Get High-voltage system Guide for Audi RS E Tron Gt 4 Door First Generation (2021-2026)

High-voltage system

Safety regulations

Direct current of up to approx. 800 Volts is present in the high-voltage system.

Please note:

The high-voltage system may also be energised when the vehicle is parked. For example:

›

When the high-voltage battery is being charged.

When auxiliary air conditioning is active.

When the 12 Volt battery is being recharged by the high-voltage battery.

Work on components of the vehicle’s high-voltage system must only be performed when the system is not energised. To achieve

this, the high-voltage system must be de-energised and the mechanic must then check that the system is de-energised. The de-

energisation procedure is performed according to the five safety rules for electrical technology.

These three work steps must be performed:

1

2

3

De-energise the system

Ensure the system cannot be reactivated

Check that no voltage is present

These two work steps are not relevant for high-voltage vehicles:

4

Ground and short-circuit vehicle

5

Cover or shield adjacent live components

Note

Alternating voltage of 25 Volts and above and direct voltage of 60 Volts and above are hazardous to human beings. It

is therefore crucial to follow the safety instructions given in the service literature and Guided Fault Finding, as well as

the warnings displayed on the vehicle.

Note

Always de-energise the system according to the test plan in the vehicle diagnostic tester. The high-voltage system

must only be de-energised and worked on by qualified staff.

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Warning labels

Warning label in motor compartment

The warning labels marked "Danger" identify high-voltage

components or components conducting high-voltage.

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Special warning label for the high-voltage battery

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Warning labels are fitted to the vehicle to indicate the danger caused by electrical current.

These must be observed in all circumstances to avoid endangering users, workshop staff and technical & medical emergency re-

sponse personnel. The general occupational health and safety regulations for work on high-voltage vehicles apply.

Note

Other/additional warning/information labels may be attached to the vehicle, depending on the country.

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Overview of high-voltage components

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High-voltage battery AX2

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High-voltage battery 1 AX2 is bolted on centrally under the vehicle as a component supporting the body. The battery has 33 battery

modules which are fitted on two levels.

The battery housing is connected to the body via a live potential equalisation line. Potential equalisation refers to a suitably conduc-

tive connection that minimises differences in electric potential.

Switching unit for high-voltage battery SX6 is fitted on the high-voltage battery. The battery module control units are fitted on the

modules inside the high-voltage battery. Battery regulation control unit J840 is located in switching unit for high-voltage bat-

tery SX6.

Technical data

Designation

High-voltage battery

Cell modules

33

Cells

198s2p

Weight in kg

Approx. 650

Nominal voltage

Number of battery cells

Energy content in kWh

Maximum charging capacity in kW

Approx. size in mm

726

396 in 33 modules

93

270

2430 x 1670 x 325

If the vehicle is parked for a long period, the charge level of the high-voltage battery is reduced because the 12 Volt battery is auto-

matically recharged. If the charge level of the high-voltage battery goes below 10%, the 12 Volt battery is no longer recharged.

Reference

Additional information can be found in this SSP (refer to article “12 Volt power supply”).

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Operating temperatures

The battery has an operating range between -30 °C and 50 °C.

It is not possible to activate the vehicle’s drive system under -30 °C. Above 60 °C, the power contactors are opened/kept open when

the ignition is on. At temperatures between 55 °C and 60 °C, the current draw of the high-voltage battery is reduced.

High-voltage batteries that are not currently installed in a vehicle may be stored at temperatures between -40 °C and 60 °C.

Cooling

The coolant circuit for the high-voltage battery provides cooling for the battery. The battery modules release heat to the battery

housing via a layer of thermal grease.

The coolant in the coolant circuit for the high-voltage battery flows through heat sinks that are bonded to the battery housing with

thermal conductive adhesive.

Coolant temperature sender 1 for high-voltage battery G898 and coolant temperature sender 2 for high-voltage battery G899

measure the temperature of the coolant upstream and downstream of the high-voltage battery.

The coolant in the high-voltage battery is circulated by the coolant pump for high-voltage battery V590.

If the low-temperature cooling circuit for the high-voltage battery does not provide sufficient cooling, it is possible to cool the cool-

ant additionally using the refrigerant circuit (this takes place via the heat exchanger for high-voltage battery).

