1

Hi,

recently I salvaged a cracked laptop battery pack. As only the plastic case was cracked, batteries were intact. This yielded six 2550mAh panasonic 18650s, however they were welded together using metal tape. After removing most of the metal tape with pliers, there are still some rough spots on both ends of the batteries, where this tape was previously spot-welded.

How do you smooth out these spots? I was thinking about either using a file, or a grinding stone, but lets see how you did it.

2

I use a Dremel with whatever grinding or cutting bit I have at hand.

3

Good tip, too bad I dont have one :smiley:

Guess an angle grinder or belt sander would be too much… so I probably stick to that grinding stone.

4

Stop in Harbor Freight if you have one nearby. They have cheap knock off dremel type tools for about $10 that come with a handful of bits. They are nothing high powered or high quality but they should do a nice job on something that isn’t too demanding of it. I have used it to successfully grind down some pocket clips and clean up salvaged cells in the past. It made easy quick work of it.

5

The angle grinder would be a bit dodgy, but I reckon if you clamp the belt sander in a vice upside down , and touch the batteries gently against the curve at the edge, you should get great results.

6

Another good tip! Now that I recall, my belt grinder actually has some clamps included for this upside-down action! Will give it a try with fine sanding belt, that should clean it well :beer:

7

The sanding belt should be narrow enough not to exceed the width of the flat top, otherwise it will scrape off the plastic insulator too.

Also, if it’s narrow enough, it should also be at at angle just to hit the spot welds.

Your best bet is a small grinding stone that can only grind out the protruding spot weld leftovers.

8

I find that if you break the tab off and leave a small square part of it on the top or bottom of the cel you can then just use something like a nut pick to smooth the edge of it and knock down that tiny sharper edge so it lays perfectly flat and doesn’t bother a thing . you just have to be a little extra careful when working /flexing the tab back and forth when breaking them .if you’re just trying to jerk or tear the ttabs off sometimes you can really deform the bottom of the cell .it’s faster to do it my way…Plus I have decided to do minimal work on cells till I know if they have any value . they go into the charger these days with very minimal time or effort invested in them because spending time dressing up cells that you end up pitching is pretty silly .
I do mine by hand which is fairly time comsuming and use small files ,old micro shears that are already abused and on the tops I’ve taken the one side and locked it in under the vent hole and then just cut the spot weld off.I’ve heard people using a sharp blade like a box cutter to slice off the spot welds .
you can leave them and just knock down the edgy edge on them …and on the tops just leave them and add a solder blob on top of them …

try to just leave the broken of tab and then run a hard piece of metal across the edges .it’s very quick and easy

9

I also try to leave a square and whatever sticks out I just push it down flat.
Does anyone else just enjoy salvaging cells a little too much?
What do you do when you have 100+ cells and dont know what to do with them?

10

have a sale of 10 cells each?

11

I use a Proxxon rotary tool (similar to dremel) and these drum sanding bits. They are not as aggressive as a grinding wheel and makes a smoother finish.
https://www.amazon.com/McKay-Abrasive-Sanding-Rotary-Tools/dp/B01E7P3Y2Y

12

I might just do that. I actually tested for capacity and wrote on the cell itself. Then I realized i dont really want to go through all the trouble of making an e bike battery pack.

13

Just take a small jeweler’s file or something, and just get the sharp bits off. Then you can use those flat-tops as button-tops. :smiley:

14

Hi.
II use a flat diamond file. top and bottom.
Then solder a blob on top to cover and raise it for better contact.
I got LG and Samsung cells out of my two. (2200’s)

15

I prefer to just buy new batteries, but we had an old laptop that didn’t work anymore so I thought I would try to salvage the batteries.

I used a Dremel with a small grinding attachment to remove the welding spots. Then I taped a piece of fine sandpaper to a pencil eraser and attached it to the Dremel to further smooth out the the battery terminals. I didn’t want to have these “free” batteries cause unnecessary wear on my flashlight springs.

I measured 1,900 mAh, so not the best, but adequate for my Convoy UV flashlight that doesn’t get used much. And they keep their voltage near 4.2 for a long time so they seem to still be good.

The battery terminals are very smooth despite how the pics may look.

16

I just try to get the sharp pointy bits flat and call it good. Used “salvage” cells for quite a while exclusively. I say salvage loosely because I bought the packs at HD new just to take the cells out. Never had a problem with a little bit of extra spot welded connector left.

I would make sure the neg side had nothing sticking up, then the pos side I would work with a pair of needle nose pliers to try and get as much off as I could