The new 18650 rechargeable battery from Fenix not only shines with a maximum capacity of 3500mAh, but in contrasts to previous models with flat head also has the classic plus pole with "dimple", making the rechargeable battery compatible with lights from other manufacturers such as Nitecore. Li-ion type 18650, 3.6V, 3500mAh rechargeable battery. Three-way protection (overheating/overcharging/deep discharge).