Electrical system isolation in event of closed-circuit current violation

The following text shows how the power module (PM) behaves

• in the event of different closed-circuit current violations
  
• and logged-on stationary consumer units.
  

The current values used in the illustrations are only to be viewed as tendencies (e.g. between 10 A and 20 A or between 5 mA and 10 mA).

Normal sleep procedure without closed-circuit current violation

Sequence, normal sleep procedure:

• Terminal R off or change of flaps or ZV status
  CAN bus goes to sleep after a few minutes
  
• After 16 minutes, the signal ”CS off” is transmitted by the PM
  the bus is thus woken briefly
  the VA_roof output is shut down
  the bus goes to sleep
  
• After 60 minutes, the VA_body output is shut down
  the VA_body relay drops out
  the PM assumes the closed-circuit current monitoring function
  

Sleep behaviour with closed-circuit current violation after 120 minutes

Sequence in event of a closed-circuit current violation after 120 minutes:

• Terminal R off or change of flaps or ZV status
  CAN bus goes to sleep after a few minutes
  
• After 16 minutes, the signal ”CS off” is transmitted by the PM
  the bus is thus woken briefly
  the VA_roof output is shut down
  the bus goes to sleep
  
• After 60 minutes, the VA_body output is shut down
  the VA_body relay drops out
  the PM assumes the closed-circuit current monitoring function
  
• Closed-circuit current violation (I> 80 mA)
  5 minutes waiting period. In this period, the current is measured by the PM every 1.5 seconds. The electrical system has the option of accepting a normal closed-circuit current in this period. If a current is detected during the waiting period which is OK over a period of 1 minute (codable), the waiting period is started again.
  In the current path shown, the closed-circuit current violation remains at the end of the waiting period.
  
• An entry is made in the fault memory
  the shutdown counter starts for 90 seconds
  the electrical system is isolated briefly
  
• If the closed-circuit current violation is still present
  the shutdown counter is started a second time for 90 seconds
  
• The electrical system is isolated
  

The electrical system is closed again by the following events:

• Change to terminal R or terminal 15
  
• Operation of battery switch
  
• Signal to terminal 15 wake-up line
  
• External charging detection
  
• CAN message on activated statutory consumer units
  

Sleep behaviour with logged-on stationary consumer unit:

• with terminal 0 (terminal R and terminal 15 off)
  
• and excessive closed-circuit current
  

Sequence with logged-on stationary consumer unit:

• Terminal R off or change of flaps or ZV status
  CAN bus goes to sleep after a few minutes
  
• After 16 minutes, the signal ”CS off” is transmitted by the PM
  the bus is thus woken briefly
  the VA_roof output is shut down
  the bus goes to sleep
  
• Stationary consumer unit logs on (in the example at hand 30 minutes after terminal R off).
  The PM permits the log-on provided the battery charge state is still sufficiently high. The consumer unit is entered in a list in the PM.
  If the battery charge state drops during operation of the stationary consumer unit to such an extent that starting capability is jeopardised:
  
  • the telegram Stationary consumer unit off is transmitted on the CAN bus
    
  • the electrical system is isolated after 5 minutes
    
  • and the CC message ”Recharge battery” is issued
    
• Stationary consumer unit logs off (telephone, gearbox)
  Closed-circuit current violation (I> 80 mA)
  5 minutes waiting period. In this period, the current is measured by the PM every 1.5 seconds. The electrical system has the option of accepting a normal closed-circuit current in this period. If a current is detected during the waiting period which is OK over a period of 1 minute (codable), the waiting period is started again.
  The waiting period is normally 5 minutes. If however the telephone or the gearbox is logged on as a stationary consumer unit, the waiting period is 10 minutes.
  In the current path shown, the closed-circuit current violation remains at the end of the waiting period.
  
