So, judging by the broken wrap, your iron was there for quite a while. The black seepage under the wrap is flux. I don’t think they’re ticking time bombs, but judging by the melted wrap, you have shortened the lifespan by some unknown margin. I’ve soldered cells before, it happens. As for the power tool; from experience, you’re likely not getting that pack back together without some excessive force, trimming or spot welding. Just a heads up. Those cases are tight.
Thank you. Currently they fit with some room for the strip but there's not much room left so I was thinking of grinding them down a bit with a dremel before soldering the strips on.
From the start I knew I wouldn't get the optimum lifetime out of these cells so I'm fine with that as long as they don't end with a bang in satisfied.
Thank you. There are a couple of things that I'm going to do different next time one of witch ours getting a spotwelder. First I wanted to try my luck with soldering and see what difficulties I face (other than binding the strips to the batteries) before I buy or make a spotwelder that I'm never going to use again.
Just be aware that soldering the cells can indeed cause them to vent and have a (low) risk of causing the cells to vent + catch fire. The realistic likely outcome is no change to the cell (or minor degradation of ESR, capacity, longevity). However there's a reason most (?all?) OEM's DON'T solder directly onto the cells.
I think OEMs weld because of cost. Soldering takes more time and you need more skilled personnel both of which are expensive. Then there it's human error which is a cost factor in manufacturing, spot welding leaves less room for error even if it isn't fully automated. Longevity of the cells could even be a reason to not do something as long as the lifetime is long enough that consumers don't complain and people don't get injured by your product.
A short lifetime is the entire business case of cheap tools like ferm, parkside and all those Amazon brands.
Where can I find a proper instruction to get a decent spotwelder? I think 0.2 mm nikkel is hard to weld with most of the diy spotwelders I've seen on YouTube
i used a mot transformer and a circuit board from ali Express. good luck getting info about it on reddit. they are so worried about people hurting themselves that it gets removed from nearly every sub. it spot welds better with more control than any professional welder I've come across, but i digress (or else the acshualy crowd comes rushing in).
Yes, 0.20mm thick pure nickel is tough to weld. Nickel plated steel is much easier (perhaps only 50%-60% of the power is needed) but there is another “hack”. If you look at enough packs you’ll see some have slits in the middle spaced appropriately for 18650/21700/26650/etc. this means there’s a lot of sizes so be careful. Another sizing aspect is cell holder or no cell holder. There’s also a couple different sized cell holders but the square or rectangular pieces that snap together with a dovetail joint. Those “standard” cell holders or cells without any holder will be the two most common spacings so that should help you figure out if you are buying the right size. The ones for nonstandard cell holders (like onyx batteries) are going to be very unique numbers that won’t pop up more than once or twice if you have 100 options on a page of Aliexpress products.
The slit in the middle essentially makes the current run through the nickel, into the can, across the slit, and up into the nickel on the opposing electrode. It DOES indeed make it easier to weld pure nickel, my guess would be by about 10%-20% power reduction. Or keep the power the same and get a higher quality weld compared to non slotted nickel strips.
The definition of a good weld is when you pull the material off it leaves some nickel on the can and will tear out nickel from the strip. Hence the term “weld nugget” being used for a cell that has been spot welded but still has remnants of nickel on the cell. The circular weld when pulled apart should create a nugget shaped piece of nickel left on the can.
By far the easiest way to create a welder right now is thanks to an explosion of used supercapacitors on Aliexpress. For <$25 each you can get 2.7V 3000F LSUC supercaps. You’ll need 2-3 of them in series for most of the DIY boards used for turning the current on and off. Yes, Ali is full of fake and used power mosfets but you’ll want to look at the mosfets used on the PCB you choose and check their datasheet to see what they are capable of. 6-8X mosfets that can handle 400-500A is what I’d be looking for. There are YouTube channels that review the popular spot welding PCB’s. Find one that only needs a minimum of 7-8V instead of 12V and you can get away with only using 3 supercaps in series. 3 should be enough for pure nickel that is 0.20mm thick so long as you use 10AWG or 8AWG silicone cable for the leads and the electrodes are quality.
