eBike Battery Cells - What does 18650 mean?

[Anton]

Batteries used in current generation e-bikes are made with lithium-ion cells. The cells look like a giant AA batteries.

There are two commonly used sizes:

• 18650 (18mm diameter, 65mm length, 0 means it’s a cylinder), and
• 21700 (21mm diameter x 70mm length, 0 cylinder).

18650 is most common because a standard bottom bracket is about 70mm wide, so the 18650 cells can fit laterally into a case about that wide, though they’re usually arranged longitudinally.

There are three types of common li-ion cell, Nickel, Cobalt, and Magnesium and the different chemistries of each have different characteristics. The main companies that make cells are Samsung, Panasonic, Sanyo, LG, and maybe a couple more.