12 V On-Board Electrical System, Basic Function - GF54.10-P-1014A
Model All (4xWD)
Model All (CAR)
Overview
This document contains information on:
- General
- Function
- 12V on-board electrical system
- Secondary 12 V on-board electrical system (vehicles for conditionally automated parking or driving)
- Shutoff of 12 V on-board electrical system (vehicles with battery main switch)
General
The 12 V on-board electrical system (A) normally includes all components for voltage generation, voltage regulation and energy storage. The 12 V on-board electrical system (A) supplies the electrical consumers of different systems, such as interior lighting, exterior lighting or engine management, with electrical energy.
Depending on the equipment installed, the 12 V on-board electrical system (A) may be supplemented by a secondary 12 V on-board electrical system (B).
Function
12 V on-board electrical system
On vehicles with a 12 V alternator (1), the necessary electrical energy is generated when the combustion engine is running. This is stored in the 12 V onboard electrical system battery (9).
Vehicles with 48 V technology, hybrid vehicles and electric vehicles do not have a 12 V alternator (1). On these vehicles, the necessary electrical energy for the 12 V on-board electrical system (A) is provided via a DC/DC converter by the 48 V battery or by the high-voltage battery.
Secondary 12 V on-board electrical system (vehicles for conditionally automated parking or driving)
The 12 V on-board electrical system (A) is supplemented by a secondary 12 V on-board electrical system (B), which is fed from the 12 V on-board electrical system (A) in normal mode via a DC/DC converter (5). Electrical energy is stored in the secondary 12 V on-board electrical system battery (7).
To ensure safe operation of the service brake as well as the steering during conditionally automated parking or for conditionally automated driving SAE level 3, the system components required for this in the vehicle are designed redundantly.
In the event of a fault or failure of the regular on-board electrical system, the secondary 12 V on-board electrical system (B) takes over supply of these system components for a defined period of time. This means that the vehicle, whether automatically or by means of driver intervention, can be brought to a safe state, e.g. braked and parked.
Hybrid vehicles and electric vehicles for the Chinese market also have a small buffer battery that ensures the emergency supply for the telematics services communication module.
Shutoff of 12 V on-board electrical system (vehicles with battery main switch)
Using the battery main switch, the user can disconnect the 12 V on-board electrical system battery (9) from the 12 V on-board electrical system (A). In this way, the on-board electrical system battery can be preserved during extended idle time.
The on-board electrical system battery is disconnected via a contactor. This is not opened while the engine timing is performing run-on cooling. This ensures that electrical energy is still available to ensure that the engine is sufficiently cooled.
To prevent a build-up of heat, the on-board electrical system battery must not be cut off when the stationary heater is active.
Example illustration of 12 V on-board electrical system
| Detailed information | |||
| 12 V on-board electrical system with support battery, detailed information | Model 223 with engine 279 | GF54.10-P-1018A |