Design and experiment of a low-temperature charging preheating system for power battery packs with an integrated dissipative balancing function

Abstract

The performance degradation of lithium-ion batteries (LiB) at low temperatures, as well as variability among batteries after battery grouping, limit the application range of electric vehicles (EVs). A low-temperature preheating method for power battery packs with an integrated dissipative balancing function is proposed in this research. The system builds its topology structure and sets the placement of heating units in the battery pack, as well as using heating units as preheating elements and balancing resistors. Furthermore, this paper presents an online balancing control technique to completely utilize the minimal capacity single battery module and formulates the balancing control threshold for different SOCnew states. The results showed that the temperature rise and temperature difference caused by the battery pack balancing process are within the range of 7 °C under the full operation conditions of balancing resistance at an ambient temperature of 20 °C. Under a −20 °C ambient temperature, the preheating system can raise the average temperature of the battery pack to 16 °C within 40 min and keep the temperature inside the battery pack above 0 °C for the following 4 h. This paper provides a new idea for coupling the research of efficient balancing technology and low-temperature preheating technology for power battery packs.