Can I damage my supercap by short it in a very short period of time?

I want to create a CD spot welder using couple of supercaps, a car starter relay and a microcontroller. I'm wondering if there's any danger to just use the starter relay for timing control and don't limit the discharge current?

I have limited experience with supercaps, but I have not seen a max discharge current in the specs. Back in the HV days, we routinely shorted out power capacitors with a screwdriver before working on a circuit.

So, you want to spot-weld your CD's? Sounds drastic.

What does the data sheet say?

I will go out on a limb and suggest the very high ESR is the limiting factor for both charging and discharging. Therefore, shorting can have no bad effect.

Paul

PerryBebbington: What does the data sheet say?

Surprisingly, not much. This is the one I am experimenting with.

It says enough! There is a peak current quoted, and a short circuit current, and a note that a short circuit will damage the lead (well, quite, those pins are not going to withstand over 1000A without some melting!)

i don't know of any starter relay that would handle that either... generally you use heavy cables for welding and even that will have duty cycle for cool down. If they discharge to a short, you will only be able to do spot welding while it recharges as the current and voltage will drop quickly... try it and let us know what you find. My welders operate between 80-150 A and even that gets too hot at times.

Paul_KD7HB: I will go out on a limb and suggest the very high ESR is the limiting factor for both charging and discharging. Therefore, shorting can have no bad effect.

Paul

Your are right, https://youtu.be/Ceos88VO6p4?t=508 according to this video, the ESR of that discharging loop is 5.7mohm.

SteveMann:
I have limited experience with supercaps, but I have not seen a max discharge current in the specs. Back in the HV days, we routinely shorted out power capacitors with a screwdriver before working on a circuit.

So, you want to spot-weld your CD’s? Sounds drastic.

If you try this on a 2.7V 3000F supercap with ESR of 0.29mohm ;D

wolframore: i don't know of any starter relay that would handle that either... generally you use heavy cables for welding and even that will have duty cycle for cool down. If they discharge to a short, you will only be able to do spot welding while it recharges as the current and voltage will drop quickly... try it and let us know what you find. My welders operate between 80-150 A and even that gets too hot at times.

Yes, starter relay can typically handle 150A of current, I don't think that's enough for supercap, I have to use mosfet for this.

liyuqihxc: If you try this on a 2.7V 3000F supercap with ESR of 0.29mohm ;D

I'd like to see that....from a distance :o

liyuqihxc: Yes, starter relay can typically handle 150A of current, I don't think that's enough for supercap, I have to use mosfet for this.

Are we talking about the same thing? There’s a starter relay which activates a starter solenoid. The starter solenoid can handle high current... the relay not so much.