How to Salvage/Harvest Cells, Remove Old Welds

[YoshiMoshi]

Hi, I am trying to salvage some cells and looking for any tips. I'm seeing that I should "roll" old nickel strip off instead of pulling to avoid deforming the cell. When I do this I'm left with "nubs", little raised circular pieces of nickel that remain were the weld actually take place. What is the best tool to remove these little pieces? I would imagine some precision flush cutters? Any specific flush cutters made for this purpose that are great at doing this? Please provide like a part number and manufacturer I see people take a rotary tool and go at it, but wouldn't this be dangerous? Additionally, I'm worried that small nickel fragments will fall into the gap in the positive side, shorting out the cells.

Thanks for any techniques to remove the old nickel strips and cutting off the remnants of old Welds.

 

[bananu7]

A dremel with a small ball-ended diamond tool works very well to clean up the remaining nubs. You can hold the cell slightly upside-down to avoid the debris getting inside of it, and/or mask it with some tape.

 

[Zambam]

Never tried myself but end mills may work, giving a flush cut with a few twists by hand. I have an end mill of the right size somewhere. If I can find them I'll give it a try.

https://www.amazon.com/Cutter-Drill-Aluminum-Titanium-Straight/dp/B07PFT7PQS/ref=asc_df_B07PFT7PQS?mcid

 

[marka-ee]

I use a Dremel with a miniature cut-off wheel and slice through the nickel strips that way.For many salvage cells, I use them for other purposes, such as replacing cells in home appliances or lithium-powered stuff. So I leave some of the nickel strip on there to make it safer to solder to the ends of the cell because then the heat doesn't get into the cell much, it just stays in the nickel strip.

 

[harrisonpatm]

If you use a grinding method, you're essentially taking off the top layer of nickel from the cell. Which is its exterior layer/corrosion protection. So if you go that method, you end up putting the cell at risk for corrosion down the road.

Do the best you can with the "rolling" method and nickel strips, and don't stress about tiny leftover pieces. What project are you using them for, what cells are you harvesting?

 

[docw009]

I agree. If a cell will spend the rest of its life indoors with climate control, then the risk of corrosion is minimized and there's less downside with scratches in the nickel plating on the cans. Otherwise, if they go outside, those scratches will start rusting fast.

I used these inexpensive side cutters, available at the nearby cheap home builders store (Menards) for $3.99 USD. Great for rolling off nickel and also snipping it, They cost more on amazon.


It's irritating if you're a meticulous person, but it's better to just cut the strip off and weld over the remnants. You can also place the nickel strips over the nubs and weld around them. The .10 and .15 strips will conform. The better batteries use thick nickel that won;t roll off, but if you can rotate the strip around the welds, the nickel comes off easy with little effect.

I harvested name brand cells to build ebike batteries and I'm done with that. I'll buy new cells when they go on sale now. The re-cycled cells worked fine, but I'm more interested these days in smaller packs with high capacity 21700 cells.

 

[fechter]

I just smash the nubs down flat with the tip of a screwdriver, then weld over them.

 

[marka-ee]

If you use a grinding method, you're essentially taking off the top layer of nickel from the cell. Which is its exterior layer/corrosion protection. So if you go that method, you end up putting the cell at risk for corrosion down the road.

Do the best you can with the "rolling" method and nickel strips, and don't stress about tiny leftover pieces. What project are you using them for, what cells are you harvesting?

If you read carefully, I send I slice through the strips. I don't touch the actual cell.then the stubs of the remaining strips are easy to solder to.I don't have a strip welder, but instead have been sometimes using very low temperature solder. This with a quick dab of soldering iron at a high temperature is also safe to solder directly to the cell. I've never had a problem.Of course this is only good for making small battery packs for something like an electric drill or something like this.

 

[YoshiMoshi]

So is salvaging cells still worth it?

