What's going on in your first paragraph? How did we get from spaceflight to cars?
Without bothering to read these comments, my understanding is that fuel cells are bad for cars but good for spaceships. Batteries win on energy per volume, but lose on energy per mass. Also, fuel cells can store energy for a longer period of time, but that is relevant to the outer system, not for Mars.
Batteries win on energy per volume, but lose on energy per mass.
No, the issue is power density. Fuel cells win over batteries in terms of energy per mass but lose in terms of power per mass and power per volume. Fuel cells are still an order of magnitude or so behind batteries in terms of deliverable power. This is why they are best suited to applications that require power drain for an extended period of time without the possibility of recharging.
It's difficult to directly compare batteries and fuel cells, though, because in the fuel cell the actual f...
Epic work, it's always fascinates me when author explores the topic so deep, that doesn't know where to begin, so finally starts with the whole history of the universe or the existence of human race.
http://waitbutwhy.com/2015/08/how-and-why-spacex-will-colonize-mars.html