Impact of dc-dc Converters on Li-ion Batteries

Name: Sven De Breucker

• Prof. dr. ir. Johan Driesen (promotor)
• Prof. dr. ir. Geert Deconinck (mede-promotor)

This work investigates the interaction between dc-dc converters on the one hand and batteries on the other hand. As far as battery research is concerned, the focus is on phenomena with relatively large time-constants ranging from seconds to hours and small current ripples.  Conversely, the frequency at which dc-dc converters operate ranges from afew to tens or even hundreds of kHz. The goal of this research is to investigate the impact of these large, high-frequency current ripples on the parameters of the battery. These battery parameters include the battery capacity, the energy content, the State of Charge dependent charge and discharge resistance as well as the State of Charge dependent Discharge and Regen power. In order to allow the investigation of the impact of the current ripple on the battery parameters, the battery is subjected to both small and large current ripples.  The results of the tests prove that the current ripple doesn't have a detrimental effect on the battery parameters. However, the current ripple causes a voltage ripple which does interfere with the operation of the Battery Management System. As the voltage ripple causes the instantaneous cell voltage to exceed the voltage limits while the dc-value of the cell voltage is within limits, the maximal allowable battery voltage must be reduced. As a consequence, the useful energy content of the battery is reduced.

https://lirias.kuleuven.be/handle/123456789/353008

• Prof. dr. ir. Johan Driesen (promotor)
• Prof. dr. ir. Geert Deconinck (mede-promotor)
• Prof. dr. ir. Paul Sas (voorzitter/chairman)
• Prof. dr. ir. Ronnie Belmans (secretaris/secretary)
• Dr. Gerrit Jan Schaeffer , VITO nv
• Prof. dr. Luc Dupré , Universiteit Gent
• Prof. dr. Göran Lindbergh , KTH