Taking a laptop battery apart - can I use these?

[Paul]

Inspired by this thread I opened an old laptop battery I had laying around. I expected a couple of 18650 batteries inside, but that wasn't the case (kind of silly to expect that when looking at the dimensions really). What I got was this:
(click for larger version)








I've measured the voltage of a single cell and it reads 1.2V. Doesn't tell much though, as the battery is pretty discharged. Now the cells seems to be connected two parallels with four in series. From the cover, the total voltage should be 14.8V. 14.8V / 4 = 3.7 V so the voltage should (could...) be the same as a 18650.
So, question is: Can I use these batteries for anything? Would it be safe to charge them with my 18650 charger?

 

[schmart]

These will be unprotected cells. In the laptop pack, the protection is handled by the circuit board at the bottom of your first photo. If you are measuring 1.2V on a cell, that is extremely discharged. (I'd expect that on one of the pairs, not just a single cell). Are all the cells this low?

On the laptop packs I have pulled apart, I have found that one of the pairs would be very low, while the other pairs were more in line with the expected safe range. I have assumed that the low voltage cells were kaput and why the overall pack failed. Hence, I discarded (recycled) those with very low voltages. The others I have safely charged and they seem to be holding voltage pretty well although I don't have anything to put them in to subject them to a load yet.

--Rick

 

[csshih]

what on earth are those?
do those individual packs have cells inside of them? then pack says Li-ion.. so it should be either those cylindrical li-ion cells or Li-pos.. but those packs are not flat. like lipos are.

1.2V.. that would be dead for liion -- probably not useful to revive them as they will have high internal resistance and not much capacity.


oh, and note: most macbooks use lipos now.

 

[jasonsmaglites]

im guessing you took apart the laptop battery since it was no good anymore. dead batteries just get thrown away, they dont work any better individually. i admire the diy spirit, as if it was 18650s you could have rebuilt it your self with some booty from dx :)

 

[Justin Case]

Prismatic cells.

 

[Paul]

im guessing you took apart the laptop battery since it was no good anymore. dead batteries just get thrown away, they dont work any better individually. i admire the diy spirit, as if it was 18650s you could have rebuilt it your self with some booty from dx :)

Actually the battery was working quite fine. Unfortunately the laptop got fried so I didn't have any use for the battery anymore.

They might not be the best batteries, but do you think it's a very, very bad idea to connect these to a charger and see what happens?

 

[Benson]

Actually the battery was working quite fine. Unfortunately the laptop got fried so I didn't have any use for the battery anymore.

They might not be the best batteries, but do you think it's a very, very bad idea to connect these to a charger and see what happens?

If you have a charger you don't mind risking and a concrete pad outdoors to run it on, you can safely hook up any battery to try and watch it explode. ;)

Without knowing how long the cells have been kept in this overdischarged state, the only way to know if they're still usable is to try them out.

There's definitely increased risk (vs. cells that had not been over-discharged) of problems during charging, but I wouldn't consider it a bad idea given suitable precautions. While a fireproof charging pit, as facetiously suggested, is a good start, monitoring the temperature while charging will actually allow you to catch a bad cell before it blows.

 

[Hack On Wheels]

On the laptop packs I have pulled apart, I have found that one of the pairs would be very low, while the other pairs were more in line with the expected safe range. I have assumed that the low voltage cells were kaput and why the overall pack failed. Hence, I discarded (recycled) those with very low voltages. The others I have safely charged and they seem to be holding voltage pretty well although I don't have anything to put them in to subject them to a load yet.

I just took a laptop battery apart on the weekend as well, and what you've said matches my experience quite well. It was a 9 cell pack, 3 sets of 3, wired in series. One set of cells all read ~2.3V, the next read ~3.0V, and the last read 3.5V.

I started charging with the 2.3V cells (under supervision); they spent a long time in the charger, as if they were resisting being charged. I finally pulled them off the charger as they just didn't seem to want to reach 4.2V. They didn't even get hot while charging, they were lukewarm for a while during charging but then they didn't seem warm at all when I finally stopped charging. Haven't charged the others yet, but 3V might be alright, and the 3.5V cells should be good to go.