The Lithium-ion 18650 battery 3600mAh 3.7v is a lithium-ion cell classified by its 18mm x 65mm size, whichis slightly larger than a AA battery. They're often used in flashlights, laptops, and high-drain devices due to their superior capacity and Discharge rates.
Flashlights, electronics, laptops, vaping and even some electric vehicles use the 18650s. Tesla uses 7180 of these batteries. Many high lumen flashlights use the 18650 or the even larger 21700. Laptops and other electronic devices use one or more 18650’s and have recharging electronics built-in. 18650’s are also used in vaping (smoking) devices.
18650s are generally Lithium-Ion batteries. If you are familiar with electronics you can change out some battery packs manually, but be careful – using the wrong type of 18650 or using it incorrectly can cause a fire.