Power and current estimation for batteries

The present invention relates to a method and a system for determining a maximum charge current (i max ) or a maximum discharge current (i,in) of an energy storage cell (103) of an energy storage device (102). The method comprises providing a predetermined upper voltage limit (V max ) or lower voltage limit (V min ), and providing a time horizon (t) as a time difference from a present time (t) to a future time (t+t). With a repetition time period (T) different from the time horizon, repeating measuring a present voltage level (V) of the energy storage cell; calculating a voltage difference (V) between the present voltage level and the upper voltage limit (V max ) or the lower voltage limit (V min ); and determining the maximum charge current (i max ) or maximum discharge current (i min ) corresponding to the voltage difference and a model, such that the estimated voltage is within the voltage limits.