21700 has become the standard format

Just a few years ago the 18650 format was the unquestioned standard for battery packs. The picture has changed: leading cell manufacturers are gradually winding down 18650 lines and shifting capacity to the 21700 format.

The reasons are clear. The larger can holds more capacity per cell — modern 21700s reach 5000 mAh and beyond. At the same time, lower internal resistance and better heat dissipation deliver higher energy density at pack level.

For battery design this means fewer parallel groups at the same capacity and fewer connections — a simpler, more reliable pack and easier thermal management.

At ServiceLine we work with A-grade 21700 cells — Samsung 50S, EVE, Tenpower, Molicel — and we see the transition first-hand: the vast majority of new projects today are built on 21700.