2. Recharging by recuperation

The vehicle's kinetic energy is used to recharge the battery by the recuperation. The electric drive is in generator mode, where the electric machine is controlled as a generator and the vehicle is braked. Power is taken from the electric machine, which is then used to recharge the battery.

Charging by the recuperation can be used for

  • traction battery charging (Li-ion, Li-pol, Ni-MH, etc.),
    • HEV, PHEV, BEV,
  • on-board lead acid battery (12 V) charging,
    • especially µHEV: start&stop + ESM (Energy Smart Management).



Driving mode
Power flow in driving mode



Braking mode (recuperation)
Power flow in braking mode



  • During braking, the polarity of the torque changes compared to the drive mode. This changes the polarity of the mechanical power and recharges the traction battery.

  • Driving mode

    • P=Mω=3U_sI_scos⁡φ=U_{dc}I_{dc}

  • Braking mode

    • -P=-Mω=-3U_s I_s cos⁡φ=U_{dc} (-I_{dc})


Change of current polarity on the DC side of the drive (traction battery side)


Motor vs. generator mode for electric synchronous machine with permanent magnets


  • Rated power of the machine in motor and generator mode is practically the same.
  • However, the rated charging current of the cell is about 10 times smaller than the rated discharging current!
    • => Charging power is less than power of the generator or the battery must be oversized in terms of discharge current.
  • Remaining braking torque must be provided by mechanical brakes.
  • Often, recharging power is limited by battery management (BMS), depending on set limits or battery condition (cell disbalancing, temperature, etc.).





    Jeschke, S.: Grundlegende Untersuchungen von Elektrofahrzeugen im Bezug auf Energieeffizienz undEMVmit einer skalierbaren Power-HiL-Umgebung, Dissertation, Universität Duisburg-Essen, 2016
    https://www.hybrid-autos.info