Capacitor spot welding: high voltage

[james98118]

Hi all,
I have been kicking around how I want to spot weld a battery pack together. I will need a 0.2 or 0.3mm weld capable welder. I am leaning toward a capacitor spot welder. I came across some high voltage capacitors: 550mFd @450VDC and 6,000UD @ 400VDC.

I thought that either could be great to weld due to the high voltage pushing large amounts of energy through the weld. When I ran the calcs These things would be pushing thousands of amps! I think they would fuse the relay which is only rated to 300amps.

Does anyone have any knowledge/experience working with high voltage capacitors?

 

[flippy]

high voltage is something you dont want. its way too probematic to work with, especially in DC wich makes it several times harder.

the best example you should work to (or just buy) is the kweld and the kcap addon. it only runs at 8.4V but can still dish out 1500A or more.

i dont see how you would be able to control such a voltage properly without utterly blowing your cells to pieces while your face is just inches away from it.

 

[spinningmagnets]

Somewhere between 60V and 100V, electricity can penetrate dry human skin. High amps can cause a painful burn.

That being said, it's the amps that cause the heat that welds the two metals together. Plenty of experience on this forum using 8V-12V, and that works fine.

Most home wall sockets are protected by a 15A fuse, so 110V X 15A = 1650W. This means if you plug in a device that converts the watts into high amps, 1600W is near the max you'll be able to get. The kWeld has enjoyed some success, and it typically uses a car battery providing 12V, and usually 800A (9600W).

One of the benefits of using higher voltage is that you can get high watts at low amps, and the devices run cooler.

 

[batteryGOLD]

playing with caps? capacitor is great at short circuits.
but can't control pulse duration..
think that way you could even go for a micro-oven transformer inverted, for K amps delivery


better go for a safe tested design starting at$50 spot welder at wish or other selling platforms

I use kweld spot welder Europe production DE tech

Question of tha day: How many amps you need to melt a car chassis? supposing positive electrode at front car chassiss, and negative at back metal car chassis

 

[flippy]

Question of tha day: How many amps you need to melt a car chassis? supposing positive electrode at front car chassiss, and negative at back metal car chassis

https://www.youtube.com/watch?v=_j2jESz7Zl8

 

[batteryGOLD]

that is some crazy stuff
why some explosions? , maybe mixing different materials..
What happen if put two, positive and negative electrodes inside melted metal at high current? maybe some bubble explosions..

that is not melting a car chassis.. 10K amps could get chassi hot, but for melting need a lot more amps

 

[flippy]

that is some crazy stuff
why some explosions? , maybe mixing different materials..
What happen if put two, positive and negative electrodes inside melted metal at high current? maybe some bubble explosions..

that is not melting a car chassis.. 10K amps could get chassi hot, but for melting need a lot more amps

explosions happens because its a stupid high voltage combined with an equally stupid amount of amps. the thing that conducts simply vaporises. wich is why they just drop the rods in and pull out only when a proper arc is made.

when its liquid: https://www.youtube.com/watch?v=3gg9_zTlg4M

 

[batteryGOLD]

short circuit plasma melts everything, the more amps better, but high voltage is great because keep on sending arc´s. kind of short circuit at distance.. 1MV will do a fantastic short circuit/explosion, and 0,1V will pull 100KA current melts any metal.

universe started from bigbang, two opposite charged particles collided, the potential differential between particles was so high that was a huge short circuit released all tha universe. just telling..

anyway, check this pro spots

https://ibb.co/CsMm1X7

kWeld does this nice 4 double spots
a simple capacitor will not have control on discharge. To get great spots is needed to control on/off time current variables

 

[flippy]

arcs is something you dont want.

 

[dequinox]

I'm in the car-battery with charger and time-delay circuit with big relay camp more than other types of welders. The pocket welders from alibaba etc are neat, and I would presume good for repairs and maybe one-off packs. If you're going to build a lot, a low-voltage source with a relay is probably your best bet for the $.

The microwave transformer builds you see online do a similar thing, high amps at low voltage, via stepping down the 120V at the wall to something quite a bit lower for the spot welds.

 

[litespeed]

My home built 800 watt second CD welder ( https://endless-sphere.com/forums/viewtopic.php?t=68521 ) goes up to 23.2 volts which would make it considered “high voltage” in a world of 5 to 12 volt short circuit style welders. Mine is more of a precision type weld where the others are a “release the Cracon” type weld. CD welders are used for fine work like jewelry making/repairs and intricate electronics/metal work. Now days the cheaper welders make sense. To try and buy what I have or the equivalent would cost you $4000-8000 and to build would easily cost you $1500 assuming you could find the three 1 farad caps to do what the others will do for $100-250. Only advantage to a CD welder is a more compact/lighter package even at 41 lbs since you don’t have to lug a car/rv/boat battery around with you.

Tom

 

[james98118]

Thanks all :thumb: