It probably only needs to be 20 amps. I am doing 12vdc 20a now on my car better it is a bit slower than 22vdc 20a from a transformer. I need battery power at a Black Smith group gathering in a State Park the area where they meet and demonstrate for 3 days has no electricity so it needs to be battery power. I raise my car hood put 2 alligator clamps on my car battery to run the induction heater to heat 1/2" solid steel rods red hot. Induction heater will not get as not as coal I need an extra 400 degrees F.
I have worked on 24 volt trucks. It is hard to get the two batteries to charge together when you have 12 and 24 volt loads and only a 24 V alternator.
It is possible to add a second 12V alternator to your car. Connect "ground" to +12. This way each battery will have a alternator.
OR
I can get negative 12V alternators. That will give you + and - 12V. You then connect your heater from -12 to +12 and it will think it is running on 24V.
All that requires you adding an alternator/generator and rerouting the fan belt. But the project is then just a mechanacial project.
We might be able to park 2 vehicles next to each other then connect batteries in series with jumper cables. Then connect negative alligator clip to 1 car battery and connect positive alligator clip to positive of the other car battery to power the induction heater. I can try this at home first it should work fine as long as someone does not open a door that bumps the other vehicle and shorts out.
Good idea. Keep an eye on the battery voltage(s). One of the batteries will go down first and you don't want to fully discharge it. That depends if the cars are running or not.