battery spotwelder

I have one of those handheld spot welders from HF, and I do run it from a Variac to tone it down. I use 0.002" stainless steel foil as the test case, and can easily find a variac setting that neatly welds the foil sheets together without burning a hole. Having done that, one can then try welding a battery tab on. Will likely take a higher setting than for the foil, but the variac setting isn't that critical.

The 12-volt battery has the short-circuit current it has, which cannot be changed unless one has a carbon-pile power resistor handy.

Joe Gwinn

I have one of those handheld spot welders from HF, and I do run it from a Variac to tone it down. I use 0.002" stainless steel foil as the test case, and can easily find a variac setting that neatly welds the foil sheets together without burning a hole. Having done that, one can then try welding a battery tab on. Will likely take a higher setting than for the foil, but the variac setting isn't that critical.

Joe Gwinn

---------------------- Thanks. Have you encountered any settings or combinations you consider dangerous?

Only running too hot. So start at zero on the variac, and work your way up.

You may need some kind of fixture to hold the battery and tab, unless you have three hands.

Joe Gwinn

Only running too hot. So start at zero on the variac, and work your way up.

You may need some kind of fixture to hold the battery and tab, unless you have three hands.

Joe Gwinn

------------------------ I have a benchtop electronic assembly press that could hold the fixture and handpiece.

The handpiece pins compress a ways before closing the switch, and I can wire it in series with the foot switch to trigger the timer only when both are closed.

If you are making a generic powerpack / battery its no big deal. Your BMS choice will determine how it works. If you are rebuilding power tool battery packs some of them now have anti repair serialize components. You may be able to replace cells, but nothing else. Linus Tech Tips can sometimes be a good resource for this sort of thing, but I think they mostly produce information on YouTube.

Have a bucket of sand handy to drop batteries into, and be prepared to rush batteries outside. A lot of first timers seem to have issue until they get the "knack."

Linus Tech Tips also has a forum with quite an eclectic collection of topics. I searched for "battery spot welder" and found a few hits, this one has a little data in one post

:

"Anyway i bought the kWeld and it works amazing, i hooked it up to a cheep car battery from AutoZone ($70) and i was off welding all my batteries without issue. I was welding at about 65J each hit and did 6 spots on each battery and the welds are super strong and hard to tear apart using .2 nickel strips."

Didn't browse the other threads, and there are probably better search terms. Enjoy.

I used to replace mass spectrometer filaments by spotwelding

0.030"x0.001" rhenium ribbon to 316SS posts, using a capacitive discharge spot welder. As I recall it needed about 100-150J but rhenium has a much higher melting point than nickel. Too little and no-stickum, too much (over 200J?) and there was just a hole :-(.

I used to replace mass spectrometer filaments by spotwelding

0.030"x0.001" rhenium ribbon to 316SS posts, using a capacitive discharge spot welder. As I recall it needed about 100-150J but rhenium has a much higher melting point than nickel. Too little and no-stickum, too much (over 200J?) and there was just a hole :-(. Regards, Carl

---------------------- Thanks.

You fixed chem lab equipment? I used it but never learned repair.

That's a lot of energy. I built a battery fault simulator to the specs of [big US car company] that generated Load Dump pulses of close to that [nondisclosure agreement]. After a few pulses it overheated and fried their protection device, which may have been the reason for side terminal batteries.

A Load Dump occurs when the battery connection is corroded and opens from vibration while the rotor current is at max. Then the alternator behaves like an ignition or Tesla coil, converting the stored energy into output voltage that rises until something absorbs the current.

"The surge energy rating needed for the suppressor can be found by taking the integral of the surge power over time, resulting in approximately 85J." Or 0.5LI^2, 0.5CV^2.

After moving into aerospace I made an electrical and optical fixture for MOPA laser diodes with 0.001" x 0.005: Au ribbon bonded to the pads and free on the other end. That stuff is NOT easy to work with. The signal input needed to be a GHz transmission line with a custom series matching resistor which I made into a connector by arranging a plastic tab to bear down on the Au plated end pad, and slipped the ribbons under it. The power section ribbons were spliced with silver epoxy. That was the most demanding delicate job I ever had.

Have a bucket of sand handy to drop batteries into, and be prepared to rush batteries outside. A lot of first timers seem to have issue until they get the "knack." Bob La Londe

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Thanks, good precaution, I can use the stove hot ash bucket. I was planning to work outdoors anyway, to avoid smoke in the house. Are dead alkaline batteries good to practice on?

