Thanks, I’ll have look and ask around in my circle if more are interested and just order in the EU…
Unno. When I used to spot-weld sub-C NiCd cells, I’d take a thin strip of metal, put a dimple in it where I’d want the weld to be, securely have one contact go right to the cell, and the other end to the tin strip. Carefully lower it down into place, and ❋pouf!❋, the arc would weld that critter tight.
Used a few of beefy caps, like 80,000µF power-supply caps with screw terminals, in parallel, with ~14ga wire coming together at the “probes”.
Was enough to “stick” a screwdriver to whatever it’d touch, so…
Maybe not for critical applications, but for connection a few batteries a DIY effort is fine (It is easy to test if the welding works and is solid enough).
The cheap Chine spot welder and the DIY design, will probably work about the same and the DIY design may last longer.
Exactly, we aren’t building automobiles or aircraft here. It’s not rocket science to spot weld a tab on a battery.
I don’t think any of us are proposing to use this for high precision manufacturing of battery packs. Welding on button tops, or building a multi cell battery pack is closer to the truth. Perhaps even rebuilding a cordless tool battery.
The instructable linked has a video that shows the build process. I shall attempt to link it here que’ed up to the place where he starts testing it.
Be forewarned, you may want to have your safety glasses on before clicking the link.
^ Peter, watch that video and realize the cells remain wrapped. There’s also multiple welds on each cell on each tab. So the likelihood that a single tab would have 4+ welds fail for the tab to come completely loose and short something is not going to happen I dare say.
Engage safety squints as some might say…
Well, it takes no precision or much thought process.
Target cell
Button
Place button on top of cell and hit the flats with the spot welder
Place cardboard gasket on top and clear shrink wrap
Shrink the wrap with a heat gun, and your done
Not me.
Fwiw, when I’d spot-weld sub-Cs, I’d do it with the cells essentially side-by-side, then fold then over to be coaxial (ie, a battery “stick”). So having a mil-spec weld wasn’t necessary, as they’d be just lying in a trench or rack and not get jiggled around too much. Soldering was pure Hell, but a quick spot-weld made things lots easier.
Ha, cute!
I built a mot welder last year. I control it wth a footswitch to a relay. Most of the time it works well but I have a twitchy foot :person_facepalming:
I’ve been trying to think of a way to do a timed double pulse. Wonder if I could use the timing part of the circuit. Hmm?
The version of the board I ordered has an auto pulse feature which would require no use of a foot switch. It sees both probes are in place on the strip, waits 2 seconds, and then pulses the welder.
Do you think the auto pulse could control my relay instead of the mosfets? Not sure if the relay would be responsive enough. I’m assuming not…
i have a question.everybody advice me. please.
if i don’t spot welder. but i Place button on top of cell only.Will it works?
and 2nd choice
if i use little magnet place between button and flat cell .Will it works?
- It will possibly work for low drain applications where there is a strong spring to hold it in place, and the button top never gets any side load (twisting).
- AFAIK, a magnet won’t do any good, as the button top is non-magnetic material. (I’m likely wrong about this, though.)
No, you’re right about that. At least the buttons I have are non-magnetic.
For anyone wondering, professional battery spot welders (resistance welders) use the two probes side by side, not top and bottom like a traditional spot welder. So no need to access the underside of the flat top.
I have used some very high end Miyachi welders at work, the two copper electrode tips just sit side by side, how far apart depends on the type of cells, tab material, etc being welded.
Would love a simple setup like this DIY welder for home use on personal projects, and I see no reason a good weld couldn’t be made with something like this.
I’m new here but Peter I get a chuckle out of you telling a guy who does seemingly has done this for a living that he’s wrong.
You are correct, there are many different electrode configurations. My comment was geared towards the stuff we typically deal with here, which are cylindrical cells in a metal can with a metal top, either flat or button. I believe that is the primary purpose of this particular DIY welder. If we get into prismatic cells the process will be different.
I don’t weld batteries for a living, but I am an engineer and have to do it from time to time. There are many variables that go into making a consistent and reliable weld. The professional machines are generally current controlled and pulse very well controlled currents.
The thing is, I am going to accept different things for different use cases. In a mission critical application, get it done by a pro to be sure it will be perfect. For most of us here it isn’t life or death, so we can deal with “good enough”.
There is always a risk of catastrophic failure of a cell when welding, especially with a DIY device. This can be mitigated though by just starting at low power and ramping up.
Because this is not precision pulses, welding the electrode to the workpiece is likely, but not a big deal. Just don’t pulse so hard that the tab gets holes in it. When using never put an electrode directly on the cell. Both electrodes should be on the tab itself. Ideally you want constant pressure, so spring loaded electrodes are best if possible.
Welding a button top directly to the cell is possible, generally though I usually like to weld the button to a tab, then the tab to the battery, and fold the tab over under the button. Then insulating disk and heatshrink.
EDIT: Forgot to mention, the multipath problem for current with series probe configuration can be mitigated by putting slots in the tab material. This is really only necessary with thicker materials though. Might be useful for those FT button tops to put a little slot between the two electrode contact points if going direct to the cell. Many high current devices where super thick tabs are needed use this slot technique, that is why you will see some power tool packs with slots in the tab where the battery is attached.