7.9 Energy efficiency at fast charging7.9.1 Purpose The purpose of the energy efficiency at fast charging test is to determine the battery system behaviour and the energy efficiency at different fast charging levels. For high-energy battery systems, the energy efficiency also at fast charging of the used battery system has a significant influence on the overall vehicle efficiency. This test applies to high-energy battery systems only. 7.9.2 Test procedure The test shall be performed with battery systems at RT, 0 °C and Tmin and three different fast charging levels (1C, 2C and Ic,max). After thermal equilibration and conditioning of the DUT by a standard cycle, the DUT first shall be discharged via a standard discharge followed in the next step by a fast charge with a starting current of 1C, 2C and Ic,max. The charge rate, the maximum charge current Ic,max and the minimum ambient test temperature Tmin shall follow the requirements delivered by the supplier.The test sequence shall be performed as specified in Table 25. Table 25 — Test sequence energy efficiency at fast charging test