The state of the art approaches to estimate the state of health (SOH) and state of function (SOF) of lithium Ion batteries

This paper discusses the commonly used techniques to estimate the state of health (SOH) and state of function (SOF) of lithium ion batteries and their limitations. Factors affecting the health and SOF of the battery are discussed in this paper. The SOH of the battery is mainly represented by the capacity degradation and the increase in the internal resistance. The other indices that could represent the battery´s health are also briefly discussed. The different techniques that are used to estimate the capacity and internal resistance of the battery are discussed along with their limitations. The concept of SOF and its relationship with SOC, SOH and temperature are discussed along with the commonly used techniques to estimate the SOF of the battery. This paper also discusses the limitations in the definition and estimation of the SOF.