A free battery calculator with three modes: find runtime, required capacity or maximum power draw. Choose Li-ion, LiPo, NiMH, lead acid, alkaline or custom cells and work in mAh, Ah, Wh, mA, A or W. Add multiple devices from a built-in library of Arduino boards, sensors, LEDs and motors. Advanced options cover temperature, aging, efficiency, series/parallel cells, C-rate and safety margin. Save configs, no signup.