Simulink Capacity Estimator Block

Hello All,

I am trying to estimate Capacity of an LFP Cell with 20Ah Nominal Capacity. I am using the Battery Capacity Estimator Block (Least Squares) and Capacity Estimator Block (Kalman Filter) for the same. I have attached Pictures of the same with the parameter values and the resulting graph. As ypu can see from the graph, the capacity is increasing from it's initial value. This cannot be the case as i am applying repeated WLTP Cycle to the battery. Cany anyone let me know the reasons for the same and how to rectify it?

Answer 1

[Xiangchun]

Hi Gokul,

The parameters for these capacity estimation blocks (whether Kalman filter or least squares) need to be fine tuned to the battery system and sensors you are working with. For example, the variance of current measurement for the Battery Capacity Estimator (Least Squares) as shown in the pictures shared seems pretty high. A 11.3 variance suggests 3.4 A standard deviation for current measurement sensor connected with a 20 Ah cell under WLTP cycle. A deviation of 3.4 A is 17% of 1C current for a 20 Ah cell.

Here is an example on how Battery Capacity Estimator is used for SOH estimation Estimate Battery State of Health Based on Capacity Fade - MATLAB & Simulink (mathworks.com).

Here is the documentation page the provides more descriptions on the parameters for the Battery Capacity Estimator (Least Squares) block. Battery capacity estimator using least-squares algorithms - Simulink (mathworks.com).

Best wishes,

Xiagnchun