Consideration of battery degradation and charging infrastructure through long-term use experience of an electric vehicle

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1 EVS28 KINTEX, Korea, May 3-6, 2015 Consideration of battery degradation and charging infrastructure through long-term use experience of an electric vehicle Yoshinori Kondo 1, Junichi Yasu 2 and Yoshihiko Karakama 3 1 (corresponding author) National Institute for Environmental Studies, 16-2, Onogawa, Tsukuba, Ibaraki , Japan, kondos@nies.go.jp 2 Ranet co., Japan, 3 Association of the promotion of electric vehicles, Japan, Abstract The performance degradation of the battery installed in the electric vehicle (EV) and the information in the change of the situation regarding charging places in a public were studied. This research is based on the record of the EV used for commuting in the distance of about 50 km of one way, every weekday, for nearly three years. The mileage amounted to around 80,000 km. During this test period, the battery was charged twice in a morning and a night for around 1,200 times. To examine the performance degradation of the battery, we chose the night run data when auxiliary device, such as an air-conditioner or a heater was not activated. The reasons were to avoid 1) the effect of auxiliary devices, 2) the influence of road traffic situations, such as congestion, and 3) the variation in running qualities, such as acceleration, deceleration, constant speed running, and stopping. We examined the deterioration of the battery performance in this test period by comparing the change of the electricity consumption rate. As a result, we confirmed that there was almost no performance degradation even after approximately 1,200 times charge-and-discharge cycles, in the investigated EV battery. We also found that queues waiting for the turn of charging often appear in the public charging places as a certain number of EVs and plug-in hybrid vehicles (PHEVs) now spreading through the market. We confirmed the reason why PHEV drivers also prefer to use the quick charger at the public charging place, although basically they do not need to worry about running out of battery but it requires a longer time to charge by the normal charger at home. Consequently, this suggests the necessity to promote the installation of quick chargers according to the spread of not only EVs but also even PHEVs. Keywords: long-term actual use data, battery degradation, competition at charging spot, battery electric and plugin hybrid vehicles 1 Introduction We collected the long-term actual use data of a commercially available electric vehicle (EV). The reason is to find a solution whether or not a battery for EV has the durability with more than of life of EV. By the method that we simulate the real use in the product manufacturer or were decided in standards such as the ISO, we will carry out the performance evaluation of the product. However, EVS28 International Electric Vehicle Symposium and Exhibition 1

