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Science & Engineering

Battery Runtime Estimator

Estimate battery runtime from capacity (Ah, mAh or Wh), voltage, load (W, A or mA), usable depth of discharge and inverter efficiency.

Your inputs

About 50 % is often advised for lead-acid, 80–100 % for lithium — check the datasheet.

Results

Estimated runtime

8.64 hours

Runtime (h:mm)
8:38
Nominal energy
1,200 Wh
Usable energy at the load
864 Wh

≈Estimate based on the stated model and assumptions

Notes for this result

  • High discharge rates, cold temperatures and battery ageing reduce real capacity (the Peukert effect is not modelled).

What this calculator does

How long a battery lasts depends on its usable energy and the power drawn.

Formula and method

Energy (Wh) = Ah × V (or mAh ÷ 1000 × V); usable = Wh × DoD × efficiency; runtime = usable ÷ load (W)

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Battery capacity: 100
  • Capacity unit: Ah
  • Battery voltage: 12 V
  • Load: 100
  • Load unit: Watts
  • Usable depth of discharge: 80 %
  • Inverter / converter efficiency: 90 %

Results

  • Estimated runtime: 8.64 hours
  • Runtime (h:mm): 8:38
  • Nominal energy: 1,200 Wh
  • Usable energy at the load: 864 Wh

How to read the results

Lead-acid batteries last longer when not deeply discharged; lithium batteries tolerate deeper cycles.

Assumptions and limitations

  • High loads, cold and ageing reduce capacity; Peukert’s effect is not modelled.

These are educational estimates. Electrical, structural and other safety-critical work must comply with local codes and be designed or checked by a qualified professional.

Questions

Why include inverter efficiency?

Converting DC to AC wastes some energy as heat.

Methodology and verification

Result type
Estimate based on the stated model and assumptions
Formula version
1.0
Automated verification
3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

Privacy

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