Super Capacitors for Welder from Cheap Chinese Vendors

[rewsiffer]

Hi, I am interested in building spot welder, but am hesitant to drop the $ to buy nice super capacitors. However, I recently found numerous super capacitors from the usual chinese sources(links below).

100F 2.7V
1F 5.5V
10F 2.7V

Does anyone have experience with these? Are they complete crap? Will they suffice for low voltage spot welding? Will they blow up in my face?

I would assume like many other items on these sites, the specs are vastly overrated. However, considering their price, I could wire up an enormous bank of them.

Please advise.

 

[litespeed]

When I built my CD welder I bought 3-1 farrad caps at a cost of about $75 a piece for computer grade 25 volt capacitor. From memory Mine are about 2.5 inches x 7 inches long........

I'm going to tell you those are NOT 1 farrad caps.

Tom

 

[liveforphysics]

Super caps ESR and ESL and pulse power generally is pathetic.

 

[Chalo]

When I built my CD welder I bought 3-1 farrad caps at a cost of about $75 a piece for computer grade 25 volt capacitor. From memory Mine are about 2.5 inches x 7 inches long........

I'm going to tell you those are NOT 1 farrad caps.

Tom

Um, yes they are. You're probably comparing aluminum electrolytic caps to these things.

I use very similar 1.5F, 5.5V caps for standlights in bicycle generator LED lights. They provide useful light for a minute or more and a visible glow for hours, even though the LED can use only a small fraction of the available capacitance due to its limited operating voltage range.

 

[rewsiffer]

Thanks for all the info.

Even if they have terrible ESR and ESL, couldn't I still wire up a large bank of them, maybe 2 in series to 5.5v, and offset their individual shortcomings with greater numbers? It would still be much cheaper than quality capacitors.

 

[liveforphysics]

Thanks for all the info.

Even if they have terrible ESR and ESL, couldn't I still wire up a large bank of them, maybe 2 in series to 5.5v, and offset their individual shortcomings with greater numbers? It would still be much cheaper than quality capacitors.

Nope, because they hold enough energy to eventually slowly melt through things, they just have pathetic power delivery. Pretty much exactly backwards of what you want for a spot welder (if you want a spot welder which means you're already lost).