Salvaging laptop lithium-ion packs

[Chrontius]

I have an old Dell CF623 given to me when it was replaced, for "Recycling."

Yeah, I'm going to recycle it right into my spares bin. The trick is that it seems to be assembled with some kind of solvent cement?

I guess what I want is to figure out how to take this apart, safely, and make a place where people can go to figure out how to go about this (admittedly risky) task with a bit more insight.

 

[lolzertank]

I use a retractable utility knife. I retract it almost all the way so it doesn't cut the cells. There should be a seam somewhere where it's put together. Carefully cut that with the knife and the battery pack should come open. Then, you need to cut the tabs. I use a plain old pair of scissors. Be careful not to short the cells with your scissors since they will vent with flame. A bit of cutting later and you've got yourself some 18650s.

 

[Chrontius]

Protips:
The Dell CF623 is held together with lots of glue. The edgecrusher method works, but you'll need to go around the edges with a flathead screwdriver, prying apart the overlapping plastic.

Cut all the wires off the cells first.

Cut all the cells apart starting at the - end. The cans are all electrically identical, and you're less likely to cause a short with your cutting tool.

 

[Justin Case]

Googling variations of "open laptop battery pack" gives lots of useful hits. I used this one several years ago to open a Dell pack: http://www.insidemylaptop.com/open-take-apart-dell-laptop-battery/

 

[Chrontius]

Good link, but the construction has changed. There's no way to get into this particular 9-cell model without destroying the pack but good.

 

[clintb]

Just tonight I tore open the pack from my wife's Gateway tablet pc. It was plastic welded (shut for good!), so I had to just pry it open. It was easy enough, and I got six good 18650 cells out of eight. They're on the charger now. :)

I love being "Green".

 

[Chrontius]

I got four good cells of nine.

Three were at less than 0.1 volt, and will be recycled tomorrow.
Two, when placed under the negligable load of a multimeter, went from 2.5 volts down to 1.8, and scare me. They're sleeping outside tonight under a flower-pot heat shield, next to a swimming pool (for pushing burning things into)

Four were idling at over 3.7, and while still sleeping by the pool (in ziplocks, of course) will be kept for reuse.

 

[Hallmcc]

I had often wondered how much damage occurred to these cells after sitting discharged for long periods.

I purchased a second Pila charger (so I would not cook my only one:)) and took a four year old Dell apart that had been collecting dust for over a year. Inside were six cells. Two were at 1.1 volts, two were at .86 volts, and two were at .76 volts. All considered damaged and unusable.

Being the knucklehead I am known for, I decided to sacrifice the Pila and see what happened when I tried to charge them. Pila manual states that it analyzes the batteries first and won't charge a battery below 1.0 volts. I started with the two that were over 1.1 volts. Took everything outside on the patio off the garage and started a charge cycle. Using my trusty index temperature gauge I checked the cells for over heating every few minutes. They never even felt moderately warm, their temperature did increase slightly over the cycle but never got close to overheating. Three and a half hours later, at 4.18 volts the leds went green. I took them out and put them on a shelf for testing later.

I did the same procedure for the other four cells, charging them in matched pairs and monitoring their temperatures with my trusty finger. The Pila charged them all, even the ones that started at .76 volts. Upon reaching 4.18 volts the charge terminated.

Four days later I checked the cells and they had all settled to 4.13 to 4.14 volts. Tomorrow I am planning to load test them and see if they can stand up to any use at all.

Is it possible they could actually handle a load at all?

 

[Hallmcc]

Today I started testing the 18650's, I started with the worst of the bunch when I stripped the pack.

It was one of the two that started at .76 volts. When I started the test the amp meter was reading 1.09 amps. At some point between 20 and 25 minutes I noticed the amperage draw had dropped to .77 amps and stayed there for the rest of testing time. I guess I should have paid more attention. I don't have any automated testing equipment so I was using the same DMM for the voltage and amperage tests. I would have to disconnect the DMM switch it and test voltage every five minutes. I am sure the change was my error.
The cell is an unknown, unprotected, 18650 from a four year old Dell. I believe it is an 800mAH. Anyway here is the graph. Does this look right?

 

[bshanahan14rulz]

I got 6 LiPoly cells out of an apple macbook pro battery. All were in great condition, with resting voltages of 4.12 (well, one said 4.11, but that could have been read error...)

They are sony branded, dimensions:

cell: 90x40x5mm
actual (taking into account the width of crimps, extra material, etc.)
65mmx43mmx5mm

tabs: 7.5mmx5mm, about 5mm apart and about 10mm from a side. Tabs are on the 40mm side.

 

[Chrontius]

Hallmcc:

You should consider adding a second DMM to your testing setup for doing current, but that curve looks roughly correct. Remember, as voltage drops, less current will be pulled from the batteries.

I'm amazed they recovered so well.

 

[Hallmcc]

Thank you Chrontius.

I have already purchased two new DMM.
I am shocked with these batteries as well.
So far they are working great.

 

[^Gurthang]

Hall,

Your thread is why I love CPF. I just salvaged an 8 cell Dell pack. I've got pairs of cells w/ similar readings. I was going to toss the low V cells, now I'll [carefully] charge them up and see if they hold up. Even if they drop off faster than a new cell when in use, I'm cool w/ that cos I've got $0 invested. Great thread, thanks for the info.

^G

 

[Fallingwater]

RE opening batteries: it's very possible to open even glued-together ones without ripping them enough that they become impossible to reassemble correctly. See here for an example on the battery of an EeePC 701 (mine, to be precise :p ).

As for cells that are brought back from death: my experience is that they often have fairly quick to insanely quick self-discharge. The worst I tried, from a laptop pack that had been dead for a long time (zero recoverable cells out of eight), went from roughtly 4.18V to zero in less than 24 hours.