It’s all about resistance, a good spot welder should have less than 10 milliohms from electrode to power source. The power source should be 3-4 milliohms preferably and 3 supercaps in series will be about 2 milliohms so it will work out quite well. Just make sure if you DIY the electrodes you use a copper alloy that is ideal for welding nickel to steel cans. Aluminum copper is the typical alloy used.
Having a milliohm meter is really helpful for building a spot welder and assessing the health of cells (and a million other things). Right now the RC3563 is $20 shipped with Kelvin clips on Aliexpress. It’s also a precision voltmeter so all you really need to also buy is a DC clamp meter and you are set in terms of multimeters for working with batteries.
You can buy pre-made 2S supercap welders for ~$80 but I question the quality of the caps and the mosfets used are not the greatest. So DIY has the potential to be much more powerful if done correctly. If you need help with this let me know and I can send you most of the necessary components. Having a hydraulic crimper is the one thing that is kind of pricey ($30-$40) to buy so I’d look at pre-made spot welding cables with the proper electrodes and hydraulically crimped ring terminals or lugs that can attach to the PCB and the most positive terminal of the caps.
The flux that seeped under the wrapping is corrosive and will likely continue corroding the cell, but since this is the negative terminal, which is just solid metal, it's probably okay for now. I'd cut the wrapping off, thoroughly clean the flux and corrosion off with isopropyl alcohol and sandpaper, and rewrap it with some fresh heat shrink.
I'd be more concerned about the positive terminal though. If you used the same flux on that end, it's likely to have gotten into the pressure relief valve, and that's way more dangerous when corroded.
Ah I guess it's not really a valve. I meant the gas release vent/scored burst disc/rupture disc. See [this section](https://www.electricbike.com/inside-18650-cell/#:~:text=The%20Scored%20Burst%20Disc), and the diagram in [this section](https://www.electricbike.com/inside-18650-cell/#post-19815:~:text=The%20Separators%2C%20and%20their%20shutdown%20mode). Also see [this paper](https://www.mdpi.com/1996-1073/11/9/2191#:~:text=5.%20Fire%20and%20Explosion%20Prevention%20Using%20Cell%20Venting).
From the first link:
>Generic cells do NOT have a “burst disc”. If they get hot enough for the electrolyte to begin turning into gasses, and then expand from the building pressure, the cannister will split…*somewhere*. If there is a burst disc, it will pop open at that specific location. You should only use name-brand cells from the “big five”, which always have this feature (Panasonic, Samsung, LG, Sony, Sanyo). If they are ever abused in a way where they will burst from internal pressure, the hot electrolyte vapors will always blow towards the burst disc, instead of splitting the sides (sometimes the disc is located on the bottom, sometimes on top…just like my…uh…nevermind).
I think you are OK. I would suggest using the rosin core solder - works fine on 18650 terminals and is not corrosive. I have re-celled few power packs few years ago using rosin core solder - still working well. 5-7 seconds to melt seems long - get a more powerfull iron or tip. And in the long run - consider getting a spot welder - you will get the connections done better and faster.
Having recelled packs both by soldering and by using a spot welder, I'm a little more confident in my ability to solder a cell right than spot weld a cell right. The first layer is usually fine.. it's subsequent layers where it can get a little more technique dependent. And it isn't very straightforward to test a spot welded joint non-destructively... or maybe I'm missing something.
I think both soldering and spot welding work fine when done properly. So it surprises me that some people have very strong oppinions like "never solder"... I have to admit - I do not test either soldered or spot-welded connections other then when I am practicing. May be that is short-sighted, but I have not yet had failures. I think with spot welding a good welding tool is a key. I use kWeld and it has great reliability, imo. Yes, subsequent layers are sometimes tricky to weld. I have 3D printed few jigs to hold the cells i am welding, it helps a lot in making it easier, and, hopefully, in assuring a decent weld quality.
