Improving the Performance Attributes of Plug-in Hybrid Electric Vehicles in Hot Climates through Key-Off Battery Cooling

Abstract

Ambient conditions can have a significant impact on the average and maximum temperature of the battery of electric and plug-in hybrid electric vehicles. Given the sensitivity of the ageing mechanisms of typical battery cells to temperature, a significant variability in battery lifetime has been reported with geographical location. In addition, high battery temperature and the associated cooling requirements can cause poor passenger thermal comfort, while extreme battery temperatures can negatively impact the power output of the battery, limiting the available electric traction torque. Avoiding such issues requires enabling battery cooling even when the vehicle is parked and not plugged in (key-off), but the associated extra energy requirements make applying key-off cooling a non-trivial decision. In this paper, a representative plug-in parallel hybrid electric vehicle model is used to simulate a typical 24-h duty cycle to quantify the impact of hot ambient conditions on three performance attributes of the vehicle: the battery lifetime, passenger thermal comfort and fuel economy. Key-off cooling is defined as an optimal control problem in view of the duty cycle of the vehicle. The problem is then solved using the dynamic programming method. Controlling key-off cooling through this method leads to significant improvements in the battery lifetime, while benefiting the fuel economy and thermal comfort attributes. To further improve the battery lifetime, partial charging of the battery is considered. An algorithm is developed that determines the optimum combination of key-off cooling and the level of battery charge. Simulation results confirm the benefits of the proposed method.

Analysis of Behavior in the Use of Plug-in Hybrid Electric Vehicle and Hybrid Electric Vehicle in the Tropics

“…The dynamic program method is used to solve the problem. And the research results showed significant benefits [11]. One crucial parameter that is considered by the buyers is the efficient use of fuel.…”

Reliability Assessment under High Penetration of EVs including V2G Strategy

“…The E HVAC v,t defined in ( 9) is the energy required to keep the vehicle and the battery within acceptable ranges. In addition to the energy required by the heater E HT v,t and the A/C E AC v,t , the battery pack may need cooling as its temperature can reach critical levels as high as 65 • C in hot climates [29,30]. These high temperatures reduce the battery life as well as increasing self-discharge [29][30][31].…”

An Optimal Domestic Electric Vehicle Charging Strategy for Reducing Network Transmission Loss While Taking Seasonal Factors into Consideration

“…This is because users prefer to switch on air conditioners in summer and heaters in winter to keep vehicle temperature within a comfortable range [19]. Therefore, average daily load curves of electric vehicles are different in different seasons.…”