Method for charging a traction battery of a motor vehicle

A method for charging a traction battery of a motor vehicle having an electric traction motor by way of a stationary charging column,

• wherein the charging column has:
• a charging column charging controller for monitoring and controlling the charging process,
• a charging voltage converter for providing a DC charging column voltage fed in in charging lines,
• an insulation tester for testing the electrical insulation of the charging lines with respect to the ground potential, and
• a charging-column-side charging plug,
• wherein the charging voltage converter provides a fixed maximum charging column voltage for charging the traction battery that may be a low voltage value or a high voltage value,
• wherein the motor vehicle has:
• a charging controller for monitoring and controlling the charging process,
• a vehicle-side charging plug,
• the motor vehicle traction battery, which has a technical charging voltage level with the high voltage value,
• a charging voltage adapter, by way of which the charging column voltage is adapted to the technical charging voltage level of the traction battery where needed,
• a protection relay, associated with the charging lines, between the traction battery and the charging plug, and
• an electrical voltmeter, associated with the charging lines, between the protection relay and the charging plug,
• the method comprising the following steps when the charging plugs are connected:
• registering a charging process by way of the vehicle charging controller to the charging column charging controller with the high voltage value as requested maximum charging voltage,
• when the motor vehicle protection relay is open:
• controlling an insulation test, carried out by the charging-column-side insulation tester, by way of the charging column charging controller for an insulation test voltage, which corresponds to the requested maximum charging voltage or to the maximum charging column voltage when the latter is lower than the requested maximum charging voltage,
• measuring the insulation test voltage by way of the voltmeter,
• if the measured insulation test voltage corresponds to a lower voltage value than that of the technical charging voltage level:
• registering a charging process by way of the vehicle charging controller to the charging column charging controller with the low voltage value as new requested charging voltage and setting the charging voltage adapter to a charging column voltage corresponding to the low voltage value.