Development tests on the Mercedes-Benz GLC F-CELL drive unit in Kirchheim-Nabern; starting tests in freezing conditions with the drive unit tilted at different angles. In order to ensure the safety of the vehicle as a whole, more than 500 individual tests are undertaken as part of the testing programme for each new model at Mercedes-Benz. In the case of electric vehicles, a range of further drive system-specific tests are added to the standard test procedure. Special cold-starting procedures have been devised for use at icy temperatures as low as minus 25 degrees Celsius, to ensure that the frozen system starts as quickly, efficiently and sparingly as possible. Such tests are extremely time-consuming, as the unit needs to go into the climatic chamber for about 12 hours after every start in freezing conditions in order to cool down from the operating temperature reached, before a new start test can be launched.