At low temperatures, the high-voltage battery can be heated up while charging via the high-voltage heaters.

Reference

Additional information can be found in this SSP (refer to article “Coolant circuit for high-voltage battery”).

Battery modules

A battery module is made up of 12 pouch cells and the battery module control unit. Each of these cells has a nominal voltage of

3.65 V and a capacity of 66 Ah.

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Note:

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For cells connected in series, the voltages are added together; for cells connected in parallel, the capacities are added together. In

the 6s2p circuit of the module, the nominal voltage of the module is 22 V, and the module capacity is 132 Ah.

Control units for battery modules

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A battery module control unit is fitted on every cell module. The battery modules control unit has the following functions:

›

Measuring the voltage of six cells

Reading signals from two module temperature sensors and one onboard temperature sensor

Passive balancing (max. 100 mA)

The battery modules control unit communicates with high-voltage battery control unit J840 via a twisted-pair cable bus.

The battery modules control unit cannot be renewed individually; it must be renewed together with the battery module.

Module circuits and numbering for the lower battery level

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The modules are numbered from 1 to 33, beginning with the negative battery terminal; the positive terminal is number 33. In oth-

er words, the numbers go from negative to positive potential.

Module circuits and numbering for the upper battery level

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The second level contains modules 18, 19 and 20, and the high-voltage battery fuse.

Switching unit for high-voltage battery SX6

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The switching unit is the divider between the high-voltage battery and the vehicle’s high-voltage system. It incorporates the follow-

ing components:

›

Controller for measuring current and voltage

Fuses for the high-voltage cables (front and rear)

Current sensor (Hall sensor)

Protective relays for high-voltage positive and high-voltage negative sides

Pre-charge protective relay with 30 ohms pre-charge resistance

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Switching order of the protective relays when the high-voltage system is switched on:

›

High-voltage positive - vehicle front end,

High-voltage positive - vehicle rear end,

High-voltage negative - pre-charge,

High-voltage negative.

The protective relays are opened in reverse sequence of the switching order; only if triggered by a crash are they all opened at the

same time.

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Battery regulation control unit J840

Battery regulation control unit J840 is fitted in switching unit for high-voltage battery SX6 and performs the following functions:

›

Monitoring the high-voltage battery

Controlling the temperature conditioning of the high-voltage battery

Controlling the coolant pump of the high-voltage battery

Event memory (storing and displaying entries)

Monitoring the charge level of the high-voltage battery

Monitoring the charge level of the cells

Calculating the capacity of the cells/battery

Calculating battery ageing

Insulation resistance monitoring

Monitoring the current

Switching off the high-voltage system in the event of a fault

Controlling the balancing function

Diagnosing the high-voltage battery

Cell balancing

In this example, a cell is 100% charged and the charging procedure is complete. However, the high-voltage battery charge level is

only 92.5 %. Balancing means that this cell is now discharged via a resistor and can thereby continue to be charged until all cells

have reached the same charge level. This allows the high-voltage battery to achieve its maximum capacitance.

To do this, the battery regulation control unit J840 compares the voltages of the cell groups. If cell groups have a high cell voltage,

the battery modules control unit responsible receives the balancing information. After the ignition is switched off, the battery reg-

ulation control unit J840 checks whether balancing is necessary and initiates the process as appropriate. Only the control units on

the sub-CAN are active when this is done. Balancing is performed at charge levels greater than 30%.

Cell balancing takes place passively, meaning that the energy is dissipated as heat via resistors. The high-voltage battery control

unit controls and monitors cell balancing. Cell balancing takes place only by discharging individual cells. Cell balancing starts every

60 minutes after the vehicle is switched off, once the difference in capacity between the cells reaches approximately 2% (120 mAh)

and the charge level of the high-voltage battery is more than 30%.

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Isolation monitoring

An isolation check is carried out by switching unit for high-voltage battery SX6 when the high-voltage system is being switched on/

off, during vehicle operation (every 30 seconds) and during AC/DC charging (every 30 seconds).

This involves measuring the isolation resistance between the high-voltage conductors and the housing of high-voltage battery 1

AX2 with the current battery voltage.

