Open Circuit Voltage of Lithium-ion batteries for energy storage in DC microgrids

Rechargeable batteries, particularly Lithium-ion ones, are emerging as a solution for energy storage in DC microgrids. This paper reviews the issues faced in the characterization of the Open Circuit Voltage (OCV) of a Lithium-ion battery, starting from the problem of OCV measurement and ending with the modeling of OCV hysteresis. An accurate OCV modeling is necessary for a reliable estimation of the internal battery states, such as State-of-Charge and State-of-Health. These state variables are useful for a better control and a more efficient utilization of the energy storage system in the microgrid. We also compare with experiments two models that account for the hysteresis in Lithium-Iron-Phosphate batteries.