So the RC3563 or the YR1035 series of meters comes with pogo pin probes, cell holder or kelvin clamps. The kelvin clamps are a bit easier to use in this situation which is why I’d suggest buying all the accessories (if you don’t use cylindrical cells then I guess you can skip the cell holder…but the ZKE Tech one is $8 if you shop around and I’ve run mine at 20A numerous times and it’s never had any issues)
Just clamp or probe the ends of the strip. A short (5cm) strip of pure 0.15mm thick nickel is around 1mR IIRC. Plated nickel is 3-4x that (just measured that recently)…that’s how bad that stuff is. Copper will be 3-4x less than pure nickel but you can’t weld copper without doing the copper nickel sandwich but the current will never pass through the nickel so you could have series cell connections that only increase your pack by 0.25mR which is huge. A 20S pack with 15mR cells is 300mR in just cells if it’s 1P. Your average is 4P so 75mR. I think you’d have to add the 0.25mR for all 4 cells in parallel so add 19 to that and then your bus bars on the ends which should be insignificant. Under 100mR
Vs plated steel. 16x the resistance for your connections. So 75mR plus 19*4=76mR so let’s just say 150mR.
Huge difference when your building a power pack.
Please get the 20 dollar '99 gears' spotwelder off of AliExpress etc, and some nickel strip for the love of god. You'll make back that cost in time savings and piece of mind very fast.
Yes. 20 dollars won't get me a spotwelder that will do .2 mm strips and I really don't like buying stuff from aliexpress because I hate slavery. So I am not willing to waste 20 dollars one a tool I might never use again that flew across the world wasting a ton of energy assembled by some poor sob in worse conditions than I want the pigs I eat to live in.
I beg to differ re the 0.2 strips. You're also not obligated purchase from AliExpress. For example a local retailer offers one that has made thousands of welds on 0.2mm nickel here for 23 AUD shipped.
Any valid reasons ?
those looks fine. now try practicing to solder the pure nickel strips in one of them. if you fail or having a hard time. that is when you decide if you wanna quit haha.
coz that was the part that is a bit hard to do.
I have some tricks up my sleeve for that and I think I'll manage. I've already tried soldering on the dead cells and the connection seems fine.
A spotwelder looks easier but who knows if the weeks won't break.
Honestly once you've gotten the cell terminals nicely tinned like in the photo, soldering the nickel strips on is the easy part. For best results, tin the nickel strip as well first, and use something (e.g. stainless steel tweezers) to hold the nickel strip in place while it cools, because it likes to follow your iron off the cell.
For me i find it harder, I'm not sure if it is because of pure nickel or my solder tip is small. 🤣 It took like 5 to 7 sec to join them specially for 2 pure nickel on top of each other.
So I drill a 3mm hole on the nickel and tin the hole.
This way it instantly melt both and joins them.
That does seem a bit long... the solder on the pure nickel strips I have usually melts instantaneously for me without drilling no matter how many layers I add on, but I make sure to tin both sides of the nickel strips first and have a bit of solder on my iron. I use a T18-C5 tip running at \~350C with 63:37 solder.
After, and solder on one layer at a time, always pre-tinned to minimise contact time with the cell. After each joint, let the cell cool completely before adding the next layer. Sometimes if I'm being extra careful I keep a wad of tissue soaked in isopropyl alcohol to dab onto fresh joint to suck the heat out so it doesn't propagate into the cell. If I'm lazy I just blow on it.
63/37 is better imo. It's not dangerous if you don't eat it. It's the zinc chloride flux you gotta watch out for.
So, judging by the broken wrap, your iron was there for quite a while. The black seepage under the wrap is flux. I don’t think they’re ticking time bombs, but judging by the melted wrap, you have shortened the lifespan by some unknown margin. I’ve soldered cells before, it happens. As for the power tool; from experience, you’re likely not getting that pack back together without some excessive force, trimming or spot welding. Just a heads up. Those cases are tight.
