PETZL - ACCU 4 ULTRA Rechargeable Battery for ULTRA RUSH / ULTRA VARIO ULTRA HIGH CAPACITY: Lithium-Ion technology offers high capacity (5200 mAh) with reduced weight . ADAPTIBLE: Can perform well at low temperatures. ENERGY GUAGE: Energy gauge allows monitoring of battery's charge level. RECHARGE TIME: 6 hours. WORKS WITH YOUR HEADLAMP WALL CHARGER: Charges with the wall charger included with ULTRA VARIO and ULTRA VARIO BELT headlamps.