Racing car fuel tank sponges - GIF

[hemmjo]

That's why they are called Fuel Cells...

The term Fuel Cell, is no longer sufficient to define what we are talking are talking about. Originally it was a tank designed to keep fuel from spilling during a crash and prevent or minimize fire risk. They contained a flexible bladder to contain fuel if tank is deformed in a crash. The also contained an absorbent material to minimize sloshing around as described.

These days Fuel Cell is often used when talking about a device that converts hydrogen to electricity. More correctly Hydrogen Fuel Cell, but more often that not the Hydrogen part is left out.