This work is focused on an easy-to-handle approach for estimating the residue power and capacity of a lithium-ion cell during operation. For this purpose, an earlier presented lumped parameter electrochemical battery model is employed. By means of the parameters accounting for the cathode capacity and the electrolyte conductivity, the cell degradation is successfully reproduced. Moreover, the method enables the distinction of capacity fade due to impedance rise and due to active material loss. High discharge rates together with the correlated self-heating of the cell enable a model-based quantification of SEI and electrolyte contributions to the overpotential.