MAX17048 - Relationship between Battery voltage and State of charge (SOC)
Open-circuit voltage (OCV) of a Li+ battery uniquely determines its SOC. One SOC can have only one value of OCV.
V cell = (OCV - IR drop),Where V cell is a function of OCV, load, temperature, age, time and impedance.
SOC can have many values of V cell , so V cell cannot uniquely determine SOC.