A power supply system for an electric vehicle drivetrain, the power supply system comprising: a first high-voltage battery unit, a second high-voltage battery unit connected in series with the first high-voltage battery unit, a circuit arrangement having a plurality of high-power switching semiconductor devices connected to the first and second high-voltage battery units (21, 22), an electronic control system configured for controlling operation of the plurality of high-power switching semiconductor devices for: - during a charging mode of the first and second high-voltage battery units (21, 22), routing high-voltage DC received from a vehicle external charging source alternatingly to the first high-voltage battery unit and to the second high-voltage battery unit, with an alternating frequency of at least 100 Hz, specifically at least 500 Hz, and more specifically in the range of 100 - 10 000 Hz, and - during a power supply mode of the power supply system, supplying high-voltage DC from both the first and second high-voltage battery units (21, 22) for driving a vehicle electrical traction machine of the electric vehicle drivetrain, wherein the supplied high-voltage DC has a voltage level corresponding to the accumulated voltage level of the series connected first and second high-voltage battery units (21, 22). a first high-voltage battery unit, a second high-voltage battery unit connected in series with the first high-voltage battery unit, a circuit arrangement having a plurality of high-power switching semiconductor devices connected to the first and second high-voltage battery units (21, 22), an electronic control system configured for controlling operation of the plurality of high-power switching semiconductor devices for: - during a charging mode of the first and second high-voltage battery units (21, 22), routing high-voltage DC received from a vehicle external charging source alternatingly to the first high-voltage battery unit and to the second high-voltage battery unit, with an alternating frequency of at least 100 Hz, specifically at least 500 Hz, and more specifically in the range of 100 - 10 000 Hz, and - during a power supply mode of the power supply system, supplying high-voltage DC from both the first and second high-voltage battery units (21, 22) for driving a vehicle electrical traction machine of the electric vehicle drivetrain, wherein the supplied high-voltage DC has a voltage level corresponding to the accumulated voltage level of the series connected first and second high-voltage battery units (21, 22). - during a charging mode of the first and second high-voltage battery units (21, 22), routing high-voltage DC received from a vehicle external charging source alternatingly to the first high-voltage battery unit and to the second high-voltage battery unit, with an alternating frequency of at least 100 Hz, specifically at least 500 Hz, and more specifically in the range of 100 - 10 000 Hz, and - during a power supply mode of the power supply system, supplying high-voltage DC from both the first and second high-voltage battery units (21, 22) for driving a vehicle electrical traction machine of the electric vehicle drivetrain, wherein the supplied high-voltage DC has a voltage level corresponding to the accumulated voltage level of the series connected first and second high-voltage battery units (21, 22).