It is welding at over 1000 amps (copper spot welding is hard). To change it to a welder the the red wires go through an inductor core, and high voltage diodes get added. I’m including a zip of the EagleCad for the welder. The board is laid out with a bunch of choices. Right now the controller is external, but it is setup to have onboard TI MSP430 or TI Launchpad controller (which allows inexpensive embedded processor (MSP430), ARM processor, or DSP Processor board to control it). If it is a welder you only need 4 sets of transistors and diodes, but bigger / more wires.
I also have 2 DC-DC converter boards that I have been working on and am hoping the latest circuit board (this week) will be the go forward, stable. 1 buck converter optimized for ~24 volt input ~14 output 25 amps. Tested from 3-30 volts in and 2-input voltage out. 1 boost converter optimized for ~13 volts in ~16 volts out at 8 and 16 amps. Tested 3-16 volts in up to 24 volts out.
All of these are open source, and it is time for me to get ready to do some moving. - finished moving