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Power Supply and Bus Systems - Overview - e85 BMW Z4 E85/E86

Body Electrical 13 illustrations ~483 words

Model: E85

Production: All

The purpose of the Power Supply System is to safely deliver the required voltage and amperage to vehicle systems. The power supply system includes vehicle ground points and fuses. The power supply system includes the following components

Scheme 279

Scheme 279: Power Supply
  1. Battery
  2. Monitored Battery B+ Cable (New System)
  3. Fuse Box
  4. Fuses
  5. Ground Points
  6. Alternator
  7. Jumper Cable Point

Battery

The Battery is located in the luggage compartment right hand side. Battery power is split with one leg routed through a 250 amp fuse to the main fuse box behind the glove box. The other circuit is sent through the BST and to the new monitored B+ cable that supplies power to the starter and alternator.

Depending on equipment on the vehicle either a 50AH, 70AH or 80AH battery is installed.

Scheme 280

Scheme 280: Battery

Scheme 281

Scheme 281: Battery Cable Routing

Monitored B+ Cable

The Monitored B+ Cable is a mutli-strand aluminum cable with a cross section of 80 mm 2.

The aluminum cable is sheathed with an insulating layer and surrounded by a detecting shielded cable. An outer insulating sheath covers the entire assembly.

Scheme 282

Scheme 282: Monitored B+ Cable

The Monitored B+ cable is routed underneath the vehicle from the battery box along the floor pan to the engine compartment jumper cable point. The B+ cable is attached to the underside of the body with two different style clips. The cable is protected with plastic shielding. (Description of cable monitoring is found in Safety Systems.)

Scheme 283

Scheme 283

Scheme 284

Scheme 284

Scheme 285

Scheme 285

Fuse Box And Fuses

The Fuse Box is located behind the glove box and accessible by removing the glove box door and underdash panel. The fuse box contains blade type fuse and special fuses for higher amperage consumers. Relays are located on both the front and back sides of the fuse box.

Scheme 286

Scheme 286: Fuse Box And Fuses

Scheme 287

Scheme 287: Ground Points

Alternator

Depending on country and equipment the vehicle is equipped with different output alternators.

Battery charging voltage varies according to ambient temperature. At lower temperatures, the battery is less susceptible to boiling over and can be charged at higher voltages. At high temperature the charging voltage is reduced to prevent loss of the battery electrolyte through evaporation.

The DME controls the output rate of the alternator.

Scheme 288

Scheme 288: Alternator

Jumper Cable Point

The Jumper Cable Point is located in the engine compartment on the left side at the firewall. The jumper cable point is the junction for the Monitored B+ cable and the alternator and starter.

Scheme 289

Scheme 289: Jumper Cable Point

Scheme 290

Scheme 290

The bus system of the E85 is based on the E46. The E85 uses the K-Bus, PT CAN and the D-Bus of the E46. These busses have been modified to accommodate additional components and systems. In addition to these bus systems, the byteflight bus has been carried over from the E65. The byteflight bus is a fiber optic bus used for the ASE system.

Scheme 291

Scheme 291: Bus Systems