Battery Energy

E = V × Capacity

Calculator

Result
—

Formula

E = V × Capacity

Description

Battery energy in watt-hours represents the total amount of work a battery can deliver and is calculated by multiplying the nominal voltage by the capacity in amp-hours. This metric allows fair comparison between batteries of different voltages and chemistries. For example, a single 18650 lithium-ion cell at 3.7V and 3Ah stores 11.1Wh, while a 9V alkaline battery at 0.5Ah stores only 4.5Wh despite its higher voltage. To convert watt-hours to kilojoules, multiply by 3.6 (since 1Wh = 3600J).

Variables

  • E — Energy in watt-hours (Wh)
  • V — Nominal battery voltage (V)
  • Capacity — Battery capacity in amp-hours (Ah)

Practical Notes

Nominal voltages by chemistry: alkaline 1.5V, NiMH 1.2V, Li-ion 3.7V, LiFePO4 3.2V, lead-acid 2.0V per cell. Energy density (Wh/kg) varies widely: lead-acid 30-40, NiMH 60-80, Li-ion 150-260, lithium polymer 100-200. Aviation regulations limit lithium batteries to 100Wh for carry-on without approval.

Related Formulas

Battery Runtime Battery Loaded Voltage Battery Charge Time Battery Self-Discharge Battery Temperature Derating Cell Balancing Current

Need more features?

Save calculations, import telemetry data, simulate battery discharge, and collaborate with your team.

Try the App