Best Flashlight Batteries? LBF 18650 & 21700 Tested! Best Flashlight Batteries? LBF 18650 & 21700 Tested! Today, I’m testing the LBF 18650 (3200mAh) & LBF 21700 (5000mAh) 3.7V Li-ion cells to see if they're suitable for flashlights and if their built-in USB-C charging & powerbank features perform as advertised. 👉 Buy here (affiliate link): https://amzn.to/41k0DZR