SOC (State of Charge)
Definition
Estimate of remaining battery capacity expressed as a percentage of total usable capacity. Analogous to a fuel gauge in vehicles.
Why It Matters
- Critical for runtime prediction and mission planning
- Prevents overdischarge which damages lithium-ion cells
- Accuracy affects user confidence and system reliability
- Requires integration of voltage, current, temperature over time
Common Pitfalls
- Using voltage-only estimation (inaccurate under load)
- Not compensating for temperature effects on capacity
- Ignoring aging effects on capacity (SOC accuracy degrades)
- Not recalibrating SOC periodically with full charge/discharge cycles