Model | 963, 964 |
with code E5T (ADR type class EX/II, incl. AT) | |
Model | 963, 964 |
with code E5U (ADR model class EX/III, including EX/II and AT) | |
Model | 963, 964 |
with code E5V (ADR model class FL, including EX/II, EX/III and AT) | |
Model | 963, 964 |
with code E5X (ADR type class AT) | |
Model | 963, 964 |
with code E5Z (Accessories, ADR) | |
Model | 963, 964 |
with code E9D (Pre-installat. for bipolar battery circuit breaker) | |
Model | 963, 964 |
with code E9E (Provision, ADR, without chassis shielding) |
Location
Shown on model 963 without code C7T (Integral rear area) |
A33 | Battery disconnect switch control unit (BESO) |
W54.21-1431-03
On vehicles with standard rear area, the battery disconnect switch control unit is installed below the starter battery in front of the compressed-air reservoirs of the brake system in the direction of travel.
Shown on model 963 with code C7T (Integral rear area) |
A33 | Battery disconnect switch control unit (BESO) |
W54.21-1430-04
On vehicles with integral rear area, the battery disconnect switch control unit is installed on the inside of the left longitudinal frame member above the rear axle.
Tasks
To evaluate the positions of the cab battery disconnect switch (S30) and the chassis battery disconnect switch (S31).
To disconnect the on-board electrical system from the battery if the cab battery disconnect switch or chassis battery disconnect switch is operated.
Structure
Control electronics
Bistable relay for disconnecting the on-board electrical system from the battery
Function
The battery disconnect switch control unit evaluates the positions of the cab battery disconnect switch and the chassis battery disconnect switch via the input signal. If the cab battery disconnect switch or chassis battery disconnect switch is actuated, the battery disconnect switch control unit disconnects the on-board electrical system from the battery.
Even before disconnecting the on-board electrical system from the battery, it sends a message on the exterior CAN (CAN 1) for further processing, in which it is announced that the on-board electrical system will be disconnected from the battery. Among other things, the engine management (MCM) control unit (A4) initiates the switching-off of the engine due to this message. The on-board electrical system is disconnected via a bistable relay integrated into the battery disconnect switch control unit.
The bistable relay is actuated 800 ms after the battery disconnect switch control unit has detected operation of the cab battery disconnect switch or chassis battery disconnect switch. The tachograph (TCO) (P1) is still supplied with voltage from the battery disconnect switch control unit via a separate pin.
Redundant to the message on the exterior CAN, the battery disconnect switch control unit sends a pulse width modulated signal to the following control unit via a direct line:
Cab sensor and actuator module (SCA) control unit (A7), vehicles of model generation 1 without code Z3L (Single SAM instead of SAM cabin and SAM chassis)
Single signal acquisition and actuation module (SSAM) control unit (A7a), vehicles of model generation 1 with code Z3L (Single SAM instead of SAM cabin and SAM chassis)
Advanced signal acquisition and actuation module (ASAM) control unit (A7), vehicles of model generation 5
If the battery disconnect switch control unit detects that the cab battery disconnect switch or chassis battery disconnect switch has been operated, it changes the duty cycle of the pulse width modulated signal from 50 % to 75 %. Depending on the equipment installed, the cab sensor and actuator module control unit, the single signal acquisition and actuation module control unit or the advanced signal acquisition and actuation module control unit detects that a disconnection of the on-board electrical system is initiated.