I've uploaded the EagleCAD schematic & PCB layout files along with some useful ref. info on batteries and desulfators.

The schematic layout is a bit spaghetti like, I'll neaten it up at some point, but it isn't very complex.

I have to add a text file or embed some text in the schematic to explain the operation and discuss the component selection. There are 5 basic blocks:
1) The capacitor bank (Low ESR)
2) The NFET bank (ruggedized for hi pulse currents)

3) The Opto-isolated gate driver for the NFET bank.
4) The reverse voltage tolerant power snubber
5) The fail safe crowbar (for the main fuse) for the snubber lamp.

As noted before, use OFC #12 AWG cabling, two pairs per battery terminal with crimped 1/4" spade receptacles to match the PCB spade terminals. Heavy duty 100A or 200A battery clamps (pictured in files section) are used and the ends of the two pair cabling (per clamp) are soldered right up into the jaws of the clamp to minimize clamp losses.