Impact of smart charging on the EV battery ageing - Discussion from a 3 years real life experience

Smart charging is related to a possible adjustment of the charging sequences with some energetic constraints. It can be defined in different ways, namely depending on the specific objectives. However, they all result in similar consequences for the charging sequences, with regard to conventional charging: potential delay, interruption(s) and power modulation of the charging cycles. It is commonly admitted that smart charging will be necessary to face the growing deployment of EVs, namely for the local grid operators. Moreover, from the user point of view, smart charging can be seen as an additional motivation for the choice of an EV instead of a conventional car, if e.g. lower electricity tariffs are proposed for charging flexibility. In this paper, a quantitative evaluation is performed of EV battery ageing, in function of the charging conditions, with a special focus on the smart charging specificities. The study is based on real data from a three years continuous monitoring of five Peugeot iOn cars, a first of a kind campaign that was performed in Belgium in the Brussels area during the period 2011-2014. Different use profiles and charging patterns were observed. Among other elements, battery capacity and battery efficiency and their evolution in time were calculated, taking into account various factors, such as the seasonal impacts. It will first be highlighted that, whatever their charging patterns, all the considered cars are showing a significant flexibility potential, making them good candidates for smart charging. The impact of smart charging on battery ageing will then be discussed, with a focus on the charging frequency, the average state of charge and the impact of faster versus slower charge on battery capacity. This long time monitoring period allows to clearly identify the time evolution trends, leading to unique conclusions from the real life.