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quick dirty capacitor spot welder?

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coppercone2:
Ok, do you know if the caps can get hurt?

I don't mind it being a unit for thicker welds (psuedo bus bar) but I just am scared that the capacitors will experience destructive forces and should be current limited.

MosherIV:

--- Quote ---  Ok, do you know if the caps can get hurt?
--- End quote ---
Probably yes. Super caps are not designed for rapid discharge, they mainly for supplying voltage over a short period, ie battery backup.
You are better building a bank of capacitors. Cheap high values ones will work. Do not worry about esr, just get as much F as you can get.
Anything above 12V will work, the higher the voltage, the higher the current pulse!

MarkF:
Here is a DIY one:   https://www.instructables.com/id/Capacitive-Discharge-CD-Welder-for-battery-tabs/

james_s:
I built one I've been using for years. I used a bank of 22,000uF capacitors adding up to about 1F and a variable 24V power supply built around a LM317. For triggering I used the biggest stud mount SCR I could find for a few dollars on ebay. Total cost to build the thing was under $100 and it works great.

cur8xgo:

--- Quote from: coppercone2 on June 09, 2019, 05:27:21 pm ---Is there a peak current limit that the super capacitor needs to be designed with, or is it OK to short them out and rely on ESR?

--- End quote ---

Have you looked at the datasheet? Is this the one you are using?

https://www.mouser.com/datasheet/2/257/Maxwell_K2Series_DS_1015370-4-1179730.pdf

Maximum current = 680A

Short circuit current = 7700A (Current possible with short circuit from rated voltage. Do not use as an operating current. Just listed for information.)

I don't know if maximum current = peak pulse current. They talk about a non - repetitive peak current in their product guide but the word "peak" doesn't appear in the datasheet.



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