1. The problem statement, all variables and given/known data Hello, long story short: I need to create a model of Li-Ion battery and i'm stuck on calculating the battery equivalent internal impedance. The thing is, I don't know the equation or even how to make one. However, I have a circuit drawing: 2. Relevant equations Values in circuit are calculated by other equations, and I don't think they are relevant here. 3. The attempt at a solution I have nothing to start of except the circuit drawing, so naturaly I don't have any attempts. Well, I tried to draw the circuit with simulink, but values for those blocks are not dinamical. Could someone explain how to calculate or write down an equation for battery equivalent internal impedance Edit: After googling and trying to remember what i learnt from school, I think it should be r =Rseries + Rcycle +1/R_transient_s + 1/R_transient_L Am I right? But Does capacitors don't have any influence for r?