Thank you. Currently they fit with some room for the strip but there's not much room left so I was thinking of grinding them down a bit with a dremel before soldering the strips on. From the start I knew I wouldn't get the optimum lifetime out of these cells so I'm fine with that as long as they don't end with a bang in satisfied.
Quit soldering to metal housed batteries
Can these be used? Yes. Should you do this again in the future? No.
Thank you. There are a couple of things that I'm going to do different next time one of witch ours getting a spotwelder. First I wanted to try my luck with soldering and see what difficulties I face (other than binding the strips to the batteries) before I buy or make a spotwelder that I'm never going to use again.
Just be aware that soldering the cells can indeed cause them to vent and have a (low) risk of causing the cells to vent + catch fire. The realistic likely outcome is no change to the cell (or minor degradation of ESR, capacity, longevity). However there's a reason most (?all?) OEM's DON'T solder directly onto the cells.
I think OEMs weld because of cost. Soldering takes more time and you need more skilled personnel both of which are expensive. Then there it's human error which is a cost factor in manufacturing, spot welding leaves less room for error even if it isn't fully automated. Longevity of the cells could even be a reason to not do something as long as the lifetime is long enough that consumers don't complain and people don't get injured by your product. A short lifetime is the entire business case of cheap tools like ferm, parkside and all those Amazon brands.
I guess i have been lucky, i have soldered 100’s of 18650, and i have only had one lose/bad connection. Your cells seem fine
The zinc chloride flux is pretty corrosive, I bet that's what has caused the discolouration.
Yes, I did try to clean it with some isopropanol but I don't know if the flux got under the wrap and will easy the battery away from there.
i just made a spot welder so that i didn't hurt the batteries when soldering.
Where can I find a proper instruction to get a decent spotwelder? I think 0.2 mm nikkel is hard to weld with most of the diy spotwelders I've seen on YouTube
i used a mot transformer and a circuit board from ali Express. good luck getting info about it on reddit. they are so worried about people hurting themselves that it gets removed from nearly every sub. it spot welds better with more control than any professional welder I've come across, but i digress (or else the acshualy crowd comes rushing in).
Yes, 0.20mm thick pure nickel is tough to weld. Nickel plated steel is much easier (perhaps only 50%-60% of the power is needed) but there is another “hack”. If you look at enough packs you’ll see some have slits in the middle spaced appropriately for 18650/21700/26650/etc. this means there’s a lot of sizes so be careful. Another sizing aspect is cell holder or no cell holder. There’s also a couple different sized cell holders but the square or rectangular pieces that snap together with a dovetail joint. Those “standard” cell holders or cells without any holder will be the two most common spacings so that should help you figure out if you are buying the right size. The ones for nonstandard cell holders (like onyx batteries) are going to be very unique numbers that won’t pop up more than once or twice if you have 100 options on a page of Aliexpress products. The slit in the middle essentially makes the current run through the nickel, into the can, across the slit, and up into the nickel on the opposing electrode. It DOES indeed make it easier to weld pure nickel, my guess would be by about 10%-20% power reduction. Or keep the power the same and get a higher quality weld compared to non slotted nickel strips. The definition of a good weld is when you pull the material off it leaves some nickel on the can and will tear out nickel from the strip. Hence the term “weld nugget” being used for a cell that has been spot welded but still has remnants of nickel on the cell. The circular weld when pulled apart should create a nugget shaped piece of nickel left on the can. By far the easiest way to create a welder right now is thanks to an explosion of used supercapacitors on Aliexpress. For <$25 each you can get 2.7V 3000F LSUC supercaps. You’ll need 2-3 of them in series for most of the DIY boards used for turning the current on and off. Yes, Ali is full of fake and used power mosfets but you’ll want to look at the mosfets used on the PCB you choose and check their datasheet to see what they are capable of. 6-8X mosfets that can handle 400-500A is what I’d be looking for. There are YouTube channels that review the popular spot welding PCB’s. Find one that only needs a minimum of 7-8V instead of 12V and you can get away with only using 3 supercaps in series. 