[Temrotec]

The main problem with all these DIY solutions as I see it is that output voltage is fixed. Given the currents vary in great range the voltage drop on the cables also varies much and so the voltage at the car. So either cables need to be very short AND thick (very impractical) AND clamps need to be of very high quality or voltage at the car varies too much for my comfort. Professional PSUs I've seen (gysflash 100-12hf included, according to their manual, which immediately tells me they have quality product) automatically correct output voltages based on cable characteristics and current consumption so voltage at the car stays more or less stable. No pun intended, but I think people considering DIY should know that.

For professional use in the workshop you are right and youshould spend a lot of money. But what about a hobbyist looking around in a forum? Visiting the car dealer instead of buying a PowerMax™, Schumacher™ (US) or Deutronic™, Eltek™ (EU-De) or Gys™ (EU-Fr)could be the best option.

I know that a professional type like a Gysflash won't give the pittfalls of a DIY PSU but the tutorial I've made takes attention of the critical control points to make. Rock solid connections (binding post connected over copper bars (!) and massive chargings cables to connect the car provokes only a minimal voltage drop (about 0.15 VDC) at the clamps running the PSU at 67 Ampere, as proved with some measurements made (see added pictures at the end of the manual) and using a professional, calibrated multimeter. Even the sound level meter used is a higly professional one (= massive overkill for DIY, I know and I know Ohms law regarding the importance of resistance of cables as well).
In practice the described PSU copes very well, not running hot and not dropping the voltage at high currents.

Best regards