AN ELECTRIC POWER MODULE SYSTEM

An electric power module system () for use in an electrically operated vehicle (), comprising: —a base module comprising a cooling passage for fluid coolant and coolant connections for supplying fluid coolant to the cooling passage, the base module further comprising at least one external electrical connection for power input to and/or power output from the electric power module system, —an add-on module configured to be mounted to and electrically connected to the base module, so that the add-on module, when mounted, can be cooled and powered via the base module. When the add-on module is mounted, the cooling passage is delimited by at least a first delimiting surface provided on the base module and a second delimiting surface provided on the add-on module, so that fluid coolant supplied via the coolant connections of the base module comes into contact with both of said delimiting surfaces.