How to Prevent Sparks While Salvaging 18650 Cells From Old Battery Packs?

[108CAM]

I have some battery packs from cordless vacuum cleaners and I want to salvage the 18650 cells from them.
Last night I was dismantling a 24v battery pack with 6 18650 cells that I wanted to salvage.
After removing the circuit board, I tried to seperate the 2 plastic parts that clip together and hold the cells in place but realised that the metal tabs used to join the cells together were preventing me from doing so. I then started to cut the tabs and when I was doing it, my cutters were touching against the cells and tabs adjacent to where I was cutting. This created a momentary short circuit and some sparks.

I then looked at YouTube for videos on containing tips on how to salvage 18650 cells from battery packs without the sparks (and the jumpscares that result from them) but couldn't find anything.

Does anyone here have any useful tips on what I can do to avoid these sparks and a potential short? I know that a few tiny sparks won't cause any harm but I really need some tips on how I can salvage the cells without destroying them and constantly scaring myself in the process.

[IanB]

Be more careful? I mean seriously, just how clumsy are you? 

[ejeffrey]

Put masking tape over the metal you don't want to touch?  Or on your tools?

[108CAM]

Be more careful? I mean seriously, just how clumsy are you? 

I'm not clumsy at all. I was being as careful as I could but still got the sparks. I just need a way to cut the tabs that are welded onto the ends of the cells to create the series circuit.
No matter how or where I cut the tabs, I always get some kind of spark and I want to avoid this because it gives me a fright as I don't know when it will happen or how big the spark will be.
I'm currently left with a half cut battery pack that's holding it's cells hostage in a plastic shell.

[108CAM]

Put masking tape over the metal you don't want to touch?  Or on your tools?

Good tip. I'll give it a shot and this time I'll do it outside where it's safer

[108CAM]

This is the pack I'm trying to dismantle. I managed to cut one of the tabs on Side 1 without issue by using the masking tape trick but when I moved to the diagonal tab, I got sparks despite having masking tape on the 5 cells I wasn't touching.
Can someone please tell me what I'm doing wrong? I don't know what else to do or how to dismantle this thing without blowing it up
I was thinking of cutting the tabs in the order of the series string that the cells are in but still want a method that will prevent the sparks

Side 1


Side 2

[IanB]

Well, hint number 1 is always to discharge a lithium battery pack before attempting to disassemble it. No charge, no current, no sparks.

But what did you do to make such a mess of the tab in the picture? It looks completely mangled.

Do you have a Dremel with a cut-off wheel? You could just neatly and carefully cut through each tab without touching anything except the tab.

[108CAM]

Well, hint number 1 is always to discharge a lithium battery pack before attempting to disassemble it. No charge, no current, no sparks.

But what did you do to make such a mess of tab in the picture? It looks completely mangled.

Do you have a Dremel with a cut-off wheel? You could just neatly and carefully cut through each tab without touching anything except the tab.

I don't have a Dremel and don't know how to discharge the batteries safely. I was using a pair of small side cutters. It's the only tool I have with a head that will reach the tabs. Everything else is too big

[IanB]

Well in the top picture you seem to be trying to cut the tab in the lower middle of the six cells. You have to remember that the centre of the cell where the tab is attached on this cell is the opposite polarity of the outer case. So when you try to reach in with the side rippers, you are likely to make a short between the center and the outside. Why not instead try to cut on the top right cell, where the tab is attached to the case and there is no danger of a short?

[108CAM]

Well in the top picture you seem to be trying to cut the tab in the lower middle of the six cells. You have to remember that the centre of the cell where the tab is attached on this cell is the opposite polarity of the outer case. So when you try to reach in with the side rippers, you are likely to make a short between the center and the outside. Why not instead try to cut on the top right cell, where the tab is attached to the case and there is no danger of a short?

Just tried that and it popped right off with no sparks. The next question is how to remove the other end of the tab without shorting the cell it's connected to
I'm assuming I should cut the tabs on the other side by snipping the negative ends like I did before

[IanB]

Just tried that and it popped right off with no sparks. The next question is how to remove the other end of the tab without shorting the cell it's connected to

You don't need to. You only need to detach one end of each tab and then the cells will come apart. Once the cells are separated you can bend the tabs and cut them off without any difficulty.

[108CAM]

Just tried that and it popped right off with no sparks. The next question is how to remove the other end of the tab without shorting the cell it's connected to

You don't need to. You only need to detach one end of each tab and then the cells will come apart. Once the cells are separated you can bend the tabs and cut them off without any difficulty.

Ian, I can't thank you enough for all the help you've given me.    :-
I've just finished removing the remaining tabs by cutting them where they connected to a negative battery terminal and then I pried apart the plastic housing and the cells were free!
Your tip with cutting the tabs at the negative ends has saved the day and I will be sure to remember it for my next 18650 salvage.

All I need to do now is remove what's left of the tabs and then I can test the voltages.
One more question, am I safe to use the side cutter to remove the tabs from the positive ends now that the cells aren't in a circuit anymore?

[IanB]

One more question, am I safe to use the side cutter to remove the tabs from the positive ends now that the cells aren't in a circuit anymore?

No, you're not safe, you still have to use care not to make a short between the positive and negative side of the cell. There is some insulation provided by the plastic sleeve, but it is not that thick and you can punch through it if you are not careful.

[108CAM]

Good News
I've got the cells all cleaned up and removed the remaining bits of tabs

Thanks to everyone for their help and tips. This wouldn't have been possible without you!
I also did a voltage check and all 6 cells came up at 3.6v which is awesome considering an 18650 is 3.7v so they've only dropped a tiny bit!