 

[gustavo88py]

I agree. If a cell will spend the rest of its life indoors with climate control, then the risk of corrosion is minimized and there's less downside with scratches in the nickel plating on the cans. Otherwise, if they go outside, those scratches will start rusting fast.

I used these inexpensive side cutters, available at the nearby cheap home builders store (Menards) for $3.99 USD. Great for rolling off nickel and also snipping it, They cost more on amazon.
View attachment 366632

It's irritating if you're a meticulous person, but it's better to just cut the strip off and weld over the remnants. You can also place the nickel strips over the nubs and weld around them. The .10 and .15 strips will conform. The better batteries use thick nickel that won;t roll off, but if you can rotate the strip around the welds, the nickel comes off easy with little effect.

I harvested name brand cells to build ebike batteries and I'm done with that. I'll buy new cells when they go on sale now. The re-cycled cells worked fine, but I'm more interested these days in smaller packs with high capacity 21700 cells.

an excellent tool for recovering cells

 

[harrisonpatm]

If you read carefully, I send I slice through the strips. I don't touch the actual cell.then the stubs of the remaining strips are easy to solder to.I don't have a strip welder, but instead have been sometimes using very low temperature solder.

You slice through the strips. Others, like @bananu7 in post #2, grind the nickel off the cells directly. I was simply offering my opinion to others who might be reading the thread.

So is salvaging cells still worth it?

That's up to the individual. You can read up on my two builds in my signature, both using salvage cells, and the massive amount of labor that went into retesting them to match them into a safe and high-performing pack.

 

[bananu7]

So is salvaging cells still worth it?

A lot of times the only thing wrong with salvaged cells is that they happened to be in a pack together with a bad cell. Such packs are discarded and scrapped in their entirety, and the cells sold for excellent prices. Considering you need to do manual labor on every cell to weld the pack together anyway, cleaning them isn't that big of a deal in the grand scheme of things.

As far as what I suggested - I admit I never really thought about corrosion when doing that myself, as it was mostly done for singular cells for home electronic devices. I think there might be some merit in using methods that preserve the original corrosion protection, or in protecting the cleaned area in some other way.

 

[marka-ee]

For me it's the satisfaction of recovering something that would have otherwise be probably thrown away. I like fixing my appliances or home electronics that were purposely designed to fail because of the fuse that slowly burns away, which is often the battery. Yes, it takes a lot of labor and it doesn't make sense for me if I look at it that way. I'll spend a couple of hours taking apart a battery pack, but for me, personally, it's worth it.

 

[docw009]

So is salvaging cells still worth it?

Might as well start with inexpensive cells. The first batteries I built were useless for ebiking, before I started using higher capacity, low IR cells.

If you can later find recycled cells with good quality and appropriate capacity then have at it, but they get harder to find. A year ago, a few of us got the nice deal on Molicell P45's. Built a 13S-1P that can sink 25A with ease. Those were wire banded too, so there was no nickel to remove.

Nonetheless, finding lightly used high capacity, high current cells is not a regular event. I'll wait for sales on new cells and lay in enough for a possible new project down the road. I just bought some new LG M50LT 5AH 15A 21700 cells for $1.99 each at 18650batterrystore.

 

[Barncat]

I used recycled cells for my first pack build, and the results were fine, but I'll never hassle with that again. Way too much labor, and you don't really know what your getting. The guys above have given you the salvage lowdown, but unless your budget is really tight- buy new from a reputable supplier. Known quality, and cells are all at matched voltage ready to build.

 

[harrisonpatm]

I used recycled cells for my first pack build, and the results were fine, but I'll never hassle with that again. Way too much labor, and you don't really know what your getting. The guys above have given you the salvage lowdown, but unless your budget is really tight- buy new from a reputable supplier. Known quality, and cells are all at matched voltage ready to build.

I completely agree with you. The only two cents I would like to add, is that it can be difficult to vet the reputable sellers. So if someone (like me) has the time, energy, resources and know-how to test and match cells themselves, you can get a much better result for less money. If you want to invest the time and effort, and it is quite a bit of time and effort. Your sentiment matches mine: I have three large-to-huge handmade packs under my belt, and while the results were great, I'm not sure I would be up for a fourth.