The system detects insufficient isolation resistances in the components and wiring of the high-voltage system. The AC connections

in the high-voltage battery charging sockets and the AC/DC converter in the high-voltage battery charging units are not checked

due to the electrical isolation of the charging socket to the high-voltage system. The switching unit sends the isolation value to

battery regulation control unit J840 for evaluation. If a low isolation resistance is detected, the control unit sends a message to

data bus diagnostic interface J533 via the hybrid CAN. Via the dash panel insert CAN, the diagnostic interface directs the control

unit in dash panel insert J285 to show a message to the driver in the display in the dash panel insert. If the warning is yellow, the

driver can continue driving and the drive system can be reactivated. If the isolation resistance is too low, a red warning is given. The

journey can be completed, but it will not be possible to reactivate the drive system.

Power contactor with boost function J1178

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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:

›

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)

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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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Voltage converter A48

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Voltage converter A48 converts the direct current of one voltage level into direct current of a different voltage level. On the Audi e-

tron GT, the voltage converter is needed in order to make direct-current voltage from the high-voltage battery (approx. 800 Volts)

available in the required voltage levels:

›

400 Volts for the high-voltage air conditioner compressor

12 Volts for the low-voltage electrical system

.

Voltage converter A48 is located over the centre of the front axle.

A voltage converter can convert the input voltage to a higher or lower voltage level; here, the voltage converter takes the input

voltage from the high-voltage battery and converts it into a lower output voltage. In other words, the HV voltage converter serves

as a step-down converter.

As a general rule, the HV voltage converter is set to operate as a set-down converter if:

›

The drive system is activated

The vehicle is being charged

The 12 Volt battery requires recharging

Notes for service and diagnosis

The voltage converter is maintenance-free. If defective, the entire unit must be renewed.

Diagnosis capability:

Adaption/calibration function:

Guided Fault Finding:

Special tools:

Yes

No

Yes

No

Maintenance-free:

Yes

Note on specified values for voltage converter A48

Input voltage

Output voltage Continuous current output

Peak current output Power output

HV voltage converter

800 V to 12 V

420 V ... 870 V 9 V ... 16 V

420 V ... 870 V 430 V

240 A

13 A

290 A

16 A

3.5 W

5.3 W

800 V to 400 V

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Charging unit 1 for high-voltage battery AX4

When charging with alternating current, the charging voltage for the Audi e-tron GT first needs to be converted into direct-current

(DC) voltage. The high-voltage battery cannot receive AC voltage. This is done using the high-voltage charger, which has a power

rating of 11 kW (standard version). The number refers to the electric input power of the high-voltage charger. The high-voltage

charger also contains the charging management system.

The charger is fitted centrally in the front part of the vehicle.

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The input circuit (1) on the mains supply side contains mains filters to suppress interference from and in the mains supply (these

are required by law). The rectifier bridge circuit (2) after the mains filter passively converts the alternating-current voltage (AC)

from the mains supply to direct-current voltage (DC). The step-up converter (3) directly downstream from this keeps the intermedi-

ate circuit voltage in the downstream intermediate circuit capacitor (4) at a constant 400 Volts DC during the charging process in

order to provide the energy for the H-bridge driver circuit (5). The H-bridge driver circuit (5) converts the direct-current volt-

age (400 Volts) to a square-wave alternating-current voltage (AC) with 100 kHz. This is necessary so that the energy can be trans-

ferred via the isolating transformer. The isolating transformer (6) downstream from this galvanically isolates the AC mains supply

from the high-voltage electrical system of the vehicle (DC). To rectify the voltage, a full bridge rectifier (7) is positioned down-

stream of the output side of the isolating transformer (6). A capacitor (8) positioned after the rectifier serves to smooth and buffer

the current.

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Voltage path

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Key

1

2

3

4

5

6

7

8

AC mains input with filter

Bridge rectifier circuit

Step-up transformer

Intermediate circuit capacitor

H-bridge circuit

Isolating transformer

Full bridge rectifier

DC output with high-voltage intermediate circuit capacitor

Notes on diagnosis and maintenance

Diagnosis capability:

Adaption/calibration function:

Guided Fault Finding:

Special tools:

Yes

No

Yes

Maintenance-free:

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Intermediate capacitors

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A capacitor serving as an energy store and a voltage stabiliser may be fitted between HV positive and HV negative in high-voltage

components. In addition, a resistor which discharges the capacitor when the ignition is off is connected in parallel to the capacitor.

