Wavelet based relative state of health estimation for lithium-ion batteries

It is of great important to obtain the states of the batteries in the storage system in Electric Vehicle, wind, solar power and so on. Among these states, the State of Health (SOH) is particularly important and drawing more and more attention. This paper proposes the wavelet based relative SOH (rSOH) estimation method, especially for the battery storage systems where battery cells are connected in serials. With the rSOH, the fading differences in the battery string can be obtained, which is very useful for battery balancing. By taking advantage of the wavelet decomposition, the battery voltage is decomposed into several layers and the characteristics of the relationship between the decomposed signals and the rSOH is analyzed. The wavelet based rSOH estimation method is then proposed and analysed. The experimental validation is carried out and the rSOH estimation results is proved to be effective.