 

[gromike]

I'm more inclined to modify a surplus battery as a unit, rather than break it down to individual cells.
I have used several of these 36v packs with good results:

With this method the most time consuming part is encasing and mounting the battery. Breaking apart packs and cleaning and testing/charging cells makes it all too time consuming for me. At seventy plus years I have a need to conserve my time, as I seem to have an unlimited ability to add projects to my list.

 

[YoshiMoshi]

I have lots of old power tool packs from recycle center. But putting my multimeter on the battery pack to the plus and minus tabs, I get nearly 0 V. Seems like most of the recycled packs are like this. These packs are useless because the voltage is to low and way to long gone.

 

[harrisonpatm]

I have lots of old power tool packs from recycle center. But putting my multimeter on the battery pack to the plus and minus tabs, I get nearly 0 V. Seems like most of the recycled packs are like this. These packs are useless because the voltage is to low and way to long gone.

Power tool batteries tend to get abused and used the most. Finding appropriate sources for used cells is step 1.

 

[ScooterMan101]

A dremel with a small ball-ended diamond tool works very well to clean up the remaining nubs. You can hold the cell slightly upside-down to avoid the debris getting inside of it, and/or mask it with some tape.

+1 This is how I removed the nickel strips off a pack I had to disassemble . I also use a ring gasket of the positive side of each cell which helps with keeping debris out.

 

[ScooterMan101]

Might as well start with inexpensive cells. The first batteries I built were useless for ebiking, before I started using higher capacity, low IR cells.

If you can later find recycled cells with good quality and appropriate capacity then have at it, but they get harder to find. A year ago, a few of us got the nice deal on Molicell P45's. Built a 13S-1P that can sink 25A with ease. Those were wire banded too, so there was no nickel to remove.

Nonetheless, finding lightly used high capacity, high current cells is not a regular event. I'll wait for sales on new cells and lay in enough for a possible new project down the road. I just bought some new LG M50LT 5AH 15A 21700 cells for $1.99 each at 18650batterrystore.

I just went to 18650 battery store and they are no longer available . Sold Out . Darn , I would have gotten some.
I did notice though that they were rated at 7.3 amp continuous discharge so I would have had to do at least 4p packs to make them last.

 

[docw009]

I did notice though that they (LG ML50T) were rated at 7.3 amp continuous discharge so I would have had to do at least 4p packs to make them last.

That's true. I had bought them before, and they were rated at 3C then. Turns out that there is a temperature qualifier of room temperature for that current. So 7.3A it is.

I had the previous ones in a 3P, so a continuous 21 amps is 1000W. The bike it is used on will never sustain those power levels.

 

[docw009]

I have lots of old power tool packs from recycle center. But putting my multimeter on the battery pack to the plus and minus tabs, I get nearly 0 V. Seems like most of the recycled packs are like this. These packs are useless because the voltage is to low and way to long gone.

Are you measuring at the BMS output or behind it at the cells? A good BMS isolates the cells if they go below 3V/cell?

But with your other query about spontaneous combustion, maybe you want to minimize the risk and not pick up batteries from recycling centers,

 

[YoshiMoshi]

Are you measuring at the BMS output or behind it at the cells? A good BMS isolates the cells if they go below 3V/cell?

But with your other query about spontaneous combustion, maybe you want to minimize the risk and not pick up batteries from recycling centers,

Im measuring it at the BMS, without taking the pack apart. At the positive and negative terminals of the BMS

I see what your saying any idea which BMSs cut off cells once low?

 

[docw009]

Im measuring it at the BMS, without taking the pack apart. At the positive and negative terminals of the BMS

I see what your saying any idea which BMSs cut off cells once low?

Every last one of them. If you let the cells go under the minimum allowed voltages, and allow recharge, you have a inevitable fire for sure.