• An entry is made in the fault memory
  the shutdown counter starts for 90 seconds
  the electrical system is isolated briefly
  
• If the closed-circuit current violation is still present
  the shutdown counter is started a second time for 90 seconds
  The electrical system is isolated
  

Sleep behaviour with logged-on stationary consumer unit:

• with terminal 0 (terminal R and terminal 15 off)
  
• without closed-circuit current violation
  

Sequence with logged-on stationary consumer unit:

• Terminal R off or change of flaps or ZV status
  CAN bus goes to sleep after a few minutes
  
• After 16 minutes, the signal ”CS off” is transmitted by the PM
  the bus is thus woken briefly
  the VA_roof output is shut down
  the bus goes to sleep
  
• Stationary consumer unit logs on (in the example at hand 30 minutes after terminal R off).
  The PM permits the log-on provided the battery charge state is still sufficiently high. The consumer unit is entered in a list in the PM.
  If the battery charge state drops during operation of the stationary consumer unit to such an extent that starting capability is jeopardised:
  
  • the telegram Stationary consumer unit off is transmitted on the CAN bus
    
  • the electrical system is isolated after 5 minutes
    
  • and the CC message ”Recharge battery” is issued
    
• Stationary consumer unit logs off
  In the current path shown, the closed-circuit current is OK after shutdown of the stationary consumer unit.
  

Sleep behaviour with logged-on stationary consumer unit:

• with terminal R
  

With terminal R, the stationary consumer units may only be operated for such a period of time which does not jeopardise starting capability.

If the battery charge state drops during operation of the stationary consumer unit to such an extent that starting capability is jeopardised:

• the telegram Stationary consumer unit off is transmitted on the CAN bus
  
• the electrical system is isolated after 5 minutes
  
• and the CC message ”Recharge battery” is issued
  

Stationary consumer units

The following control units log on and off with the PM as stationary consumer units.

• Trailer Module
  
• Control Display
  
• Light module
  
• A/C control unit
  
• Gearbox control unit
  
• Telephone
  

Trailer Module

The trailer module logs on with the PM for the following functions:

• Sidelights
  
• Parking light
  
• Hazard warning lights
  

Control Display

The control display logs on with the PM as a stationary consumer unit under the following conditions:

• by pressing the volume control button on the audio system controller
  and then operating the controller
  
• or in the event of an incoming call (with telephone switched on)
  

Light module

The light module logs on with the PM as a stationary consumer unit for the following functions:

• Sidelights
  
• Parking light
  
• Hazard warning lights
  

A/C control unit

The A/C control unit logs on with the PM as a stationary consumer unit for the following functions:

• Independent heating
  
• Independent ventilation
  
• Residual heat
  

Gearbox control unit

The gearbox control unit logs on with the PM as a stationary consumer unit under the following conditions:

• Engine OFF
  
• Selector-lever position N
  

Functional sequence:

• The parking gear in the gearbox is held open by a holding magnet
  
• after 30 minutes a CC message is issued to the effect that the parking gear is being engaged
  
• then the parking gear is engaged after 5 minutes have elapsed
  
• the gearbox control unit logs off as a stationary consumer unit
  

If during these 5 minutes one of the following actions is performed

• Operation of selector lever
  
• Opening/closing of driver's door
  
• Unloading/loading of driver's seat occupancy
  

the 30 minutes are started again.

If the battery charge state drops during the restarted sequence to such an extent that starting capability is jeopardised, the time is reduced from 30 minutes to 5 minutes.

If selector-lever position P is engaged after the engine has been switched off:

• the parking gear is engaged
  
• the gearbox control unit does not log on with the PM as a stationary consumer unit
  

Telephone

The telephone (ECE and US) logs on with the power module as a stationary consumer unit for the following function:

• Timer
  

The charging tray for charging the keypad handset is supplied via body consumer unit shutdown for 60 minutes.

Special case, instrument cluster

After the vehicle is stopped (engine off), the value of the outside-temperature sensor is interrogated every 10 minutes for the purpose of determining the outside temperature. No other bus is woken by the instrument cluster for the purpose of interrogating the outside-temperature sensor.

For the purpose of calculating the outside temperature, the coolant temperature is also included by the engine (waste heat from the engine affects the outside-temperature sensor).

The coolant temperature is interrogated by the instrument cluster.

• The CAN bus is woken by the instrument cluster
  
• The coolant temperature is interrogated by the engine control unit
  
• The CAN bus goes to sleep
  
  

Bus wake-up times for determining coolant temperature

The time for interrogating the coolant temperature with bus waking and bus sleeping is below 5 minutes. Thus the sequence lies within the waiting period of the PM.

The instrument cluster does not have to log on with the PM as a stationary consumer unit.