System Overview

System overview

General
The brake energy regeneration system enables the use of kinetic energy in a more efficient way. When the driver brakes the vehicle or releases the accelerator pedal and the vehicle is engine braked, the vehicle's kinetic energy is recycled and stored in the vehicle's battery. An alternator converts the vehicle's kinetic energy, via the driveline, into electricity, which charges the battery more under those conditions (when it is free). When the driver depresses the accelerator again, the alternator charges the battery less than normal or not at all. The vehicle then receives the energy that was previously stored in the battery back again.
As the alternator charges less, less force is required to rotate the alternator, which reduces the load on the engine, which reduces the energy demand and which thereby can also reduce fuel consumption. Fuel consumption can be reduced by approx. 1-3 %.
In vehicles with normal conventional battery charging, the system always strives to charge the battery to a 100% charge level (State of Charge (SoC)). When the battery is fully charged, it cannot take any more energy. In order for the battery to take more energy, during engine braking for example, the battery cannot already be fully charged. The charging system therefore strives to retain the battery at a SoC of about 80 %. This makes it possible to charge the battery with energy and reuse the energy from the battery.

Caution! If a fully charged battery (100 % SoC) is placed in the vehicle, the system will reduce the battery's SoC to around 80 %. For vehicle's with the brake energy regeneration function and battery monitoring sensor, this is completely normal.

In order for the battery to be sufficiently receptive to charging for this function, the battery's temperature must be between + 5 °C - + 55 °C. At temperatures below, respectively, above this interval, brake energy regeneration is not permitted and the system will then apply conventional charging.




The image shows how the system strives to maintain the battery's SoC and at which temperature and SoC the brake energy regeneration function is permitted.
1. State of charge (SoC).
2. Area where brake energy regeneration is permitted.
3. Parameter of how the system strives to maintain the battery's SoC with regard to the battery's temperature. Above 55 °C charging of the battery does not occur, in principle. This is to prevent, for example, overheating.
4. Battery temperature.
5. Area where the system applies conventional charging.




The system consists of the following:
- The Engine control module (ECM) is the main module for this function. The control module sends information to the Alternator control module (ACM) about what charge voltage the alternator is to maintain.
- Alternator control module (ACM) with charge regulator. The control module is controlled by the Engine control module (ECM).
- Battery monitoring sensor. In order for this function to work, the battery's status must be thoroughly calculated and monitored. The vehicle is therefore equipped with a battery monitoring sensor.
- Battery.
- Central electronic module (CEM). If alternator control does not work correctly for any reason, the Central electronic module (CEM) takes over control of the alternator from the Engine control module (ECM). Charging is then conventional.
The sensor on the battery's negative pole indicates that the vehicle has a battery monitoring sensor.
A battery monitoring sensor is always found on vehicles with the automatic start/stop of the engine function. See: Design and Function - automatic start/stop of the engine.
For information about the alternator, see: Design and Function - Alternator