I need a capacitive discharge welder for batteries and have seen a number of builds that look promising and most run in the 12-32v range in the videos. I need to be able to do 2 welds quickly right after another, maybe 1 second in between so I'm planning on running 2 separate switched banks paralleled, one for each weld.

I've built a cap bank of 35v which should be alright as I'm planing on running around 25-28v or so but I'd also like to be able to do thicker pieces and am thinking that it would be easiest to jump the V up to 40-45 which would mean I need to use either higher V caps (say 50 or 63). I can also run the 2 banks in series so it would give me 70V but it would drop the uf a lot.

If I dual banks of 30 35v 4,700 uf caps and 30 2200uvfor 207,000 uf @35v were to be run in series I'd effectively have a 70v cap bank but IDK how to determine the capacitance.

207,000 uf @ 35v = ~127 joules

What would I expect by running them in series at 70V (potential juoles, they won't be run at 70v, but less) and can I run a bank of multiple paralleled caps like this in series? 0

 

I need a capacitive discharge welder for batteries and have seen a number of builds that look promising and most run in the 12-32v range in the videos. I need to be able to do 2 welds quickly right after another, maybe 1 second in between so I'm planning on running 2 separate switched banks paralleled, one for each weld.

I've built a cap bank of 35v which should be alright as I'm planing on running around 25-28v or so but I'd also like to be able to do thicker pieces and am thinking that it would be easiest to jump the V up to 40-45 which would mean I need to use either higher V caps (say 50 or 63). I can also run the 2 banks in series so it would give me 70V but it would drop the uf a lot.

If I dual banks of 30 35v 4,700 uf caps and 30 2200uvfor 207,000 uf @35v were to be run in series I'd effectively have a 70v cap bank but IDK how to determine the capacitance.

207,000 uf @ 35v = ~127 joules

What would I expect by running them in series at 70V (potential juoles, they won't be run at 70v, but less) and can I run a bank of multiple paralleled caps like this in series? 0

Unfortunately capacitance goes down when placed in series, and it may be limited the most by the smallest capacitor. Parallel capacitance is C1+C2... +Cn. Essentially the opposite of resistance formulas.

You do not need such big voltages. Large voltages means larger ESR, and most of the voltage will be dropped on the ESR. Do the math, with your ESR and weld resistance. It will not be good for your weld or the caps. ~5-12V would be better. So maybe try a few of these in series.
https://www.mouser.com/ProductDetai...9HefNWqpng9ga65R3xtBpWExhK9uEe0xeq%2bEtNNRQ==

Then for charging, try a inductor with flyback diode and PWM. This will allow you to limit the current a bit. You will then need a PS like this.
https://www.ebay.com/itm/AC-110V-22...Light-/152134115704?oid=202281702579#shpCntId
(12V 60A or 5V 72A)

 

This is a spot welder for nickel strip??? you are spot welding 18650s or similar ???

No need for any capacitors ...

A normal 12 V lead acid car battery will deliver the current you need .. or similar ... I use 3s 50p 18650's ...11.2V ..... switch current with mosfets ,or motor bike starter relay.