Laptop Battery Cells

[yawanur]

I found an old laptop battery and ripped it open because I thought I might find good stuff.

http://i60.photobucket.com/albums/h31/natewilliams82/DIY/latopBATT/DSCF0267.jpghttp://i60.photobucket.com/albums/h31/natewilliams82/DIY/latopBATT/DSCF0268.jpg
http://i60.photobucket.com/albums/h31/natewilliams82/DIY/latopBATT/DSCF0270.jpghttp://i60.photobucket.com/albums/h31/natewilliams82/DIY/latopBATT/DSCF0276.jpg

14.4v 4000 mAh!
So I'm guessing this is 8 1.8v 4000mAh cells wired in series?
What are the limitations with using these to power crazy random shit? Could I wire 2 sets of 3 in series then put them in parallel, then limit the voltage from 5.4 to 5 so I can power my fujifilm s7000 via the 5v DC in jack on the side of the camera? I could easily fabricate an attachable enclosure, and I'd obviously need a simple way to charge it.

It says never use any charger besides the original, and I can see some breadboard for the plug behind the actual crazy charging jack, but I assume the charging shit is for liabilities and I'm hoping they'll be simple to use for projects.

Oh and the purple casing is ripped because I was using a knife to pry plastic apart and it sheared the casing off, made a couple sparks. :p

[MunkeyQ]

They're cylindrical li-ions, so each one will be 3.6v.

However, charging and using them is a bit of a challenge. Here's a long post I wrote a while ago in T&T:
http://zoklet.net/bbs/showpost.php?p=506707&postcount=1

In short, to use these you'll need to hook up an over discharge circuit to prevent them from exploding if they're discharged too deeply, and buy a charge management IC. It's too risky and tricky to build one from scratch as they're pretty complex. I wouldn't advise hooking them up in strings of more than two, especially since it's an old pack. You get something called charge imbalance where during charging, a weaker cell with a lower capacity gets overcharged as the charger only looks for the nominal pack voltage. This can cause an explosion if the pack isn't shut down - quite a few cheapo laptops charge in series and simply monitor carefully for a high temp. to avoid fire. You need to charge each cell seperately with a seperate IC for each cell or pair of cells. Note that the original pack will have wires leading to the connection between cells to prevent charge imbalance.

Be very careful with the sparks from shorting out and piercing a cell too. If the membrane inside gets punctured, it will probably explode.

By the way, here's what happens if you overcharge a single li-ion cell:
http://www.youtube.com/watch?v=gCrzL82fiJ0


TL;DR: Li-ions explode.

[usernameunavailable]

Check them with a volt meter, If they are below 2.7v then throw them away. If not buy one of these http://www.dealextreme.com/details.dx/sku.12594

[yawanur]

Damnit!
:mad:
So does anyone want these or could I have some fun throwing them in a fire?

[MunkeyQ]

Damnit!
:mad:
So does anyone want these or could I have some fun throwing them in a fire?
I've built a couple of chargers around the ICs I mentioned, but I still only let them charge protected cells. Those are unprotected so I'll pass. :p

If you want to have some fun, hook one up to a car battery through some long wires and video it. Massive current + overvoltage = instant lithium plating of the cathode. As you can imagine, that reacts pretty damn fast and makes a spectacular show.

[yawanur]

I've built a couple of chargers around the ICs I mentioned, but I still only let them charge protected cells. Those are unprotected so I'll pass. :p

Anyone else you think might be interested? I'd rather see a cool project than detonate them.

If you want to have some fun, hook one up to a car battery through some long wires and video it.

:D

Massive current + overvoltage = instant lithium plating of the cathode. As you can imagine, that reacts pretty damn fast and makes a spectacular show.

Would wiring the cells in parallel set them all off at the same time, or would the current be too weak spread across all 8?

I like where this is going.

[MunkeyQ]

You can get protected Li-ion cells for very cheap prices nowadays and since this is an old pack, the cells will have deteriotated quite a lot - they've probably not got much life left in them.

Do it in parallel as the car battery has more than enough current to cause a catastrophic failure of the membrane across all the cells. It also means that when one blows and goes open circuit, the rest will still recieve their death juice.

[yawanur]

Video: Don't count on it, but it'll probably happen.

Gotta go work on a jig for this! :D:D:D