Green laptop batteries

[alantch]

I cracked opened a laptop battery pack and found 6 pcs of batteries in there in what looked like they're 18650 batteries but I can't be sure. The letterings on the batts are "SF US18650GR" and "T G7111NL21W". Does anybody here know the details for these batteries - like what's the mah, voltage, whether they're protected or not and whether they're safe to use in lights that accept them? If they can be used, can I use the Ultrafire WF-139 from AW to charge them?

Don't wanna have 1 blow up in my face in the course of charging/using them without knowing what they really are. Thanks.

 

[SilverFox]

Hello Alantch,

I believe those are Sony 2400 mAh cells. They are unprotected.

The recommended charge rate is in the 1500 - 2000 mA range and the maximum charge voltage is 4.2 volts. The maximum charge rate is 2400 mA.

The recommended charging involves charging at a constant current until the cell reaches 4.2 volts, then holding the voltage constant as the current drops off. The charge is terminated when the current drops below 100 mA.

I am not sure if the WF-139 follows this algorithm, but a lot of people use it to successfully charge their Li-ion cells.

Tom

 

[Mercaptan]

My (now defunct) Dell Inspiron 9100 battery pack has 2000 mAh 18650 cells, but they are welded to an internal frame at the terminals. I have no idea how people can separate these things, unless they really bash 'em.

 

[FredM]

How do you safely open the actual pack? Mine seems to be plastic and no screws or anything. I have 2 6 cells from my now broken Thinjpad X40.

 

[alantch]

Thanks for the info SilverFox, much appreciated. I'll try and charge them and we'll see what happens. I googled on the number and several capacities came up ranging from 1400mah to 2400. How can I tell their capacity for sure?

FredM, I twisted the pack until the 2 halves came apart a bit, then I pried them open with a flat screwdriver. Easy.

In the interest to keep this as a reference, these are how the cells look like.

(+) terminal

(-) terminal

 

[SilverFox]

Hello Alantch,

I happen to have some of those and they were sold as being 2400 mAh. When I tested them, they came in close to 2300 mAh, so the rating seems to be about right.

To tell for sure, you need to do a discharge capacity test on them. If you have a light that you know the current draw of, you can get a pretty good idea by doing a runtime test with it. Milliamps of current draw times hours of runtime will give you mAh of capacity.

Tom