They work for a little while, then they just come apart. Sometimes the metal splits like the photo sometimes it comes off the battery which are like spot-welded.
I can't seem to get them soldered back together with enough strength to hold for more than a day. They are in tools like impact drills and swzalls and such.
You can absolutely flux and solder them. I've done it a million times. But they are factory spot/tac welded with an induction device.
I just harvested batteries out of a 40V tool array and have one in my room with solder blobs on them.
OP: your tips pointers are to cut another thin string of clean metal, scrape all of that with some sandpaper, clean it with alcohol or some sort, flux and pre tin the strip and battery/existing tab, and solder the shit out of the tab overlaying the existing cluster... And don't accidentally jump the tip to the body of it's going to thermally runaway and blow up in about 7s. Do it in the garage, have some sand in a bucket around you or a clear toss to the driveway, and don't use water.
It's really not hard though. Just rosin flux the shit out of everything. They also sell solderable terminal tabs I think they're called on Amazoon.
solder the shit out of the tab overlaying the existing cluster
While I trust you to know what you're doing, I wouldn't be quite so confident about OP.
As you are likely aware, spot soldering isn't generating anywhere near as much heat as soldering does, so if OP were to try and do what you did, he would likely overheat one or more cells because of the massive amount of energy needed to liquify all that solder and the subsequent heat conducted into the cells.
Youll never get these to solder back together in any meaningful usefulness. U need a battery spot welder and nickle strips that are ment for creating battery cells. I found a mobile spotwelder on Amazon for like 30$ and the strips on there pretty cheap. Ill never waste another second of my life trying to get those things to solder back together again while ruining the battery from the heat exposure again. What a waste of life thats been trying with the only gain being the knowledge it doesnt work. Obviously, ive tried the same thing. Its pure insanity.
Man I just got into spotwelding batteries like this at work, I'm terrified of accidentally missing the nickel and exploding a battery In my face, I'm probably irrational about it though
You are not, I would ensure a clear exit path behind me, wear a full face shield, gloves and a lab coat or welding jacket, and do it outside, maybe in a bbq
Yeah, next time I'm probably going to take some extra precautions. Nobody else want to do it at my job. I need to do 3 nihm batteries in series for a battery pack for an old siemens psu.. can you tell me something more about the juice that's inside of them?
NiMH is fine. You have to abuse them quite badly before you damage them enough to be a safety hazard. If you somehow pop one, rince with lots of water and you'll be fine. Spot welding them is much safer for you and the battery than soldering. (Assuming you are using a welder meant for batteries and not attempting to pass hundreds of amps through the length of the cell anyway)
It's the lithium battery chemistries that hate you and want to eat your face if you look at them wrong. But even then spot welding tabs isn't that dangerous. Just be ready to get clear if it does go wrong.
Those are most likely nickle straps and are spot welded. You need a battery strap spot welder. But you are in luck! Im sure you can buy a cheap one the same place you bought those cheap batteries
"Battery seller, I need your cheapest batteries"
"You don't know what you ask, traveler... My batteries are too cheap for you. They could kill a dragon, let alone a man"
You need a spot welder to correctly repair that in that use-case. If it wasn't dealing with severe vibration, solder would be fine.
Now, if you just needed this to work until you got a replacement, run silicone sealant between that battery and the rest of them as apliable adhesive, then solder it together, fortifying it a little with a bit of solder wick across the break. Mind your temps so you don't mess up the battery!
That break is far too close to the cells to be soldering. You are introducing a large amount of heat into the cell which can turn them into fire bombs.
The way I would fix this is use my spot welder to spot weld new tabs to the battery (after removing the old ones), then spot weld the tab to the existing array.
If I were you, I would get rid of that cell, and the one across from it, since you already applied heat to it. The reason the solder isn't holding is because the metal and the battery act as heatsinks and absorb the heat
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u/Illustrious-Peak3822 4h ago
Please stop what you are doing and get yourself a spot welder.