Capacitor bank for spot welder

Hey guys,

I had someone a while back telling me he built a capacitor bank to help run a spot welder on home grid at high settings without tripping the switch and he also said that it provides "cleaner" current thus making better spot welds (although I doubt that one).
He also said that it may take a second for the caps to charge between welds which can be a bit annoying in case I want to work fast so the first question is, can I use super capacitors?

Main question is, can you guys help me figuring out which and how many caps would I need? (220v grid)
Which other components would be required?
Is it possible doing without a PCB and not being a fire hazard?

I am no expert when it comes to electronics. That being said, it appears that the less voltage you use, the better. The kCap power supply for the kWeld timer (used for spot welding bus-ribbon to connect 18650 cells) typically is charged by a 6V charger, and them when the timer trips it, the very high amps are dumped in a very stable and predictable manner.

The most common power supply is a high -amp 12V car starter battery. A secondary power supply that has occasionally be used is a small LiPo 65C 3S pack, with a nominal 11.1V charge.

LiPo packs are problematic to ship, but many builders already have a LiPo pack, and are familiar with all of the appropriate precautions that are well advised. Capacitor banks can be shipped with no special regulations. 6V and 12V chargers are cheap and readily available, so a capacitor bank is a desirable option. I encourage everyone with an interest in this to continue developing capacitor banks for spot-welding, so there are more options...

When comparing two super-capacitor options for this job, the one with the lower Equivalent Series Resistance (ESR) is usually the better-performing choice.

++ +

Im not looking for a spot welder, I'm looking for a capacitor bank to go from my wall outlet to my professional spot welder in order to run it at high settings without tripping the grid.

rg12 said:

Im not looking for a spot welder, I'm looking for a capacitor bank to go from my wall outlet to my professional spot welder in order to run it at high settings without tripping the grid.

Click to expand...

Unless your welder runs on DC power, caps aren't going to do anything for you.

Supercaps have a rated voltage of 2.7V, so even if you rectify your 220V, that's a whole lot of caps (and a whole lot of juice stored up, ready to spoil your day).

Which 220V spot welder model are you using, and...do you have a link to the cap bank you referenced?

I have a simple one and ordering a bigger one with air pressure electrodes, still don't have an exact model.
I don't have a link to a cap bank, I didn't know that these things come ready to go, or at least for my use (I wanted to build one but of course I rather buy a ready to use one although I doubt it exists).

EDIT:
I guess it would be that one:
https://www.aliexpress.com/item/1pc...ot-welder-small-handheld-diy/32858874492.html

rg12 said:

Hey guys,

I had someone a while back telling me he built a capacitor bank to help run a spot welder on home grid at high settings without tripping the switch and he also said that it provides "cleaner" current thus making better spot welds (although I doubt that one).
He also said that it may take a second for the caps to charge between welds which can be a bit annoying in case I want to work fast so the first question is, can I use super capacitors?

Main question is, can you guys help me figuring out which and how many caps would I need? (220v grid)
Which other components would be required?
Is it possible doing without a PCB and not being a fire hazard?

Click to expand...

Your "someone" is full of bs because that makes no sense at all for a transformer based spot welder.

He can have the house full of capacitors and it would make zero difference.

Really? well, I care less about smoothing the current and more about making the grid not trip, so if the capacitor bank can be used as some kind of a charged device that prevents that then thats all I need.
Same like in car audio, sometimes you got too many amps drawing high current from your battery making your headlights dim on high current demand with the subwoofer banging so they put a very big capacitor between the battery and the amps and it does the job very well.

Capacitors can be used to store up DC current, and the 220V power coming from your mains supply is AC, so...the claim your friend made is confusing. But again, I am no expert in all the ways that electronics can be assembled into a clever device. Without knowing exactly how your friend is doing this, there is no way to help you search for the proper part...

but there are AC capacitors...

rg12 said:

but there are AC capacitors...

Click to expand...

They dont work that way. They only help with lowering the crap the transformer puts back on the grid. Remember the (AM) radio would go static when you turn a piece of electronics on? That is basicaly what a AC cap tries to lower. Together with coils and stuff.

I have a small inverter style of welder. When the 120V AC goes into the welder, a full bridge rectifier converts it to 120V DC, which is then converted into a very high frequency AC, which is then rectified back into DC.

It sounds nuts (and to be honest, I may not actually understand the process right). The point is, that...I now have a light-duty welder that is very small, because it does not use a vary large and heavy transformer. Doing that leverages dirt-cheap Chinese electronics to make a highly portable unit that can be powered by a portable generator, when a repair needs to be made in a remote area.

I said all of that so I can now say this. I don't know how your friends booster system works, and without you telling us how, nobody here has done that before, so...we need more information from your friend. PS, why is he refusing to tell you how he did it, and what parts he used?

He doesn't refuse to tell me, he even offered to come and teach me how to do that but that was a while back and he was some random potential customer that called me and we got into a long talk.
At the time I was satisfied with my welder but am now ordering a much stronger one and would need something like he talked about for sure.