18650 battery pack - How to remove (thick) nickel strip?

[maarten_almighty]

I am trying to find a good way to remove (quite thick/strong welds) nickel strip from 18650 battery packs without damaging the 18650 cells...and having a relatively flat surface (on the cell's terminals) in order to be able to properly weld on new nickel strip in the future.

It's a waste to damage/destroy perfectly working cells and I would love to hear any tips/tricks from the people more experienced than me with battery disassembling/building.

The nickel strip on the battery packs I have is approx 0.3mm thick and is nickel-coated steel strip. It is welded 4 times per cell per side (2 weld operations, 4 indents from the spot welding pins). The diameter of the indents is approximately 1mm or perhaps 0.8mm.

My current approach:

1) Use tiny cutting pliers to cut free a single cell on the negative side of the parallel group

The pliers look like these:

I cut the nickel strip (on the negative side of the cell to prevent shoulder shorting the cell whilst cutting) along the lines indicated in green in the following image:

2) After having cut loose the negative side I wiggle the cell back and forth until the spot welds on the cell's positive terminal release.

Here is an image of one of the parallel packs after having removed a single cell this way:

3) Pull off the nickel strip by grabbing a loose bit with the same tiny cutting pliers and wiggling it around. This usually does get the nickel strip off eventually but usually I end up either pulling too hard on the housing which creates 'bumps' on the housing where it has been deformed (on the spots where the strip was previously spot-welded), and in the worst case which happens quite often in my experience a hole is created in the casing when trying to remove the nickel strip (and that 18650 cell has become useless), photo examples:

This method has worked great for me for other battery packs (for example for laptops where they use a lot thinner nickel strip and weaker welds in my experience) but for these strong welds/thick strip it almost always causes some sort of damage to the cells

Questions:

What could I improve/skip/do different to prevent this cell damage?
What is wrong about my approach?
Do you have any tips/best practices/methods to remove thick nickel strip from batteries with the
least amount of damage to the cells?

Thoughts:

I thought I could perhaps use a rubber or wood hammer to hammer back the deformed spots on the battery after having removed the strips but obviously it would be much better/safer to find a way of removal which doesn't (or does so but to a way lesser extent) damage the cells. Update: I tried this and it worked quite well (as I managed to push back the deformations/make the battery flat again) even though there were still some 'deeper spots' in the battery where part of the casing material had been pulled away whilst pulling off the nickel strip.

I thought about perhaps grinding off nickel strip off of the negative battery terminal using a bench grinder or dremel for example. This way I run less risk of deforming the battery housing since I don't pull on the nickel strip after removing the battery from the pack itself. If I make a 'battery grinding jig' (plastic tube as battery guide with a grinding wheel placed behind it, which will be perfectly parallel (or as close as possible) to the battery terminal face. With careful grinding this shouldn't damage the battery housing itself apart from removing the nickel coating/roughing up the surface.

I'd then do the same to the battery positive terminal (first hammer in the dents, then grind it flat).

However this method leaves me with a part of the battery casing which has no nickel plating so will be prone to rusting in the future which is a big disadvantage. I could perhaps dip the battery in some sort of resin afterwards but this is not a great option IMO...

I could perhaps use some sort of conductive paint afterwards to cover the battery terminals (after grinding) to prevent rust but I'm pretty sure I won't be able to spot weld after having applied such type of paint to the terminals, and I've been told this type of paint is quite expensive. i could alternatively store the batteries dry/inside before they are in a new battery pack and once they are welded into a new pack I dip the pack in paint or silicone or something similar to seal it... Any other suggestions /better suggestions regarding this issue would also be greatly appreciated.

Thank you very much!

 

[john61ct]

Leave them on as tabs and in future weld to the tabs

 

[goatman]

grinding makes the metal hot, might as well solder them so if you don't want the heat I wouldn't grind. like john said leave the tabs on but that makes hard to separate the cells. what I would do is spin the nickel off the positive ends, grab an end of the strip and roll it off. I don't know if you've seen how you open a can of Spam, like that.

then leave the nickel on the negative end and use your cutters to separate the cells. you can use a dremel on the positive end to get rid of the spot welds, the positive can take a little heat from grinding but keep the positive end up, heat rises. I solder my cells so I really don't worry too much about heat like others do, soldering is a quick hot heat/ 2 seconds

I wouldn't be whacking the cells with anything to get rid of dents

I usually just pull all the strip off without issues but I did a bunch of Panasonic 18650pd and I lost 12 cells pulling the negative strip off because of holes and the deformation was bad and I was being real gentle, it seems like a softer/weaker metal than a 25r, a 25r I just rip and tare off the nickel with no problems.

as far as painting, I just spray my batteries with plasti dip. it electrically insulates and waterproofs the battery ends and peels off clean. I used to pour the plasti dip on from the can but that's a pain and takes too long and the fumes will get you wasted, bad stuff. ill spray a good coat on then grab a hair dryer on high for a minute and recoat/ 3 or 4 coats. 15 minutes the batteries done and you don't get stoned.

 

[999zip999]

What do you plan on doing with this battery pack ?

 

[maarten_almighty]

@999zip999 I was originally planning on separating all the cells, stacking them in a more compact way (such that I can fit more cells in the same space) and building a new battery pack for my ebike with them.

 

[BretCahill]

I find all kinds of batteries next to the highway and almost all survive the 100+ km/hr crash.

The cell or flashlight is often destroyed -- motorists pull over in an emergency then leave them on the roof, wheel well, etc. along with the tools then drive off -- but the battery is still good.

Just charge and discharge outdoors a few times before bringing anything indoors.

My original 11 [nominal] amp hour is down to 4 amp hours. BMZ just admitted their old batteries only last 4 years. Not willing to pay $1100 for a new [8 real amp hour] battery I'm unplugging the BMS then keeping as much of the old Ni tab as possible keeping track of the wire order. I plan to spot weld the old tabs to a new cell assembly.

I don't mind if a few old 1amp hr cells get destroyed. I just want to preserve the old nickel strips.

 

[BretCahill]

I find all kinds of batteries next to the highway and almost all survive the 100+ km/hr crash.

The cell or flashlight is often destroyed -- motorists pull over in an emergency then leave them on the roof, wheel well, etc. along with the tools then drive off -- but the battery is still good.

Just charge and discharge outdoors a few times before bringing anything indoors.

My original 11 [nominal] amp hour is down to 4 amp hours. BMZ just admitted their old batteries only last 4 years. Not willing to pay $1100 for a new [8 real amp hour] battery I'm unplugging the BMS then keeping as much of the old Ni tab as possible keeping track of the wire order. I plan to spot weld the old tabs to a new cell assembly.

I don't mind if a few old 1amp hr cells get destroyed. I just want to preserve the old nickel strips.