PETZL - ACCU NAO+ Rechargeable Battery for NAO+ Headlamp SIMPLE CHARGING: Simple universal charging via the micro USB port. KNOW IF IT IS CHARGING: Charge indicator on the battery. ALL CLIMATES: Performs well at low temperatures. LIGHTWEIGHT AND FAST CHARGING: The ACCU NAO + only weighs 95 grams and has a recharge time of 6 hours. COMPATITBLE HEADLAMPS: Works with the Petzl NAO+ Headlamp