[amyk]

3.6V resting voltage is around 40% charged, a good storage voltage.

If I were you I'd probably try to drill out the welds on the + terminals (the side with the small black insulator rings) first, or at least weaken them enough to pry the tabs off.

[BeBuLamar]

Well, hint number 1 is always to discharge a lithium battery pack before attempting to disassemble it. No charge, no current, no sparks.

But what did you do to make such a mess of tab in the picture? It looks completely mangled.

Do you have a Dremel with a cut-off wheel? You could just neatly and carefully cut through each tab without touching anything except the tab.

I don't have a Dremel and don't know how to discharge the batteries safely. I was using a pair of small side cutters. It's the only tool I have with a head that will reach the tabs. Everything else is too big

You do not want to discharge the battery to preven spark. You have to discharge them very low and you would damage them that way. If it's the battery in the picture I don't see it's that difficult.

[IanB]

If I were you I'd probably try to drill out the welds on the + terminals (the side with the small black insulator rings) first, or at least weaken them enough to pry the tabs off.

I don't think you want to advise the OP to take a drill to a battery. There is a risk of drilling right through the cap and creating an internal short between the electrodes.

[108CAM]

If I were you I'd probably try to drill out the welds on the + terminals (the side with the small black insulator rings) first, or at least weaken them enough to pry the tabs off.

I don't think you want to advise the OP to take a drill to a battery. There is a risk of drilling right through the cap and creating an internal short between the electrodes.

I wouldn't go drilling a battery either. One small slip could cause a big mishap. I used side cutters to carefully pull the tabs off the cells.

[Mechatrommer]

Well, hint number 1 is always to discharge a lithium battery pack before attempting to disassemble it. No charge, no current, no sparks.

discharge to what level? below 2.4V is a good way to kill a li-ion battery https://www.instructables.com/How-to-Prolong-the-Life-of-an-18650-Battery/ recommended minimum discharge level is about 3V, use proper Li-Ion discharger is paramount, or self monitor with DMM while discharging at not more than its discharge (C) rate. so at safe minimum discharged voltage, you still can have slight spark... or the risk of discharging them further to the damaged level.

btw it is sad to see OP slaughtered all the metal connectors to the total lost.. there need some careful peeling and twisting art from the edge, center and inside of the connectors using angled side cutter, my best tool is now unobtanium Lindstrom 575EI, but any cheap china side cutter with sharp/small/pointy/flush tip will do (pictured below), unlike what the OP used, that is for blunt and heavy job. masking advice on "unwanted to be touched" metallic also recommended for noob. attached below was a job of replacing 6x18650 cordless vaccum unit early this year, similar series and locked to the retaining plastic configuration, just different geometry... the tear points only on the very spot welded points, so i can flatten and reuse the metal connectors by soldering back to new batteries set (pink, old batteries = brown).. instead of making another bodge wires that may not fit in the space tight enclosure of the vaccum unit... fwiw...

[108CAM]

Well, hint number 1 is always to discharge a lithium battery pack before attempting to disassemble it. No charge, no current, no sparks.

btw it is sad to see OP slaughtered all the metal connectors to the total lost.. there need some careful peeling and twisting art from the edge, center and inside of the connectors using angled side cutter, my best tool is now unobtanium Lindstrom 575EI, but any cheap china side cutter with sharp/small/pointy/flush tip will do (pictured below), unlike what the OP used, that is for blunt and heavy job. masking advice on "unwanted to be touched" metallic also recommended for noob. attached below was a job of replacing 6x18650 cordless vaccum unit early this year, similar series and locked to the retaining plastic configuration, just different geometry... the tear points only on the very spot welded points, so I can flatten and reuse the metal connectors by soldering back to new batteries set (pink, old batteries = brown).. instead of making another bodge wires that may not fit in the space tight enclosure of the vacuum unit... fwiw...

I was never planning to rebuild the battery pack or reuse the metal connectors. I don't even have the vacuum that the pack came from.
I just wanted to salvage the 18650's because I knew they were still good and may come in handy for a future project.
Also my side cutters are small and work perfectly for removing the tabs from 18650 cells. Below is a picture of an 18650 sitting between the handles of my side cutters as a size comparison.


BTW, I knew about the older thread, I just couldn't be bothered finding it

[108CAM]

January 2023 Update
I dismantled another 6 cell battery pack and using the knowledge gained from this thread, I was able to do it and only had one spark which was very brief.
All 6 cells tested at a healthy 3.7v and have been added to my pile.
Hopefully I can do the next one with zero sparks.
Once again, thanks for the help. These battery salvages wouldn't've be possible without you!

[Mechatrommer]

one of our local online seller doing just this for life. getting li-on batteries (tabbed/spot welded) from factory (reject/excess/grey market i'm not sure) and doing capacity test and specify the batteries on his own before selling them online. i bought from him several times including an XTAR VC2 charger (that can show battery mAH capacity while charging)

[EPAIII]

How to prevent sparks?

Know what you are doing!

[Terry Bites]

You dont want to be ripping at the welded tabs- you might rupture the cell housing. Nasty.

[108CAM]

Found another battery pack with 18650's inside. Hopefully I can get this one without any sparks.
I set that as my goal during the previous harvest but failed on the last cell.

[108CAM]

Found another battery pack with 18650's inside. Hopefully I can get this one without any sparks.
I set that as my goal during the previous harvest but failed on the last cell.

Well it was a case of Deja Vu with this harvest. A spark on the last battery.
At least I got seven more good quality Samsung INR18650-25R M cells to add to my pile of yet to be used 18650s.
Seems like cordless vacuum cleaners are an amazing source for good quality 18650 cells.