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Battery Energy Calculator

Calculate the energy stored in a battery and its usable portion.

About Battery Energy Calculator

Energy is the product of charge and voltage, so a 100 Ah 12.8 V battery stores 1.28 kWh. Using nominal rather than peak voltage gives the realistic figure. Comparing batteries on amp-hours alone is misleading across different voltages; watt-hours is the only comparable unit.

Formula

Battery Energy

Energy (Wh) = capacity (Ah) × nominal voltage (V)

nominal voltage
Average voltage across the discharge, not the fully charged value

Worked example

With the default values below, Battery Energy Calculator returns Energy Stored of 1,280.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Capacityminimum 0 Ah
100 Ah
Nominal voltageminimum 0.1 V
12.8 V
Usable depth of dischargeaccepts 0–100 %
90 %
Cells in seriesaccepts 1–200
4

Results

Energy Stored
1,280.00 Wh
Energy Stored
1.2800 kWh
Usable Energy
1,152.00 Wh
Energy per Cell
320.000 Wh
Voltage per Cell
3.200 V

Step by step

  1. 1Values used
  2. 2Battery Energy
  3. 3Energy Stored= 1,280.00 Wh
  4. 4Energy Stored= 1.2800 kWh
  5. 5Usable Energy= 1,152.00 Wh
  6. 6Energy per Cell= 320.000 Wh
  7. 7Voltage per Cell= 3.200 V

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Battery Energy calculated?

Energy (Wh) = capacity (Ah) × nominal voltage (V) Energy is the product of charge and voltage, so a 100 Ah 12.8 V battery stores 1.28 kWh. Using nominal rather than peak voltage gives the realistic figure.

Why does Battery Energy matter?

Comparing batteries on amp-hours alone is misleading across different voltages; watt-hours is the only comparable unit.

What values do I need to enter?

This calculator takes 4 inputs: Capacity, Nominal voltage, Usable depth of discharge, Cells in series. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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