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I haven't seen a dead alkaline battery in years. They leak long before going dead. All the big brands. Sometimes they leak before the store can even sell them🙁

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I haven't seen a dead alkaline battery in years. They leak long before going dead. All the big brands. Sometimes they leak before the store can even sell them🙁

Leon Fisk

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Hmmm, I haven't seen leakage from primary cells in years. The Rayovac Renewals I bought in the 90's and still use sometimes leak a bit but haven't corroded the contacts, I wash and keep using them.

I bought a used Moultrie trail cam with a badly rusted battery contact spring that I repaired by soldering a nickel foil strip to the undamaged base.

<snip>

I've started using Energizer Lithium AA and AAA's. Expensive as all get out but will be worth it if they don't leak. It's only been a year or so, not long enough to learn much yet.

I've not had any leakage problem with rechargeables either but they aren't really the best choice for a lot of devices...

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Posted some pictures I took here (expire in 31 days):

The thermometer was a real pain to clean up. Has an outside probe cord. Decided it would be easiest to do it in place.

Battery dates were all good yet. I'd take a peek at the batteries off/on but you'd have to do it almost daily I think. All items worked till the leakage caused a problem. The TV remote and Timer are used daily🤷

I have not a clue. I've never done it. I did once spent an afternoon trying to solder (not lithium) cells with about an 80% failure rate. Never tried spot welding cells myself.

Interwetingly I watched one of the first if not the first video of the Linus Tech guys trying to make a power pack with lithium cells. They sent may of the tiny soldiers to the lithium cemetery.

Maybe it was their first video on using reclaimed cells. I forget. After a while it all runs together.

I have a couple or few battery packs for my 18V DeWalt drills/etc that I think have bad cells . I also have a TIG welder with a "spot" setting - though I think that is more accurately a "tack" setting . I also have an HF stud welder (body work) , and I think one of those might work to re weld battery tie strips in my battery packs . But which one ? The TIG is adjustable for both time and amperage , the stud welder is what it is . <stir-stir-stir>

<snip>

Posted some pictures I took here (expire in 31 days):

The thermometer was a real pain to clean up. Has an outside probe cord. Decided it would be easiest to do it in place.

Battery dates were all good yet. I'd take a peek at the batteries off/on but you'd have to do it almost daily I think. All items worked till the leakage caused a problem. The TV remote and Timer are used daily🤷

Leon Fisk Grand Rapids MI

------------------------------------ Your climate is similar to ours in New England. I wonder if your local stores received a batch that had been stored in a very hot warehouse somewhere else. When I was testing field returns I noticed short lifetimes of Lithiums from Arizona ambulances. The batteries internally logged their charge level and temperature histories.

<snip>

Maybe... but this has been going on for years now and bought from different stores. Some of the batteries came with product. I suspect it started when manufacturing was moved to China...

A very different "horse" but I've had really good luck with Eneloop rechargeables. They have "Made in Japan" on them🤷

Interwetingly I watched one of the first if not the first video of the Linus Tech guys trying to make a power pack with lithium cells. They sent may of the tiny soldiers to the lithium cemetery. Bob La Londe

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I bought most of a case of cell phone chargers that were nearing or at low voltage expiration, where the BMS shuts them off. By connecting a lab supply directly to the tab strips I brought almost all of them back to full charge, and top them off twice a year. They are all 18650s I can use to rebuild laptop batteries, if I can open them without irreparable damage. The immediate project is tabs on coin cells for the CMOS in laptops, though I bought the spotwelder for joining sheet metal and wire.

I have a couple or few battery packs for my 18V DeWalt drills/etc that I think have bad cells . I also have a TIG welder with a "spot" setting - though I think that is more accurately a "tack" setting . I also have an HF stud welder (body work) , and I think one of those might work to re weld battery tie strips in my battery packs . But which one ? The TIG is adjustable for both time and amperage , the stud welder is what it is . <stir-stir-stir>

Snag

---------------------- The few numerical specs I found for nickel tab spot welders ran around 1000A at 8-12V. Do you have a Variac to reduce the power of the stud welder? Their current rating, mainly for the carbon brush, is for continuous use because they are resistive and heat up and the catalogs say they can withstand 5 times or more current briefly and intermittently.

I've read that the resistance is necessary to reduce current between adjacent windings when the brush bridges them, the same as for DC motors. I think a few tenths of a volt drop at full load is enough. The brush composition has a voltage and resistance rating accordingly.