Not necessarily. They can use capacitors instead. And the battery is only engaged when accelerating or braking. The car runs mostly on the fuel cell in steady s

Not necessarily. They can use capacitors instead. And the battery is only engaged when accelerating or braking. The car runs mostly on the fuel cell in steady state operation. Those are just assumptions. There's no reason why you can't you reduce them to the point where they are non-factors. It's possible they go away completely, for instance if you use thermochemical production of hydrogen or store hydrogen in metal hydrides. As I said previously, you don't need to perfectly match batteries on efficiency. If fuel cells get close to batteries, it's enough for them to succeed. The rest can be made up by a combination of lower upfront costs and light weighting.