Model card: Power SoC

Module: src/nous/estimators/power.py

Backlog: BL-027

Inputs

• Battery voltage and current from PowerSubsystem.sensor_obs().
• Cell temperature from ThermalSubsystem.sensor_obs() (for the Peukert correction).

Outputs

Estimate with point = {soc_pct, voltage_v, current_a} and a 3x3 covariance.

SLA

• Update latency: under 1 ms per call.
• Covariance bound: SoC sigma <= 2 percentage points at >20% SoC, <= 5 percentage points below 20%.

Known failure modes

• Coulomb counting alone diverges over multi-day runs; the voltage update bounds the drift but introduces noise. Calibrate against a full charge/discharge cycle on the actual cell.
• Cold-cell behaviour deviates from the Peukert correction below 0C; the model card explicitly does not bound the error there.