Nowadays, batteries are always more important in our lives especially in automotive field where they are the key point of innovation. In this scenario it is necessary to check how good the battery is. The aim of this project is to evaluate the State of Charge (SoC) and the State of Health (SoH) of a lead acid 12V battery; the first one indicates the remaining charge of a battery while the second is a measure of its aging. The two parameters are strictly related: an old battery has a low SoH, this implies a derating of its capacity and a consequent different behaviour of SoC.