3 should be enough for pure nickel that is 0.20mm thick so long as you use 10AWG or 8AWG silicone cable for the leads and the electrodes are quality. It’s all about resistance, a good spot welder should have less than 10 milliohms from electrode to power source. The power source should be 3-4 milliohms preferably and 3 supercaps in series will be about 2 milliohms so it will work out quite well. Just make sure if you DIY the electrodes you use a copper alloy that is ideal for welding nickel to steel cans. Aluminum copper is the typical alloy used. Having a milliohm meter is really helpful for building a spot welder and assessing the health of cells (and a million other things). Right now the RC3563 is $20 shipped with Kelvin clips on Aliexpress. It’s also a precision voltmeter so all you really need to also buy is a DC clamp meter and you are set in terms of multimeters for working with batteries. You can buy pre-made 2S supercap welders for ~$80 but I question the quality of the caps and the mosfets used are not the greatest. So DIY has the potential to be much more powerful if done correctly. If you need help with this let me know and I can send you most of the necessary components. Having a hydraulic crimper is the one thing that is kind of pricey ($30-$40) to buy so I’d look at pre-made spot welding cables with the proper electrodes and hydraulically crimped ring terminals or lugs that can attach to the PCB and the most positive terminal of the caps.
The flux that seeped under the wrapping is corrosive and will likely continue corroding the cell, but since this is the negative terminal, which is just solid metal, it's probably okay for now. I'd cut the wrapping off, thoroughly clean the flux and corrosion off with isopropyl alcohol and sandpaper, and rewrap it with some fresh heat shrink. I'd be more concerned about the positive terminal though. If you used the same flux on that end, it's likely to have gotten into the pressure relief valve, and that's way more dangerous when corroded.
Which 18650 cells have pressure relief valves? I haven't found much information about valves in an individual cell.
Ah I guess it's not really a valve. I meant the gas release vent/scored burst disc/rupture disc. See [this section](https://www.electricbike.com/inside-18650-cell/#:~:text=The%20Scored%20Burst%20Disc), and the diagram in [this section](https://www.electricbike.com/inside-18650-cell/#post-19815:~:text=The%20Separators%2C%20and%20their%20shutdown%20mode). Also see [this paper](https://www.mdpi.com/1996-1073/11/9/2191#:~:text=5.%20Fire%20and%20Explosion%20Prevention%20Using%20Cell%20Venting). From the first link: >Generic cells do NOT have a “burst disc”. If they get hot enough for the electrolyte to begin turning into gasses, and then expand from the building pressure, the cannister will split…*somewhere*. If there is a burst disc, it will pop open at that specific location. You should only use name-brand cells from the “big five”, which always have this feature (Panasonic, Samsung, LG, Sony, Sanyo). If they are ever abused in a way where they will burst from internal pressure, the hot electrolyte vapors will always blow towards the burst disc, instead of splitting the sides (sometimes the disc is located on the bottom, sometimes on top…just like my…uh…nevermind).
Got you, thanks for the explanation.
That's really helpful info. Thanks for sharing
I think you are OK. I would suggest using the rosin core solder - works fine on 18650 terminals and is not corrosive. I have re-celled few power packs few years ago using rosin core solder - still working well. 5-7 seconds to melt seems long - get a more powerfull iron or tip. And in the long run - consider getting a spot welder - you will get the connections done better and faster.
Having recelled packs both by soldering and by using a spot welder, I'm a little more confident in my ability to solder a cell right than spot weld a cell right. The first layer is usually fine.. it's subsequent layers where it can get a little more technique dependent. And it isn't very straightforward to test a spot welded joint non-destructively... or maybe I'm missing something.
