The battery cable is fitted with an electrically conducting shield, which is insulated against the body and against the battery cable. The shield consists of a low-impedance metal mesh. A cable exits from each end of the shield, i.e. at the safety battery terminal in the luggage compartment and at the battery ground point in the engine compartment. The adapter cable at the safety battery terminal is connected to the right B-pillar satellite, the adapter cable in the engine compartment to the left B-pillar satellite. In order to minimize the danger of fire in the case of damage to the cable, the battery cable is monitored by the following satellites:
The battery safety terminal is installed in the positive lead (charge wire) from the alternator just in front of the positive terminal of the battery: The cable ends in a tapered plug. If the monitoring of the battery cable determines a short circuit, the safety battery terminal is triggered by the right B-pillar satellite. This switches off the alternator and the fuel pump.
It also deactivates the starting motor load circuit. The engine can no longer be started.
The interrupted alternator line can be replugged provisionally to restart the engine. In this case, however, the battery terminal isolation function is no longer available as the priming cap has already been ignited. The priming cap and alternator line must then be replaced.
The two ends of the shield are fed to the A/D converter input from the left B-pillar satellite and the right B-pillar satellite. The left B-pillar satellite contains a resistor that is connected to the shield and the ground. The right B-pillar satellite contains a resistor of the same size that is connected to the shield and the supply line of the satellite. The low-impedance shield and the resistors of the same size mean that around half the voltage supply of the satellite is applied at the A/D converters (5 V). In the event of a fault, different measurement values result, as shown in the following table.
|
Test result left B-pillar satellite |
Test result right B-pillar satellite |
State |
|
|
Battery cable: OK |
approx. 5 V |
approx. 5 V |
Battery cable: Break |
approx. 0 V |
approx. 10 V |
Battery cable: Short circuit to ground |
approx. 0 V |
approx. 0 V |
Battery cable: Short to positive |
approx. 10 V |
approx. 10 V |
If an interruption or short circuit occurs, the relevant fault memory entry is stored in the right B-pillar satellite.
Note:
The battery cable is only cut by the safety battery terminal in the event of a short circuit. if, for example, the outer insulation of the battery cable is damaged but the shield has no ground connection, the following case could occur:
Moisture (e.g. rain) can gradually reduce the voltage. A short circuit to ground is detected, but the safety battery terminal is not triggered. In the fault memory of the right B-pillar satellite, the entry: ”Battery cable: implausible test result” is set. The airbag warning lamp is also activated.
All work on the airbags must be carried out with the battery disconnected!
Connect and disconnect all BYTEFLIGHT control modules, sensors and generators only with the battery disconnected!
If a fiber-optic cable on the BYTEFLIGHT bus has to be repaired, it must be borne in mind that there may only be one join in a fiber-optic cable. If there is already a join due to a door connector, the fiber-optic cable must not be repaired. In the case of a defect, the fiber-optic cable must be replaced!
Code and program all BYTEFLIGHT control modules before initial startup: the control modules (satellites) contain vehicle-specific data!