The NiteCore NL166 650mAh RCR123A rechargeable li-ion battery has built in IC protection that will protect against damage due to both low and high voltage. These batteries are designed to perform under high discharge applications. You may charge these batteries over and over for years to come with a rating of more than 500 charge-discharge cycles. This is a button top cell making it easier to use with many flashlights. Rechargeables offer a great value over standard primary batteries. 650mAh 3.7V 2.4Wh. 650mAh 3.7V 18650 Li-ion Rechargeable NL166 Batteries Integrated overcharge & discharge protection circuits 500 charge cycles Certified by CE, UL & ROHS