[scythe]

Hydrogen as a sole technology is going to keep eating that 2-3x energy penalty versus batteries regardless of storage tech. Hydrogen IC has even worse efficiency than FC. The only exception would be if hydrogen mining yields world-changing amounts of the stuff.

As a hybrid technology, it has a case. If you run 80% of the time on battery and 20% of the time on hydrogen at 50% RTE, you burn 120% of the fuel. But if you weigh 30% less, you could end up saving energy. The up to 60% efficiency of the fuel cell is losing energy as heat, and people like to run the heater, so some of that energy isn't lost in appropriate climates. And of course, refueling is faster for road trips. The best system weight is probably for the experimental direct-ammonia alkaline membrane fuel cells, assuming it's possible to stabilize them, because ammonia fuel systems (about 100 psi) are much simpler than hydrogen systems (about 10000 psi!). So there's a little room left for the hydrogen fans. But it's fundamentally a battery-powered car most of the time.