasonic weld almost looks hand applied, but that can't be true. Interesting that there are 3 or 4 layers there. Would have thought automating the process would be one layer of a thicker kapton...

There is just a single layer of kapton either side of the weld.
Most of my cells had small dents on the tabs like they had all been tested with a voltmeter by hand (Victpower Quality Control?)
I also had one labelled "test" which had a lower reading than the others, that's not getting picked for the team either!

[bigmoose]

Good catch where the eye is better than a photo! Here is the area that interested me, can you tell what the other two "films" or tapes are that have straight cut edges. So the serrated edge is a single kapton tape.

kapton.jpg (91.82 KiB) Viewed 141 times

[flexy]

The serrated edge is where the kapton tapes from the front and back of the terminal weld come together.
The other cut edge is the bottom of the slightly opaque plastic (or teflon as some have called it) which surrounds the terminal where the top of the pouch is sealed.