AC out to DC output 90 amp flux core wire welder
You never stated the voltage on the capacitors. My guess is you used one with too low of a voltage reading and/or wrong polarity when you hooked up the Capacitor.  You only needed to use one capacitor with a minimum of 22000uf 45 volt (75 surge) and better to use a Single phase 200a 1600v bridge inverter. You never noted a leak down resistor and if you didn’t have one on it, you need one or it still hold a charge!