Lithium Ion Battery - Cell Format
The vast majority of commercially available battery packs for electric bikes are comprised of 18650 size cells. These cells were first developed by Panasonic in 1994 and quickly became the preferred standard around the world.
In more recent times, Panasonic has worked with the brilliant Tesla organization to develop their preferred ‘higher capacity’ 21700 size cells.
This is fast becoming the preferred standard.
18650 Cells Vs 21700 Cells
Lithium ion cell names are based on their physical size.
18650 Cells are 18mm in diameter and 65mm in length.
21700 Cells are 21mm in diameter and 70mm in length.
Note: Tesla now refer to the 21700 cells as 2170 cells (dropping the final zero)
21700 Cells - Tesla preferred format
An increase in the cell size from 18650 to 21700 allows for a better internal structure which increases the electrode area yielding a higher capacity output.
So, you can get more power with a smaller number of cells!
According to the Journal of The Electrochemical Society research, in a battery pack using the 21700 Tesla format you need 33% fewer cells than the 18650 format to obtain the same capacity.
This basically means that for two battery packs with the same ‘physical size’ the one containing 21700 cells will have a higher capacity – so for ebikes, giving you more discharge time or greater range (distance).
For our customers, we have released some high capacity models to enhance our current range and many of them use the Tesla preferred 21700 format.
Check out our range of high capacity batteries for electric bikes: