Reducing fossil fuel consumption requires efforts on the improvement of energy storage technologies. The Li-ion cell is the only technology that allows to do that in the most efficient ways. Bat-man is a novel technology that provides very accurate diagnosis of lead acid batteries. The purpose of the thesis is to understand and predict the behaviour of the Li-ion batteries. To do this, in absence of a real battery to charge and discharge, a Simulink model is built for the simulation. This model is a current controlled voltage generator and has high accuracy but also high complexity because of the presence of 3 RC groups.