In this paper, the study and the modeling of a lithium-ion battery cell is presented. The battery testing system used to obtain the data to be elaborated is designed and developed by using a programmable electronic load and a programmable power supply. This dedicated laboratory equipment can be used to apply charging/discharging cycles according to user defined current profiles. The battery modeling and the parameters identification procedure is carried out. Finally, the model is exploited to implement a state of charge estimation suitable in the case of different dynamic load inputs.