> adding a fuel cell to an ice

For anyone as confused as I was: https://en.wikipedia.org/wiki/Fuel_tank#Racing_fuel_cell

It's one of my pet peeves that in the racing world "fuel cell" means "hardened fuel tank" instead of "solid state fuel oxidising power generator".

Particularly as fuel cell engines have been researched.

For electric conversions, Lithium iron phosphate batteries are popular in part because they're less likely to catch on fire if you puncture them, short them, overcharge them, or otherwise abuse them.

Or have a battery that's shaped like a fuel tank? Maybe you won't get the same range as battery all over but it's prob enough for most people?

Not sure why you're being downvoted. In the future when battery energy densities are a multiple of current gen we'll definitely have gas tank form factor batteries for restomods.

Today the range would be pretty bad though, but probably fine for a classic car grocery getter or trailer/show queen.

That's actually something I'm working on right now. I'm trying to convert a Mazda RX-8, which has a weird gas tank that goes up and over the drive shaft. I think I can get about half my battery back where the gas tank was (which is right under the back seats).

I'm not sure where all the rest are going to go, but probably most will be in the engine compartment somewhere.

I could also use the space where the muffler was, but I'd have to make sure there's enough weight in the front of the car to offset it.

I think the bigger concern is fire protection, which is already a solved problem with fuel cells. Shouldn't be too different for batteries.

You're probably get an awful range out of a fuel tank shaped and sized battery pack.

I suspect the aversion to a more blocky shape (higher volume/surface-area ratio), has to do with heat dissipation, which if I recall correctly, improves with surface-area.

EDIT: hence the flatter/thinner batteries we see in EVs.

That actually mostly doesn't matter for most batteries. Most EV batteries are actively cooled/heated with fluid moving inside. So the heat dissipation occurs in the radiator for the battery, not at the surface of the battery. We see flat batteries because sticking the battery at the bottom of the car helps with weight distribution and handling.