These small coin sized batteries have become the backbone of Raider bartering across the ruins. Each one carries a small amount of electricity that can be used to power the various items found in the ruins.
Importantly, the can also be used to power the Protein Spinnners, meaning that they are one of the few items that has an almost fixed price. After all, everyone needs to eat.
There are also larger batteries that carry a charge equivillent to 10 cells. These are commonly callled Bats to differentiate them from Cells.