capacitor discharge rate

You can't tell unless you know what the resistance is. If you know the resistance, then

V(t) = Vo * exp(-t/R/C)

and

I(t) = V(t)/R

so

I(t) = Vo * exp(-t/R/C) / R

where Vo is the initial voltage across the caps.

If you can measure how long it takes for your voltage to get down to 1/2 the original voltage, you can figure out the resistance; it will be

R = t/(ln(2)*C)

plug that back into the I(t) expression.

For example, if it takes 0.1 second to discharge down to 2.5 volts from a

R = 0.1/(ln(2)*.75) = 0.192 ohms

Then, the initial current will be I = 5/0.192 = 26A, and after 0.1s, will be 13A.

Not necessarily, Most SCRs can withstand at least 10 times their rms current rating in a discharge application such as this. If you have the data sheet look at the peak one cycle surge current rating

what's the resistance and inductance of the whole setup? (the limiting factor is probably the resistance of the capacitors)

Bye. Jasen

Is there a way to calculate the amps a capacitor dischages through a short?

I have a "spot welder" made up of five large 150,000 uf (5 volt)computer capacitors in parallel, which are charged to up using a 1 to 5 volt supply and dischaged through a SCR to 2 beefy probes. The purpose is to spot weld terminal tabs on batteries in place of soldering them on.

How many amps are being produced across the terminal probes, ususally spaced

thanks Jim