When the ignition is switched off, the capacitor on some high-voltage components is actively discharged by a switch and resistor so

that the components are completely de-energised when switched off.

Note

A capacitor is fitted in some high-voltage components to store power. It must be discharged when the system is de-

energised. You should therefore always de-energise the system according to the test plan in the vehicle diagnostic

tester as this takes the discharging times into account. The high-voltage system must only be de-energised and worked

on by qualified staff.

Additional information can be found in this SSP (refer to article “High-voltage battery 1 AX2”).

Power contactors

The power contactors open immediately if:

›

Maintenance connector TW is opened.

The safety computer sends a crash signal via the data bus.

The safety computer sends a crash signal to high-voltage battery isolation igniter via the dedicated wire.

The fuse for power supply to terminal 30c of the power contactors is disconnected or faulty.

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Safety circuit

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Key:

Hybrid CAN

High-voltage wire

Safety circuit

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High-voltage connector

12 Volt connector

The vehicle has five safety circuits.

›

Safety circuit 1 passes through battery regulation control unit J840, maintenance connector TW and switching unit for high-

voltage battery SX6

›

Safety circuit 2 is located within switching unit for high-voltage battery SX6

Safety circuit 3 is in charging unit for high-voltage battery AX4

Safety circuit 4 passes through voltage converter A48 and electrical air conditioner compressor

Safety circuit 5 is located within high-voltage heater (linear) Z189

The safety circuits in the vehicle are ring circuits that pass through the high-voltage components and control units/contact bridges

in the connectors.

They are supplied with a 10 mA current from the 12 Volt electrical system.

If a safety circuit is interrupted, e.g. if a connector is unplugged, data bus diagnostic interface J533 receives a notification from the

relevant control unit. A signal is sent via the dash panel insert CAN directing control unit in dash panel insert J285 to show a mes-

sage to the driver. It is possible to continue driving until the ignition is switched off. It is not possible to reactivate the drive sys-

tem.

Maintenance connector TW

Maintenance connector TW, also referred to as the high-voltage interlock or service disconnect, is located in the centre front of the

vehicle. It is both an electrical connection in the 12 Volt control circuit for the high-voltage battery power contactors and a compo-

nent part of the safety circuit. Unplugging the maintenance connector TW opens the safety circuit and breaks the 12 Volt control

circuit of the power contactors. This provides a redundant safety configuration. The maintenance connector serves to de-energise

the high-voltage system.

Please use the relevant program in the vehicle diagnostic tester to properly open and de-energise the high-voltage system. After

being opened, maintenance connector TW is secured from being switched back on by the padlock T40262/1.

The maintenance connector is also the primary emergency cut-out connection.

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An information label is affixed to maintenance connector TW.

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An additional emergency cut-out connection (also marked with an information label) to interrupt the control current of the power

contactors is fuse no. 12, which is located in the fuse carrier behind a trim panel on the right side of the luggage compartment (no

maintenance flap).

It is marked with a tag.

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Charging

Charging sockets

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The charging sockets for charging the high-voltage battery are located behind the charging socket covers. The charging sockets are

fitted on the fender panel on the driver side and on the passenger side. Both charging sockets are fitted as standard equipment.

The AC charging socket is located on the driver side; the CCS or DC charging socket (depending on the country version) is located

on the passenger side.

The cover can be opened by unlocking the vehicle and pressing on the cover.

If the charging connector is plugged in, the cover cannot be closed.

If one of the two flaps is open, the other is locked. The manual release mechanism is located in the closure plate between the

fender panel and the A-pillar (open the driver door/front passenger door to operate it).

Overview of the charging sockets

Combined Charging System Type 1 (CCS 1 or Combo 1) high-voltage battery charging socket 1 UX4

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This charging socket can be used to charge the high-voltage battery with alternating current or direct current. The DC contacts are

protected by a flap. Communication between the charging station and charging unit 1 for high-voltage battery AX4 takes place via

contacts CP and PE.

Combined Charging System Type 2 (CCS 2 or Combo 2) high-voltage battery charging socket 1 UX4

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This charging socket can be used to charge the high-voltage battery with alternating current or direct current. The DC contacts are

protected by a flap. Communication between the charging station and charging unit 1 for high-voltage battery AX4 takes place via

contacts CP and PE.

