Get High-voltage Safety Guide for Volkswagen Touareg SUV Second Generation (2010-2018)

High-voltage Safety

The increasing electrification and hybridisation of drive concepts is leading to greater use of high-voltage systems

in vehicles.

What does high voltage mean?

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Vehicles with high-voltage systems (HV) are fitted with components that work with voltages above 60V direct

voltage or 25V alternating voltage. Some of the components in these vehicles require a high level of electrical

power. The high-voltage systems in vehicles work with direct voltages of up to 650V and very high peak currents.

What dangers are involved in working with high-voltage

systems?

All movements in the human body are initiated by electrical control mechanisms. All muscle reactions, like your

heart beat or eyes winking, are controlled by electrical stimulation. These electrical stimulations are conducted

inside the body via nerve pathways in a similar way to currents in electrical circuits. 

If you touch live high-voltage components, the current can flow through you body. Even with direct currents above

approximately 30mA, temporary heart pulse disturbance can occur depending on how long the current flows

through the body. At even higher currents in the body, serious internal burns occur and in some cases ventricular

fibrillation can result. 

If the two poles of an electrical system are short-circuited, there is a risk of arcing. This can cause serious external

burns on the human body and electro-ophthalmia of the eyes.

Safety precautions

The risk of contact with live high-voltage components must be ruled out. 

Only specially qualified personnel may perform work on the high-voltage system. In addition to the colour coding

and warnings given on labels on the components, there are technical safety measures.

The exact safety equipment used depends on the vehicle. In the following section, basic safety aspects are

explained without looking at the special installation situation in a vehicle.

Please refer to the workshop literature for which safety equipment is fitted in a specific vehicle.

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The electrical isolation of the high-voltage system and 12V onboard supply

Purpose

The strict isolation of the high-voltage system and 12V onboard supply should prevent unintentional short-circuits

with the vehicle earth. This isolation of the high-voltage system from the body earth is also called electrical

isolation.

How it works

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To achieve this isolation, the high-voltage system has

its own equipotential bonding. The high-voltage

system and the 12V onboard supply are electrically

isolated from each other so that there can be no

accidental short-circuit and thus a flow of current to

the body earth.

12V onboard supply

High-voltage system

While the circuit in the 12V onboard supply normally runs via the vehicle earth, all high-voltage components have

two wires with which their electrical circuit is formed. There is no connection to the body earth.

High-voltage isolation with ignition “off”

Task

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The simplest way to deactivate the high-voltage

system and disconnect the high-voltage system from

the high-voltage battery is to turn the ignition key to

the “Drive Off” position. 

Depending on the vehicle equipment, this can also be

done with an “Engine Off” button (e.g. with Keyless

Entry).

How it works

The ignition lock or the “Engine Off” button is used as switches with which the electric circuit to the protective relay

of the high-voltage system is interrupted (see next page). This opens the protective relays and the high-voltage

battery is disconnected from the high-voltage system. The high-voltage system is de-energised after a short time.

The high-voltage battery itself and the high-voltage lines up to the protective relay are still energised, however.

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High-voltage Safety

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The protective relays in the high-voltage system (high-voltage contactor)

Purpose

The high-voltage battery is connected to the high-voltage system. Each of the high-voltage connections has its own

protective relay that can interrupt the circuit. The protective relays therefore have the task of connecting the high-

voltage system in the vehicle (contactor closed) or disconnecting it (contactor open).

How it works

The protective relays are switched only toher by

the high-voltage system. If the contactors are de-

energised, they open and the high-voltage battery is

disconnected from the high-voltage system in the rest

of the vehicle. The command to open can be

triggered by different situations. If you switch off the

vehicle and remove the ignition key, this will also

High-voltage system deactivated

open the contactors and activate the other safety

systems.

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High-voltage system activated

High-voltage battery

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Battery management

Protective relay (contactor)

Power electronics

Electric motor/generator

Air conditioner compressor

Safety information

Work on the high-voltage system may only be performed by qualified Volkswagen high-voltage

technicians. The instructions in the service literature must be followed strictly for the proper and safe

use of the special high-voltage tools.

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The pilot line

Purpose

The pilot line is a completely independent safety system. It determines whether all high-voltage components are

correctly connected to the high-voltage system. The pilot line is a low-voltage system.

Design

The pilot line connects all high-voltage components.

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The system checks whether the high-voltage

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connections of the components incorporated in the

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pilot line are correctly connected. Depending on the

vehicle, various connector types are integrated into

the pilot line.

