Power contactor with boost function J1178, or HV booster, acts as an energy distributor and also increases the direct-current volt-
age from 400 Volts to 800 Volts (hence the term “booster”). This is necessary, for example, if the vehicle is going to be charged at
a public charging station with 400 Volts. Power contactor with boost function J1178 has a power output of 50 kW in the standard
version, or 150 kW as optional equipment.
Several high-voltage components are connected to the HV booster; it therefore serves as an energy distributor. The components
connected to the HV booster include:
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Charging unit 1 for high-voltage battery AX4
High-voltage heater (linear) Z189
Voltage converter A48
High-voltage battery 1 AX2
Electric drive control unit for front axle J1234
Power contactor with boost function J1178 is located below voltage converter A48 and above the power electronics, centred over
the vehicle’s front axle.
Voltage conversion (boost function)
684_435
The voltage conversion (400 Volts to 800 Volts) operates on the principle of a charge pump. The basis of how it works is a series
connection of the capacitor. It is important to note that the voltage converter can only double the direct-current voltage.
Power contactor with boost function J1178 acts as an energy distributor and, when necessary, as a voltage doubler if the DC charg-
ing station is able to supply a 400 Volt current.
Power contactor with boost function J1178 is designed to be maintenance-free. Opening the components is strictly prohibited.
Notes for service and diagnosis:
Location in the vehicle:
Removing and installing:
Diagnosis capability:
Adaption/calibration function:
Guided Fault Finding:
Special tools:
Front of vehicle
Entire component
Yes
No
Yes
No
Maintenance-free:
Yes
Dismantling level:
None, only complete component. Dismantling strictly prohibited!
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