Spot welding on batteries with residual solder

S

steftn

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Jan 3, 2021
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Hey Folks,
has anyone tried to spot weld on batteries which have residual solder on it?
If yes, how does it work?

I have a bunch of good 18650 where the pre-owner did some soldering on the connectors. Removing the solder completely is actually rather difficult, you simply get never a 100% clean surface again, there is always some residual solder left.
I actually used compressed air to remove most of the solder after heating it up with an iron, works quite well (at least it is much quicker and less heat-intensive for the cell compared to using a vacuum system or solder wick). Just make sure you wear safety glasses and gloves as the hot solder will fly everywhere when you blow it away with compressed air.
But as I said, there is always a thin layer of solder left.
I am considering buying a spot welder, but I wont do it if you tell me now that it wont work to spot weld on solder-contaminated batteries.

Thank you!
 
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dont use compressed air to get rid of it on the positive side. if you done that bin all those cells. you will most likely gotten solder into the cavity where the cid sits.

You cant spot weld if there is solder left on the cell but its hard to say how much you have left? And if the cells already have been soldered and you also heat them again to remove the solder why not just solder them to your new system then spending time trying to remove it?
 
Hello daromer,

I actually checked the cid, they look all clean.
I also think spot welding might work, I just wanted to hear some experience from you guys.

Thank you.
 
Use a set of flush cutters to snip off as much as possible. This will also leave a flat-ish surface.

Or you could use a big a iron (100+W with a fat tip) with some solder wick and tap the cell for <1 second. Should be enough to melt the solder and pull it out with the wick. Since it's the Pos end, it's not quite as crucial on the duration, but you still want to minimize the heat soak.
I would use the flush cutters, imho.

Also, as daromer says, no compressed air. You don't want to lodge a piece of metal under cap and shell. This can lead to a fire. And not always quickly. You don't want a slow cooker and toss it into a bin and not know it until you have fireworks going off.

The spot welder will fuse through solder. Though, not sure how tight the weld will be, tho, as it won't be nickel to nickel weld.
 
Korishan said:
You don't want to lodge a piece of metal under cap and shell. This can lead to a fire.
Click to expand...
I actually re-wrap all the cells and this helps to find unwanted solder pieces. During this process I also take a look on the cid to make sure no debris is caught in there.
In hindsight, it was probably not a good idea to use compressed air, the solder is literally everywhere in the workshop...
 
Its a very bad idea and unless you have tiny camera you wont see if all crap is gone from inside the cide. If this is a small amount of cells bin them directly. I dont see the reason to use them.
 
daromer said:
If this is a small amount of cells bin them directly. I dont see the reason to use them.
Click to expand...

Or just solder those cells in a different smaller pack design. Different projects.
 
Korishan: if there is solder in the cid area they should not be used anymore. that could potentially make them dangerous to use if there is anything inside there. Note "potenatially". So do you want to add that on top of all other factors.
 
daromer said:
Korishan: if there is solder in the cid area they should not be used anymore. that could potentially make them dangerous to use if there is anything inside there. Note "potenatially". So do you want to add that on top of all other factors.
Click to expand...
I wasn't stating to use the cells that could possibly have solder in the CID area. I was stating that the cells that have solder on the ends instead of trying to remove the solder, use them for other projects instead of trying to build a large pack with them where spot welding is to be used.
Any that may have had solder drop/blown in the CID area should be tossed, imho. Those that have not been subjected to this could use for something else.
 
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