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 85 %. 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 85 %. 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).
2.1Area 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.






Brake energy regeneration, slow
Voltage sensitive consumers are activated. This refers to consumers that are sensitive to voltage differences where voltage changes can be noticed by the driver. The voltage changes slowly as brake energy regeneration is activated so that the change is not noticeable. Applies to consumers such as headlamps, fog lamps, fan motor and windscreen wipers.

Brake energy regeneration, quick
No voltage or power sensitive consumers are activated. The voltage changes quickly or immediately during brake energy regeneration.

Brake energy regeneration, slowly without discharging
Voltage sensitive consumers are activated. This refers to consumers that are sensitive to voltage and power differences. Applies to consumers such as engine cooling fan motor, preheating elements, connected trailer and blower fan. When voltage and power sensitive consumers are activated, the voltage changes slowly and the alternator voltage is not permitted to be less than 13.2V. This is to prevent the available output from being too low.




Description of an operating cycle

  1. Conventional battery charging. The battery's SoC is approx. 80 % (poorly charged battery) and the system strives to charge the battery up to approx. 85 %. Brake energy regeneration is not permitted. The charge voltage increases (level depending on the battery temperature) so that the battery charges. When the correct SoC is reached, brake energy regeneration is permitted.
  2. Battery not charging. The engine's efficiency is low (the engine's torque is needed to propel the vehicle) and the battery is not charged. The alternator is controlled so that only the vehicle's power consumers are supplied with the necessary current.
  3. Engine braking (brake energy regeneration). The alternator charges the battery with a voltage up to 15.0 V (charges with energy).
  4. The battery produces energy. The engine's efficiency is low (the engine's torque is needed to propel the vehicle). Regeneration of previously stored energy with a fast current output from the battery down to a voltage of 12.4V.
  5. The battery produces energy. The engine's efficiency is low (the engine's torque is needed to propel the vehicle). Regeneration of previously stored energy with a slow current output from the battery down to a voltage of 12.5 V