Abstract: A method for predicting a state-of-power, SoP, of an electric energy storage system, ESS, comprising at least two battery units electrically connected in parallel. The method includes obtaining operational data from the at least two battery units of the ESS during operation of the ESS; computing the state-of-power of the ESS based on the obtained operational data and by using an algorithm based on a system-level model of the ESS, wherein the system-level model of the ESS takes into account on one hand each one of the at least two battery units of the ESS, and on the other hand at least one electrical connection between the at least two battery units, and wherein the system-level model of the ESS further takes into account a dynamic parallel load distribution between the at least two battery units.