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2

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Pilot line continuous

High-voltage battery

Battery management

Maintenance connector

Pilot line connectors

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2

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4

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Connections for high-voltage components

How it works

The pilot line circuit is interrupted as soon as a high-

voltage contact on a high-voltage component is

disconnected, e.g. when a high-voltage component is

replaced. The same happens when one of the pilot

line connectors is disconnected. As soon as the high-

voltage system detects that the pilot line is interrupted

at just one point, the protective relays are opened

and the high-voltage battery is isolated from the high-

voltage system.

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Pilot line interrupted

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High-voltage Safety

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Maintenance safety

Purpose

The high-voltage system normally has a maintenance connector near to the high-voltage battery as an additional

safety feature for de-energising the high-voltage system when work is carried out in the workshop. If you unlock the

maintenance connector and pull it out of its fitting, the contactors and the high-voltage battery will be disconnected

from the high-voltage system. In addition, the maintenance connector may also contain the main fuse for the high-

voltage battery (e.g. Touareg Hybrid 2011).

Set-up using Touareg Hybrid 2011 as example

The maintenance connector is under an orange-

coloured cover near to the high-voltage battery in the

electronics box. It is an electrical bridge between the

battery modules of the high-voltage battery and, at

the same time, part of the pilot line. The maintenance

connector needs to be unlocked before it can be

pulled out of its fitting. 

The appearance of the connector may vary and

depends on the vehicle type.

How it works

Unlocking the maintenance connector interrupts the pilot line and thus deactivates the high-voltage system. The

protective relays (contactors) open and disconnect the high-voltage system from the high-voltage battery.

Disconnecting the maintenance connector will electrically isolate the battery modules of the high-voltage battery

from each other. Only the actual battery modules are now still live with a reduced voltage.

Safety information

Make sure you follow the three basic rules of high-voltage safety: 

1. De-energise the high-voltage system. 

2. Secure the vehicle against reactivation. 

3. Check that/determine whether the high-voltage system is de-energised.

This procedure is known as certified de-energisation and may only be performed by a high-voltage

technician.

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Crash safety

Purpose

Deactivation of the high-voltage system and thus the de-energisation of the high-voltage system is very important

for occupant protection in accidents, the safety of rescue personnel and safety in accident vehicles that have been

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brought in for repair. For this reason, the high-voltage safety is linked to the crash detection system via the airbag

control unit.

How it works

Crash detected

As soon as the airbag control unit detects an accident

and deploys the belt tensioner or airbags, the battery

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regulation control unit is instructed via the CAN data

bus to open the protective relays.

If just the belt tensioners are deployed (single-stage

crash deployment), it will be possible to close the

contactor again by switching the ignition on and off

again. The belt tensioners and airbags are deployed

in the second crash stage. The contactors can then be

Airbag control unit

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closed again only with the VAS tester.

Data bus diagnostic interface

Control unit for battery regulation

CAN message

High-voltage system

Safety information

Always refer to the respective guidelines for rescue services for information on the different ways to

deactivate the high-voltage systems in crashed vehicles.

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High-voltage Safety

Safety during external charging

If the vehicle has a charging contact for external charging, protective relays are also fitted in the charging circuit of

the high-voltage system. They only connect the high-voltage battery to the charging contacts if the system detects

that the charging contact has been connected and a voltage is present. The charging procedure can also be

performed safely in rain or if the contacts have been exposed to moisture.

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Monitoring the insulation resistance

The battery regulation control unit transmits a test voltage while the high-voltage vehicle is in use. The test voltage

is 500V and has a very low current. It is therefore not dangerous for humans.

If all high-voltage components and wires are correctly

insulated and shielded, the control unit calculates and

compares the previously set total resistance of the

high-voltage system. If the insulation of a wire is

damaged externally, for example, by a vermin bite,

the insulation resistance will change. 

The control unit detects an insulation fault due to this

change in resistance. Depending on the severity of the

fault, various messages can appear in the vehicle

instrument cluster.

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Damaged high-voltage lines are always replaced. The insulation cannot be repaired due to the

insulation resistance monitoring system. Slight deviations in the resistance, for example, due to damp

weather with salt ingress, can cause an insulation fault again.

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Warning stickers

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During work with high-voltage vehicles, different warnings draw attention to the special characteristics of the high-

voltage technology.

Warning notices related to high voltages

Do not switch on. 

Work on high-voltage system in progress

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Caution, hazardous voltage!

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Caution! 

Parts carrying high voltages.

Before starting work, perform certified de-energisation of the high-

voltage system.

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Hazardous voltage!

Electric shock if touched! 

De-activate high-voltage system.

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Caution! High-voltage battery

Incorrect handling can cause injuries.

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High voltage

Risk of explosion

Chemical burns and eye injuries

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High-voltage Safety for Your Volkswagen Touareg SUV Second Generation (2010-2018)

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