French researchers have announced a prototype of an 18650 sodium-ion battery. If you’ve bought a powerful LED flashlight, a rechargeable battery pack ... there are some design tradeoffs.

Some of the nuances of battery pack design can be found in this guide to building packs from the standard 18650 cells.

according to a news release published by PR Newswire that detailed the power pack's unveiling. "We are excited to introduce the world's first 18650 potassium-ion battery," Alexander Girau ...