Wanted: Battery spot welder

[Swwils]

Pretty good.



￡17.87 44%OFF | DIY Handheld 6 Gears Spot Welding Portable Adjustable Mini 0. 12mm For 18650 Battery Spot Welder Machine Tool Kit DIY Handheld
https://a.aliexpress.com/_EvdyKmx

[Mr Gus]

Yes, thats the basic 6 setting unit, which is typical of this generic on ali express.
Some sellers list its limitations, others do not.

The other type has a useful display, ammeter (less guesswork where the voltage drop & bad welds are going to be) & 30 step settings.

https://m.aliexpress.com/item/100500485 ... 7245%21rec

Annoying thing is, these are designed for 18650's & the likes but the units themselves have slim packet li-ion envelopes (which I hate & don't particularly trust) rather than the atypical 18650 combo via a spring load battery compartment ..jings, logic & multi modality out the window!

[Oldgreybeard]

I wouldn't get too concerned about settings, to be honest. Many years ago (2007) I made a lithium battery tab welder from a bank of second-hand high value capacitors and a large, very high surge current thyristor. There were no controls. I linked all the capacitors together with 1" x 1/8" copper bars and ran fat cables to the copper electrodes, with a trigger button to turn the thyristor on. The only control was the charge voltage of the capacitor bank, which set the total energy available for each weld. I used fifteen, 97,000uF, 20V, very low ESR surplus capacitors that I bought for around £10, wired them to a 180RKI40PbF thyristor (surge current 4,000A) and it worked like a charm. Here's a photo of the raw unit, before I boxed it up:

Capacitor bank.jpg (38.61 KiB) Viewed 4331 times

This is the finished tab welder, with the copper electrodes and trigger switch on the end of the operating lever. To use it the battery, with nickel tab, was placed under the electrodes, the lever was pulled down and the button pressed to trigger the thyristor. Those 35mm² cables connecting the capacitor bank to the electrodes would jump a few inches with each discharge, as they were usually carrying a thousand amps or so for a millisecond or two. The energy for each weld was set by adjusting the home made power supply on the left. More voltage equalled more energy, with the weld energy being proportional to the square of the charge voltage:

Welder.jpg (19.05 KiB) Viewed 4331 times

[Mr Gus]

I get it, but the O/S for what's left if my brain needs context & visible measurement to get over the hump, not an ocd thing but reconnected synaptic insistence that helps me do & retain via precise repetition, rather than letting battery voltage go to low etc.

[Joeboy]

Off over to Marmaris tomorrow Gus, I'll see what he's got. Will look for a couple of usb led lights while I'm in to fortify the Tutkish bunker!

[Joeboy]

Laggy DP, apologies..

[Mr Gus]

Fingers crossed, cheers Joe.

[Joeboy]

Sorry Gus, he knew what it was but doesn't carry it.

[Mr Gus]

Aw well, thanks for trying Joe, with the price difference on the likes of the powerbank you bought, diy is a "why bother" scenario for locals, may be worth you investigating the "on the wall" size offerings to expand your knowledge.

Tha brick looks like it has some serious potential if the specs match (physical seller 'll be on top of that)

[Joeboy]

Aw well, thanks for trying Joe, with the price difference on the likes of the powerbank you bought, diy is a "why bother" scenario for locals, may be worth you investigating the "on the wall" size offerings to expand your knowledge.

Tha brick looks like it has some serious potential if the specs match (physical seller 'll be on top of that)

You,'re right on the potential. Although tbh, sometimes i have to take the hand off the throttle. I can't think of a way to easily quantify the powerbanks storage volume? Although I'd happily accept suggestions?