The standard testing method we do in the lab is do the multi-pulse test with the battery at different SOC levels and calculate the voltage change under each C-rate and time duration. To do this online we need model-based methods where we can identify the parameters.

The internal 'resistance-like' parameters' set(s), measured[1] either in time or in frequency (EIS) domain, is a dominant parameter of a lithium-ion battery sustainability, subject to high intermittency and cycling (history)[1,2]. The battery state-of-charge (SOC) serves as a characteristic operational parameter that should be maintained within a safe range[1-3].

1. Online Lithium-Ion Battery Internal Resistance Measurement Application in State-of-Charge Estimation Using the Extended Kalman Filter https://www.mdpi.com/1996-1073/10/9/1284

2. Online Internal Resistance Measurement Application in Lithium Ion Battery Capacity and State of Charge Estimation

https://www.mdpi.com/1996-1073/11/5/1073/htm

3. Combined internal resistance and state-of-charge estimation of lithium-ion battery based on extended state observer https://www.sciencedirect.com/science/article/abs/pii/S1364032120302859

Thank you Ioannis Samaras

Thank you Weihan Li

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