Charge de Move (CHAdeMO) high-voltage battery charging socket 1 UX4

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Can be used to charge the high-voltage battery with direct current (DC). Communication between the charging station and charging

unit 1 for high-voltage battery AX4 takes place via the communication contacts.

China DC high-voltage battery charging socket 1 UX4

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Can be used to charge the high-voltage battery with direct current (DC). Communication between the charging station and charging

unit 1 for high-voltage battery AX4 takes place via the communication contacts.

Type 1 high-voltage battery charging socket 2 UX5

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This charging socket can be used to charge the high-voltage battery with alternating current. Communication between the charging

station and charging unit 1 for high-voltage battery AX4 takes place via contacts CP and PE.

Type 2 Mennekes high-voltage battery charging socket 2 UX5

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This charging socket can be used to charge the high-voltage battery with alternating current. Communication between the charging

station and charging unit 1 for high-voltage battery AX4 takes place via contacts CP and PE.

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China AC high-voltage battery charging socket 2 UX5

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Key:

PE

L1

L2

L3

N

Protective earth conductor

Phase 1 AC

Phase 2 AC

Phase 3 AC

Neutral conductor

Control pilot

CP

PP

Proximity pilot

This charging socket can be used to charge the high-voltage battery with alternating current. Communication between the charging

station and charging unit 1 for high-voltage battery AX4 takes place via contacts CP and PE.

In the case of the CHAdeMO and the China DC charging sockets, the communication with the charging station takes place via the

communication contacts, and via the CP and PE contacts on all other versions.

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Function of the charging button

The charging button can be used to release the charging connector and end the charging cycle.

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Lights and their meanings

White:

Charging cable connected

Pulsating

white:

Establishing/terminating communication connection

Pulsating

green:

The high-voltage battery is being charged

Green (con-

Charging cycle completed, target charge level achieved

stant):

Flashing blue: Waiting for charging to be started by a programmed timer

Red (constant): Fault during charging

Charging times

Charging time for direct current (DC)

Charging time for alternating current (AC)

With maximum charging output for up to 100 km (WLTP)

Approx. 5 min.

Approx. 22.5 min.

Approx. 55 min.

Approx. 90 min.

Approx. 125 min.

Approx. 9.5 h

With maximum charging output (5% to ≤ 80 %)

With maximum charging output (5% to ≤ 100 %)

With 50 kW charging output (5% to ≤ 80%)

With 50 kW charging output (5% to ≤ 100 %)

With 11 kW (0% to ≤ 100 %)

Compact charging system

The Audi e-tron GT is supplied with the second generation Audi e-tron charging system. This is located in the motor compartment

in the storage compartment. The operating unit is activated when the Audi e-tron charging system is connected to the AC power

supply. The internal contactors are open in this situation so that the vehicle charging connector is not live. The contactors are only

closed during charging.

A country-specific charging cable for connecting to the vehicle is permanently attached to the operating unit. One country-specific

connection cable with a household plug and one with an industrial plug are also provided for connection to the AC power supply.

Communication with charging unit 1 for high-voltage battery AX4 takes place via contacts CP and PE using a PWM signal.

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Maximum charging level if connected to AC power:

Domestic power socket

1.8 kW (8 A)

11 kW (32 A, single-phase or three-phase)

[8]

Industrial socket

The charging level can be set to 50% or 100%. The operating units are country-specific. Please only use the Audi e-tron charging

system approved for your country.

Charging clip and connector mounting

The charging clip and the connector mounting can, for example, be secured on a garage wall. The operating unit is fitted in the

charging clip and locked in place. When the vehicle is not being charged, the charging cable can be wrapped around the charging

clip and the vehicle charging connector can be placed in the connector mounting.

[8] The charging level is set to 50 % when the system is connected to an industrial socket. The charging level can be increased to 100%. This setting

is maintained until the operating unit is disconnected from the power supply.

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Diagnosis

The operating unit uses the LEDs to indicate detected faults. Fault finding is possible using the vehicle diagnostic tester and the

adapter VAS 611 009.

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High-voltage system for Your Audi RS E Tron Gt 4 Door First Generation (2021-2026)

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