Here are the key steps I would recommend for lithium-ion battery SOH estimation using BMS board data:
- Perform a full charge/discharge cycle: Fully charge the battery using the constant current, constant voltage method recommended by the manufacturer. Then fully discharge it at a moderate C-rate, recording voltage continuously.
- Analyze discharge curve shape: The shape of the discharge curve can indicate loss of capacity and increased internal resistance. Compare to a fresh battery to identify signs of aging.
- Calculate Coulombic efficiency: Integrate the charge/discharge curves to calculate capacity charged and discharged. Divide discharged capacity by charged capacity to obtain Coulombic efficiency. A lower efficiency indicates capacity loss.
- Conduct open circuit voltage test: Measure open circuit voltage (OCV) after charges and discharges once the battery has relaxed. Compare OCV to manufacturer benchmarks for that state of charge to identify capacity fade.
- Perform internal resistance test: Use current interrupt or DC pulse techniques to isolate and quantify internal resistance. Higher resistance is correlated with capacity fade and impedance growth.
- Validate with full reference performance test: Occasionally conduct a full capacity, power capability, and efficiency test using a battery cycler that provides an absolute reference compared to the previous baseline.
Remember that the specific steps may vary based on the BMS and battery technology you are using. Always refer to the manufacturer’s guidelines and documentation for accurate testing procedures. Additionally, ensure that your testing complies with safety standards to prevent any risks during the assessment.