Voltage supply

Voltage supply

The power management is the most important component of the energy management. The power management is software in the engine control module. The power management regulates the alternator voltage with the engine running.
The intelligent battery sensor helps to reduce consumer units or switch them off completely as required, even while the engine is running. This consumer unit shutdown lowers the power consumption in critical situations. This prevents the battery from discharging.

Brief description of components

The following components for power supply are described:

Intelligent battery sensor

The intelligent battery sensor (IBS) evaluates the current quality of the battery. The IBS has its own control module. The IBS is part of the battery negative terminal. The IBS regularly measures (cyclically) the following values:

• Battery voltage
  
• Charge current
  
• Discharge current
  
• Temperature of the battery
  
  

Alternator

The alternator is connected to the DME control module across a bit-serial data interface.
The alternator interchanges data with the DME control module across a bit-serial data interface. The alternator provides the DME control module with information, e.g. type and manufacturer. This enables the DME control module to adapt control of the alternator to the alternator model fitted.

System functions

The following system functions are described:

Voltage supply

The power supply of the DME control module is as follows:
the ignition and starting switch signals terminal 15 On to the DME control module (separate pin). In response, the DME activates the DME main relay. The DME main relay thus supplies other inputs of the DME control module with voltage. The Digital Engine Electronics main relay also ensures the power supply for other control modules and components. For memory functions, the DME control module still requires a sustained power supply via terminal 30. The earth connection of the DME control module is ensured via a number of pins that are connected to one another in the control module. The battery voltage is monitored continuously by the digital engine electronics control module. With a battery voltage of less than 2.5 Volts or greater than 24 Volts, a fault is entered. The diagnosis only becomes active 3 minutes after engine start-up. This means that the effects of the starting operation or starting assistance on the battery voltage are not detected as faults.

Activation of the alternator

For the alternator with bit-serial data interface, the following functions are implemented in the digital engine electronics control module:

• Switching the alternator on and off on the basis of defined parameters
  
• Specification of the maximum permitted power consumption of the alternator
  
• Calculation of the input torque for the alternator from the power consumption
  
• Control of the reaction of the alternator with addition of high power consumers (load-response function)
  
• Diagnosis of the data line between alternator and DME control module
  
• Storage of any faults that occur on the alternator in the fault memory of the DME control module
  
• Activation of the charge control lamp in the instrument cluster via bus connection
  

The main function of the alternator is also ensured in the event of interruption of the communication between the alternator and DME control module. The following fault causes are distinguishable by the fault code memory entries:

• Overheating protection:
  the alternator is overloaded. For safety reasons, the alternator voltage is reduced until the alternator has cooled down again (the charge control lamp does not light up).
  
• Mechanical fault:
  the alternator is mechanically blocked. Or the belt drive is defective.
  
• Electrical fault:
  defect in the exciter diode, interruption in the excitation coil, overvoltage due to defective regulator.
  
• Communication failure:
  defective cable between DME control module and alternator.
  

An interrupt or short circuit in the coils of the alternator cannot be detected.

No liability can be accepted for printing or other faults. Subject to changes of a technical nature