Battery State of Charge (SOC) Calculator
Compute remaining state of charge using nominal capacity, initial SOC, and coulomb-counted amp-hours, with optional temperature adjustment.
For engineering estimation only. Validate against battery management system readings before making operational decisions.
Examples
- Nominal 200 Ah pack, 90% initial SOC, 60 Ah discharged, 95% temperature correction ⇒ 57.00% SOC
- Nominal 100 Ah pack, 40% initial SOC, -10 Ah net (charging), no correction ⇒ 50.00% SOC
FAQ
How should I measure the net amp-hours?
Integrate current over time using a calibrated coulomb counter or battery management system log, treating discharge as positive and charge as negative to align with the calculator's convention.
What if I only know energy in kWh?
Convert energy to amp-hours by dividing by the nominal voltage (Ah = kWh × 1000 / V) before using the calculator, or pair this tool with a pack-level energy tracking model.
Why include a temperature correction factor?
Available capacity shrinks at low temperatures. Applying a derating factor derived from laboratory characterization keeps reported SOC aligned with the deliverable energy in current conditions.
Can the calculator output exceed 100%?
No. The logic clamps the final percentage between 0% and 100% to avoid reporting impossible values even if measurement noise would otherwise push the result beyond physical limits.
Additional Information
- Positive net amp-hours represent energy withdrawn since the initial snapshot; negative values indicate net charging.
- The temperature correction scales the coulomb-counted SOC to reflect capacity reduction at low temperatures when a derating factor is known.
- Results are clamped between 0% and 100% to reflect physical SOC limits while preserving deterministic rounding.