The invention relates to a method for thermal conditioning of a battery pack (4), wherein said battery pack (1) comprises a plurality of battery cells (4a, 4b, 4c, . . . ) and forms part of an electric storage system (15), said method comprising a step of executing a ready-to-run function for optimizing the performance of said battery pack (4) during use. Furthermore, the method comprises the steps of: calculating a setpoint temperature (Ts) for the battery pack (4) to reach in order to provide a sufficient level of performance without further thermal conditioning during a predetermined time period (t); and thermally conditioning said battery pack (4) so as to reach said setpoint temperature (Ts). The invention also relates to an arrangement for such a thermal conditioning.