EleCanada
Energy storage

Battery energy calculator

Convert a battery pack's nominal voltage and rated amp-hour capacity to nominal Wh and kWh. The result is not a usable-capacity or runtime estimate.

Calculation inputs

Battery rating inputs

V

Use the nominal voltage and rated capacity for the same battery or pack level.

Ah

Enter ampere-hours, not milliampere-hours. Divide mAh by 1,000 before entering it.

Example values are loaded from the NRCan battery-capacity example: 12 V and 80 Ah. Replace them with the same pack's nameplate values.

Enable JavaScript to calculate. The formula and scope remain below.

Nominal battery energy

Enter nominal pack voltage and rated capacity.

Nominal energy does not mean the full rating is available for discharge. Reserve, depth of discharge, temperature, ageing, load and conversion losses can change usable energy.

What it calculates

This calculator converts a nominal voltage and an amp-hour rating at the same battery or battery-pack level into nominal energy. It reports both watt-hours and kilowatt-hours.

Use the manufacturer's nominal voltage and rated capacity for the same complete battery or pack. Do not combine an individual-cell voltage with a whole-pack capacity.

Method and examples

Nominal energy in watt-hours is Wh = V × Ah. Kilowatt-hours are kWh = Wh ÷ 1,000.

A 48 V, 100 Ah pack has 4,800 Wh, or 4.800 kWh, on this nominal arithmetic basis. A 14.8 V, 10 Ah battery has 148 Wh, or 0.148 kWh.

Limits and interpretation

This is a nameplate-style conversion, not a battery test. It does not model usable capacity, depth-of-discharge limits, reserve, charge/discharge rate, temperature, ageing, internal resistance, inverter efficiency or load runtime.

Use the battery-runtime calculator when you already know available energy at a defined AC or DC boundary. Do not treat this nominal result as evidence that a battery or inverter can supply a continuous load or starting surge.

No battery selection, safety approval, transport classification or installation decision is provided.

Common questions

Can I enter milliampere-hours?

Convert mAh to Ah first by dividing by 1,000. The input is labelled Ah to keep the voltage-times-capacity units explicit.

Is nominal kWh the same as usable kWh?

No. Usable energy depends on the battery's permitted operating range and conditions. The nominal conversion does not apply a depth-of-discharge or efficiency factor.

Can I use this result as runtime?

No. Runtime also requires a load and a defined energy boundary. Use the battery-runtime calculator with available energy and load power.

Battery runtimeEstimate runtime from available energy and load.Electrical relationshipsSolve DC quantities, convert AC power/current, compare PF current ratios, or relate balanced wye voltages.PV string voltageCalculate known-string Voc at supplied temperatures.

Sources

Transport Canada, Shipping and importing lithium batteries and lithium battery-powered devices, “Calculate the amount of energy (Wh) rating.” The Canadian guidance states `Wh = nominal voltage × Ah` and advises contacting the manufacturer when the rating is uncertain. Its transport context is not generalized to battery selection or installation.

Natural Resources Canada, Photovoltaic Systems: A Buyer’s Guide, “Technical Note: Battery Capacity Rating,” printed page 30: gives 12 V × 80 Ah = 960 Wh and explains that available capacity is below the nameplate rating. The usable-capacity and discharge guidance is not folded into this nominal conversion.

Report a problem or suggest a source. Calculation values are not included automatically.