Evisceration of the LiIon

You can smoke a cigarette while pumping gas a thousand times, and only be engulfed in a ball of flame once.

Does that mean that the stories about gasoline's explosiveness are exaggerated? Even if they are, does it mean that you shouldn't still be careful around gasoline?

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Have you ever tried to ignite gasoline with a cigarette? It is more difficult then to ignite a cigarette from the soldering iron.

Oh yea. Socially conscious, environmentally friendly, safety first and that kind of stuff. What happened to the explorer spirit of the heroes of Jack London and Herman Melville?

Well. If SLA or NiMH is shorted, it will boil and pop as well. The main difference is that the LiIon stuff is flammable.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Let it go, Tim. You can't fix stupid, you just bury what's left.

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Interesting, thanks for the report. Of course, once you'd opened the containment, there was nothing to contain a pressure buildup so it was to be expected that the oxidation of the Li would be rather less spectacular than it might be.

Hit a lithium with a hammer and see what happens..... entirely at your OWN risk of course. Don't blame me if you seriously injure yourself.....

You can point at it and laugh, to prevent the marginally smart from falling into the same hole.

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Certainly, but don't expect anything else positive from the terminally stupid.

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There are different constructions of LiIon.

Have been recovering the paste-former perforated metal from early prismatic cells, at various times for varied re-use. This paste will glow red hot and burn on exposure to air in exothermic energy release, so disassembly is best performed under water, where decomposition still occurs, but in a less dramatic manner. Opened cells are likely to retain their pre-fusing charge.

I store old cells, individually isolated, in a fire-proof, air-tight metal container.

By the way, you don't want to be accidentally getting too much free Lithium into your system, as it may have serious side-effects .....though some posters might benefit from a more controlled version of this kind of therapy.

RL

Admit it, you want everyoe to mail them to Phil.

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And the burn products corrosive eg LiOH. Don't breath it in.

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Dirk

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That's really interesting, I've never deliberately tried to dissect one of those cells. Here's some ancillary info which may help explain why you should be wary of Li-ions.

(1) There are different Li-ion chemistries. Some, like the Ovonics one, are safer. In general the battery manufacturers are in an arms race to get the best energy density though, and high energy density generally means high short circuit current and high temperatures when shorted! I have seen solder melt when shorting Li-ion cells (we were interested in minimising the short circuit temperature and had a sensor attached by a loop of soldered wire).

(2) You know all those tight charging conditions? And about Li-ion safety IC's? (Buried in the end of Li-ion cells is a tiny PCB with a window comparator and a dual FET, which will isolate the cell if its voltage falls below about 2.7V or goes above about 4.2V.) If the battery goes too far out of the 2.7 to 4.2V range, metallic lithium separates out. Consider: if the lithium is bound to something else, and is exposed to water, it ain't too much of a problem. To burn, it has to first be stripped out of whatever it's in, so the reaction isn't *too* exothermic. But if it's metallic, AND the battery gets punctured, well now you've got problems.

(3) Battery manufacturers consider 1 million cells a day to be a small manufacturing run. Some cells WILL get punctured. For example I've seen one that got smashed open down a mine, when a train ran over it. So the reputable battery manufacturers WILL NOT sell the cells without the safety circuits.

(4) Some dodgy manufacturers save 20 cents by missing out the safety circuit. (I recall being approached by a Chinese outfit I'd never heard of who guaranteed to undercut our supplier. "What about the safety circuit?" I asked. They referred back to their factory... no one even there knew what I meant.) Now, bear in mind the stories you heard 3-4 years ago about Nokia phones exploding when charged, and Nokia investigating and saying "these were not Nokia batteries, the users tried to use cheap ones"... of course Nokia still got the blame in the media.

(5) The laptop batteries that smoked in an exhibition a year or 2 ago were a different problem. Something about pushing the energy density too far for the state of the art, ended up with microscopic shorts between electrodes, across small particles inside the battery.

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Nemo

I bought a used laptop about 1 year ago and bought a new spare Li-Ion pack to go with it. The application for the laptop faded out and it sat for 1 year. I recently found a new use for the laptop and found that both the batteries were flat and would not take a charge.

Being a EE I thought I would try to learn something about these batteries, so I read all I could find on line and found 1 vague reference that recovering these flat batteries was "difficult". Several of the references I read said they were completely unrecoverable.

Since the built-in protect circuit prevents re-charging them when they are flat, I painstakingly opened the plastic case the 8 18650 type cells were in. (I don't recommend any non-EE try this). I then attached a few short leads to the actual battery pack itself so I could hook up a an external variable DC power source. I verified the pack voltage was about 1 volt or less. I set my external power supply to 1 volt and attached it to the pack. The pack acted like it was a high internal impedance. So I only applied .1 to .2 amps and let the pack sit. The current slowly went down and battery voltage slowly rose. So I slowly adjusted the voltage a bit higher every 10 -20 minutes in a time consuming process. I was working on another project at the very next workstation, so I was almost continuously monitoring the process.

Slowly over a period of 8 hours, the battery pack voltage eventually reached 15-16 volts. I let the pack rest overnite and then checked the voltage the next day at 13.5 volts. I put the DC source back on and let it sit for another day at 16 volts. I checked the impedance of the pack and it tested good. So I glued the plastic case back on the pack and put it in the laptop. The computer said it was at 16% and working. I let it charge in the computer with the computer off for 8 hours. It then indicated 90% charged. I played a DVD move for 45 minutes as a test and it said it still had 44% of charge after 45 minutes of use. This was similar to a test I ran when I first got the laptop.

I am now doing the same thing with the second battery pack. It appears to be responding the same so far. I don't know how long these batteries will last, but I just wanted to share this information.

The hardest part of the process is getting the plastic case apart in a fashion that will allow it to be glued back together. This is so difficult that I do not recommend this process to anyone.

(snip)

The protection module effectively isolates the pack from further discharge once a preset threshold is crossed on discharge, usually around 3v0. In that "isolated" state it presents a high (but not infinite) impedance to charge attempts.

Decent Li-Ion chargers sense the pack terminal volatge with a minute "qualifying" charge. If the pack presents as high impedance, most of them simply offer the normal "current-limited constant voltage" charge mode with the charge current limit set to a very low figure, and WAIT.

The packs almost invariably will charge slowly and get back into the "green" where normal charge proceeds. The caveat here is that the packs may have suffered chemical deterioration from extended time at a depressed voltage - the

3v0 cutoff isn't for a whimsical reason, it is to prevent cells deprtessing to below about 2v5 where this deterioration occurs.