Nowadays, lithium-ion battery technology is widely employed in a lot of applications. The state of charge (SOC) is one of the most crucial parameters to be estimated since it ensures working in a safe range and identify the available energy. Several methods for SOC estimation rely on the knowledge of the open circuit voltage (OCV) curve. The latter is highly dependent on the battery temperature, so for a proper SOC estimation, it is important to know and model how the OCV changes with temperature. In the literature, the effect of temperature on the OCV is mostly considered through lookup tables, and correcting factors applied to the OCV curve at a reference temperature. On the other hand, the variation law of the OCV curve as a function of the battery temperature is not well characterized. In this work, based on an experimental campaign, the dependency on temperature was analyzed. Finally, a model was developed and validated.