Ammonia cracker..if it don't fit, you must uh...quit.

Aronsson shows his ammonia cracker here.

I extracted some pics from the video:

Looks like the dimensions are approximately 1 cubic foot, this supplies presumably a 5 kilowatt hour fuel cell

The ammonia tank behind the cracker.

And a schematic of the insides of the black box.

There needs to be at least 4 of these crackers for 4 of the 5 kilowatt fuel cells that would be needed for highway driving.  That many fuel cells would be necessary because the electrical discharge on a battery at highway speed is about 20 kilowatts per hour.

Based upon this, I don't think all of this hardware will fit in a car.  The cracker will have to stay off the auto and the hydrogen will have to be compressed at the fueling station before being dispensed to the fuel tank in the car.