harvesting 18650s from laptop pack?

I just pulled 6 18650s from an older Thinkpad battery. The computer would shut down immediately upon disconnecting AC power so I assumed that it had some bad cells but 4 of the cells tested at 4.14v and the remaining 2 tested at 4.13v. Any idea why it would no longer run the computer? Failure of the pack's electronics maybe?

Anyhow, I'm hoping somebody here can help me ID the cells so I'll know the rated capacity and maybe offer some advice on how to test them to determine if they're safe to use. The shrink wrap on the cells is red and semi-transparent and they're labeled with a "C", "DLGPE4", and another number that's different for each cell (ex. "0050710").

Thanks,
Tony

Certain computers have a date ID built into the battery pack. Dell for example wanted to allievate accidents such as laptop fires due to cell imbalances and what not, and certain models actually refuse batteries over a certain age. I'm not sure how it works.

hey there,

I have a bunch of personal experience on using laptop 18650s, because I'd used to take the battery packs of all the laptops thrown away at my high school. plenty of 18650s around.

the specific cells you're referring to are probably extremely old.
all of mine didnt hold a charge well, and performed poorly under most current drains. I just tossed mine out and kept 2 for pictures if ever needed. aha! photo op!

these look familiar? the number is probably some sort of production/date code.
in my case, these came from a 10 year old ibm laptop. dont remember the model.

Illum,
Thanks, I had no idea about that.

csshih,

Yep, that's them.:thumbsup: I'd say you're right about them being extremely old. I don't know the exact specs on the laptop without looking but the processor is somewhere around 400 mhz if that helps date it. I'm running a discharge test on one of the cells now just to see what the capacity is like compared to a relatively new 2400 Ultrafire. I'm not expecting much, but if they'll run the light for awhile, I may charge them up outside and store them for use in an emergency.

Hi Tony,

just keep in mind that any 18650 you yank from a pack like that will be unprotected once removed. If you do any sort of discharge test, you will need to make sure that the device you are using is incapable of over-discharging the cells.

mdocod said:

Hi Tony,

just keep in mind that any 18650 you yank from a pack like that will be unprotected once removed. If you do any sort of discharge test, you will need to make sure that the device you are using is incapable of over-discharging the cells.

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Thanks!
That reminds me... How "set in stone" is the 3.5v open circuit rule for full discharge? The drop-in in my light will shut off when the voltage gets low but it's more like 3.24v open circuit if I check the cell immediately after the light shuts off. This has only happened once and I had the cell in the charger within seconds and back above 3.5v very quickly (it might have even rested back to 3.5v but I didn't want to let it sit discharged long enough to find out).

You could always get an L-mini II, which switches to low mode when the battery becomes low, and finally shuts off at a certain cutoff point. I have been using unprotected laptop cells in mine, and they work fine.
I have also dissembled over a half dozen battery packs, but a lot of the time they don't yield many good cells. Also, they are very hard to open, especially without damaging any cells.

Illum said:

Certain computers have a date ID built into the battery pack. Dell for example wanted to allievate accidents such as laptop fires due to cell imbalances and what not, and certain models actually refuse batteries over a certain age. I'm not sure how it works.

Click to expand...

Very true about Dell's packs. I recently harvested 6 18650 cells from a pack that would only run the laptop a few minutes after the AC was unplugged. All six cells where fine and they power my Pilot Whale for almost 2 hours (same as the Wolf-eyes cells that came with the light.)

I rarely even used the laptop on the batteries but it was 2 years old. I replaced the pack with the newer 9 cell pack and everything is good again.

FYI: the inside of the Dell pack was marked "Sony" and the cell are bright green.

i have a ton of 18650's taken out of Dell battery packs. I use them in my P7 Mag. :thumbsup:

Mjolnir said:

You could always get an L-mini II, which switches to low mode when the battery becomes low, and finally shuts off at a certain cutoff point. I have been using unprotected laptop cells in mine, and they work fine.
I have also dissembled over a half dozen battery packs, but a lot of the time they don't yield many good cells. Also, they are very hard to open, especially without damaging any cells.

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I must say I like the L-Mini II! It's only a pocket clip away from something I'd consider a perfect EDC.

I really wish I had some way to measure the voltage under load when mine cuts off. It may be that it cuts off at the right voltage and I just didn't allow the cell enough time to come back up to 3.5v after removing the load. Running a discharge test, I usually allow 5 minutes for the cell to rest after removing the load before checking the voltage but when the light shut off it made me a little nervous so I checked immediately and quickly threw the cell on the charger when I saw it was below 3.5v.

Interesting result (or maybe not) on the discharge test. The old laptop cell that I tested will actually run the light longer than the newer Ultrafire cell but with a lower current measured at the tail. At the 2 hr mark where the Ultrafire had discharged to the point that the drop-in shut off, the laptop cell was still at 3.77v open circuit. Difference in internal resistance maybe?

I have pulled those red cells out of more recent Lenovo packs. I haven't really tested them thoroughly, outside of voltage and current. I think they are made by Sanyo. Mine are serviceable when delivering currents under ~1.4A. They can't fully power an MC-E or P7 though.

Tony Hanna said:

Interesting result (or maybe not) on the discharge test. The old laptop cell that I tested will actually run the light longer than the newer Ultrafire cell but with a lower current measured at the tail. At the 2 hr mark where the Ultrafire had discharged to the point that the drop-in shut off, the laptop cell was still at 3.77v open circuit. Difference in internal resistance maybe?

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Not surprising. The true capacity of the older laptop cells is probably lower, but you are, in effect, taking advantage of the effect of aging on li-ion in that direct drive application. As li-ion cells age, they suffer from increased internal resistance and a loss of voltage maintenance (reaction speed). If the cell still holds above 4.0V after a charge for a few days resting then it is probably perfectly safe to use provided that you are using a charger that won't over-charge it, and either you or your flashlight step in to keep the cell from being over-discharged.

I have 9 Panasonic 1800mAh batteries removed from an 8 years old DELL Inspiron 5000e and any one of those can deliver 1900mA to a direct driven SSC P7. There is some internal resistance but still work fine.

These should be fine for what I've got in mind then. Initially I just wanted to keep them around for spares to use in the L2 in an emergency but I got bored earlier today and made a spacer tube for a plastic 2x D Garrity that I got out of a clearance bin at an auto parts store for $0.25. A kpr113 running off of 2x 18650s is pretty interesting. I'm waiting for it to go but it's hanging in there so far.:thumbsup: