Lithium Ion 18650 Battery: 3.7V / 2600 mA-hr from 64seconds on Tindie
4 pcs Rechargeable Battery Lithium Battery 3.7V 1800mAh ICR Large Capacity Long Lasting Button Top Rechargeable Battery Li-ion Batteries for LED Flashlight Lamp, 65 * 18mm, Blue | Algopix