Extracting 18650 from battery pack

Batteries and Chargers Rechargeable Batteries
1

Hello the forum. A friend gave me a "spent: battery pack from

his (I believe) a Stromer electric bicycle. I understand he was not

good at keeping his battery packs charged. It seems that when

this brand battery pack goes to low of voltage, it shuts off permanente.

The system will now longer charge it!. I guess that is different than

a protected cell 18650. you just recharge to get it going. I have had

it a few years as is.

Photos show 5 cells parallel, 10 sets in series. I have not tried to

take off the tabs, spot welded?? Is it easy to do, or might I screw up

the 18650s? I probably should measure each parallel set to see

where they are at. Any comments appreciated.

Stan.

Well, now need to learn how to post photos here. Ops.

2

Any parallel set that’s at 0 is pretty much garbage, but other sets might be salvaged.

Even if spot-welded, that’s no big deal. Pry off the tabs, grab and pull off the sharp pointy parts with needlenose pliers as best you can, file down what’s left.

I’m assuming those are nekkid cells and all the “protection” is in the BMS, and there’re no protection boards on individual cells, right?

Anyhoo, once cells are separated, run ’em through an analysing charger for actual capacity vs what’s on the tin, to see how good/bad they might be. Also several quick IR tests for internal resistance. Then top ’em off (default state after analysis) and let ’em sit a coupla weeks, see if they maintain their voltage or if you end up with little electron puddles around ’em if they leak.

Good voltage, no puddles, they’re fine for use in low-stress lights.

3

Oh yeh, I still got a bunch of old-timey panny-As that I’m still using in headlamps and stuff.

4

New batteries are $5. Is it really worth the risk and time?

5

Absolutely.

6

I’ve done a couple of Sony VAIO packs from 2004ish and got 16 2002 dated 2000ish mAh cells that are still at ~75%.

I also got 4 Samsung ~2200mAh cells out of an older HP pack that are useable.

Chris

7

There is a risk, I tried removing a 18650 from a vape pen that was given to me. In the process, the battery shorted, took off like a rocket across ,my shop, made a huge cloud of probably toxic smoke, nearly burned me and my shop up. So, yeah, probably not worth it.

8

I measured the parallel banks, all 10 are 1.1 to 1.2V. Each bank has a sense wire for voltage.
No 0v banks.

Imgur
Imgur

9

Li-on below 2.0v for a protracted period of time is permanently damaged.
You got an abused pack, and [I have had it a few years as is.]

That has gone way way to long. I’m a believer in reclaiming useful cells, and have, but those are only good for recycle at this point.

10

Thanks for the responses. It has gone too low too long. Won’t
waste my time and energy.

Stan.

11

Know any Ukrainian guys? You could put the cells through all sorts of torture tests to see how they react. Drive a nail through one, squish one in a vise, chainsaw another one, etc.

Just be sure to wear all the appropriate safety gear (shop glasses, flipflops, shorts, etc.).

12

Probably a good idea to just recycle them.

I pulled some batteries out of an old laptop many years ago and the voltage was really low. But I thought I would try to charge them and see how they go. I was certainly concerned about them and kept an eye on them while they charged outside. They did not get too hot and charged normally. I did a capacity test and they are around 1,900 mAh. And the voltage stays up in the 4.1 or higher range after many months of storage which is a good sign of battery health. I was surprised as to how well they turned out.

But like others have said, new batteries are not that expensive so probably not worth the risk. And with the batteries I salvaged, I don’t have a need for them since I buy higher capacity batteries for my flashlights. So they just stay in my storage container.