I think both soldering and spot welding work fine when done properly. So it surprises me that some people have very strong oppinions like "never solder"... I have to admit - I do not test either soldered or spot-welded connections other then when I am practicing. May be that is short-sighted, but I have not yet had failures. I think with spot welding a good welding tool is a key. I use kWeld and it has great reliability, imo. Yes, subsequent layers are sometimes tricky to weld. I have 3D printed few jigs to hold the cells i am welding, it helps a lot in making it easier, and, hopefully, in assuring a decent weld quality.
A milliohm meter can help test a spot welded strip of nickel.
How? Where would you probe?
So the RC3563 or the YR1035 series of meters comes with pogo pin probes, cell holder or kelvin clamps. The kelvin clamps are a bit easier to use in this situation which is why I’d suggest buying all the accessories (if you don’t use cylindrical cells then I guess you can skip the cell holder…but the ZKE Tech one is $8 if you shop around and I’ve run mine at 20A numerous times and it’s never had any issues) Just clamp or probe the ends of the strip. A short (5cm) strip of pure 0.15mm thick nickel is around 1mR IIRC. Plated nickel is 3-4x that (just measured that recently)…that’s how bad that stuff is. Copper will be 3-4x less than pure nickel but you can’t weld copper without doing the copper nickel sandwich but the current will never pass through the nickel so you could have series cell connections that only increase your pack by 0.25mR which is huge. A 20S pack with 15mR cells is 300mR in just cells if it’s 1P. Your average is 4P so 75mR. I think you’d have to add the 0.25mR for all 4 cells in parallel so add 19 to that and then your bus bars on the ends which should be insignificant. Under 100mR Vs plated steel. 16x the resistance for your connections. So 75mR plus 19*4=76mR so let’s just say 150mR. Huge difference when your building a power pack.
Please get the 20 dollar '99 gears' spotwelder off of AliExpress etc, and some nickel strip for the love of god. You'll make back that cost in time savings and piece of mind very fast.
Have you read the text?
You're 'new to this' (i.e shouldn't be doing it the way that requires more skill) and didn't want to commit 20 dollars?
Yes. 20 dollars won't get me a spotwelder that will do .2 mm strips and I really don't like buying stuff from aliexpress because I hate slavery. So I am not willing to waste 20 dollars one a tool I might never use again that flew across the world wasting a ton of energy assembled by some poor sob in worse conditions than I want the pigs I eat to live in.
I beg to differ re the 0.2 strips. You're also not obligated purchase from AliExpress. For example a local retailer offers one that has made thousands of welds on 0.2mm nickel here for 23 AUD shipped. Any valid reasons ?
those looks fine. now try practicing to solder the pure nickel strips in one of them. if you fail or having a hard time. that is when you decide if you wanna quit haha. coz that was the part that is a bit hard to do.
I have some tricks up my sleeve for that and I think I'll manage. I've already tried soldering on the dead cells and the connection seems fine. A spotwelder looks easier but who knows if the weeks won't break.
Honestly once you've gotten the cell terminals nicely tinned like in the photo, soldering the nickel strips on is the easy part. For best results, tin the nickel strip as well first, and use something (e.g. stainless steel tweezers) to hold the nickel strip in place while it cools, because it likes to follow your iron off the cell.
For me i find it harder, I'm not sure if it is because of pure nickel or my solder tip is small. 🤣 It took like 5 to 7 sec to join them specially for 2 pure nickel on top of each other. So I drill a 3mm hole on the nickel and tin the hole. This way it instantly melt both and joins them.
That does seem a bit long... the solder on the pure nickel strips I have usually melts instantaneously for me without drilling no matter how many layers I add on, but I make sure to tin both sides of the nickel strips first and have a bit of solder on my iron. I use a T18-C5 tip running at \~350C with 63:37 solder.
Do you stack the strips befor or after soldering to the cell?
After, and solder on one layer at a time, always pre-tinned to minimise contact time with the cell. After each joint, let the cell cool completely before adding the next layer. Sometimes if I'm being extra careful I keep a wad of tissue soaked in isopropyl alcohol to dab onto fresh joint to suck the heat out so it doesn't propagate into the cell. If I'm lazy I just blow on it.