Updated
Electrical
Battery Capacity Calculator
Convert Ah, Wh, and mAh by voltage, estimate runtime for a device load, size a battery bank for a target number of hours, and estimate charging time using charger amps and efficiency.
Battery Capacity, Energy, Runtime and Battery Bank Planning
Enter battery specs and load values to get energy capacity, usable energy, estimated runtime, recommended bank configuration, and charge-time estimates.
Ah becomes energy only after voltage is included. This tab converts capacity and shows total energy for multiple batteries.
Runtime uses usable energy (DoD and efficiency). For inverter-powered AC loads, efficiency is often below 100% and surge loads can reduce runtime.
Bank sizing starts from energy: required Wh = load W × hours. It then adjusts for efficiency and DoD, and suggests series/parallel counts based on your battery voltage and target system voltage.
Charging is not perfectly linear because current tapers near full. The charge factor accounts for inefficiency and taper time (typical values are 1.10–1.30 depending on chemistry and charger behavior).