2 they are simulation to the last, and there is not it in the reality. We clarified that we could stretch out the distance of the vehicle available several percent in mean speed and relations of the electricity consumption rate (ECR), influence on ECR by the use of the auxiliary device, controlling the cruising speed in the expressway again using actual use data of EV for approximately one and a half years in previous report [1]. In this paper, it is intended that we confirm longterm actual use data of EV that were piled up the use results of one and a half years more whether the deterioration of the battery is up for the cause. Furthermore, in Japan, plug-in hybrid vehicles (PHEVs) that can run more than 20km as EVs are gradually spreading. When there is little registration number, it is available public charge facilities, but PHEV and EV which need longtime charge at home concentrate on public charging facilities, and it is possible for a queue, and is supposed monopolistically by the characteristic that we can charge free that doing where a user might feel stress (Upset) in this situation. So, we summarized opinions from one user about this charging situation, and we report about relations of battery charger and the vehicle number as our personal opinion. The main purpose of the vehicle use on weekday is commuting to workplace and return to domicile. In addition, weather condition and air temperature data when using a vehicle are collected from the internet site of the Meteorological Agency to grasp the use situation of the auxiliary devices such as an air-conditioner or the heater which greatly influenced an electricity consumption rate equivalent to the mileage of the engine vehicle and relations of the outside temperature and made the database which gathered up the use situation and outside temperature of EV. 2.3 Charging spot For the charge, one travel distance was more than half of one charge mileage [catalogue level] of the vehicle, therefore, the frequency of charge was 2 times in the morning and night time. We used public charging stations where is within the range of 1km of a volunteer s house at night time charge. In the morning he charged the EV by AC200V single-phase alternating current at NIES. The ability for charge of the battery charger of the public utility gathered up information in Table 3 that was 20kW (medium speed battery charger) or 50kW (quick-charger). 2 Research Method 2.1 Test vehicle The test vehicle used for an investigation is electric vehicle imiev-m of the 2012 model year made by Mitsubishi Motors Corporation (Table 1). The volunteer lives in Tokyo and works at incorporated administrative agency National Institute for Environmental Studies (NIES) in Tsukuba, Ibaraki Japan where are 60km away from central Tokyo. He used the car to go to the NIES every day on weekdays. 2.2 Collection and arrangement of data Data and the details of the collection method about the use of EV are recorded the time and odometer at starting and finishing the trip, the use of auxiliary devices (air-conditioner, heater, headlight, windshield wiper), the road used which is public road or expressway (Table 2). 2.4 Data analysis We found ECR by quantity of charge and the travel mileage from the last charge. We arranged ECR based on road classification, the use situation of the auxiliary device at night. By use time and the mileage, we calculated mean vehicle speed and examined the relations between mean vehicle speed and ECR. In addition, the road congestion situation greatly fluctuated by attendance rushes in the morning and excluded it in the examination of the battery deterioration because the influence of the traffic condition like congestion on the ECR was big. 2.5 Use situation of charging spots While Nissan sold more than 200,000 EVs in the world, the Japanese domestic registration number of EV LEAF became approximately 50,000 vehicles at the end of 2014 [2]. In addition, sale of PHEV where there was EV run was brisk during 20-30km, and approximately 20,000 vehicles were registered in Because is maintained approximately 3,000 places the quick-charger corresponding to the CHAdeMO EVS28 International Electric Vehicle Symposium and Exhibition 2

3 standard that Japan suggested in the all over Japan [3], in late years some EV is used in society in Japan; is in a situation, and it is thought that the use environment of EV improved. A lost thing was guessed in the situation available freely than before by vehicle number using these facilities having increased about charge in the public utility because there were many cases of the present conditions free of charge. Therefore we carried out hearing about the situation at the time of the charge of the interval where the use reached to the subject who had you take the use record for approximately three years to date from the first and arranged influence of the increase of charge facilities and the increase of the use number. 3 Results and Discussions 3.1 Summary of the EV use The vehicle started the use from March 12, 2012 and, as of January 15, 2015, is total mileage 79,686km, charge frequency of 1,179 times. We showed the monthly use number of times and the monthly mileage in figure 1. Use frequency and the mileage decreased in the latter half of 2013, but were approximately 40 times of trips, use situation of approximately 2,000km monthly when they looked at the whole investigation period. In addition, we showed ECR in the use at the time of the attendance and a change of the outside temperature in figure 2. ECR fluctuated from 120Wh/km to 180Wh/km, but was 150Wh/km on the average. We showed ECR at the time of the night return and the situation of the outside temperature in figure 3. For the ECR calculation with the AC base, we cannot compare it simply in the morning to become DC-based ECR at night, but the use understands that ECR is approximately uniformity (120 ± 20Wh/km) to date from the first. 3.2 Secular variation of electricity consumption rate (ECR) We extracted the data of the ECR using an expressway without using an air-conditioner and a heater and checked relations with the charge number of times. Because the ECR changed if mean vehicle speed was greatly different, we demanded fate, the mean and dispersion between data wards every seasons such as in spring or autumn (Table 4) If we begin to use EV where it is thought that we was used to driving of EV enough and am based on Period2 one year later, Period4 approximately one year later showed a low value to ECR several percent, but you may consider it to be about the same if we recall that the minimum unit of the movement distance is 1km, and it may be said that the performance of the battery is maintained. Furthermore, Period5 one year later shows ECR having a small several percent in comparison with Period3, but will be an error range for a similar reason. As a result of these examination, the performance of initial (Period1) knew that we maintained performance approximately at the same level in Period5 which was approximately 1,000 times of after charge and discharge approximately two years later. Because the number of charge and discharge where the performance of the battery maintains initial performance in order of a cell, a module, a group battery decreases, it is very important that this vehicle deployment battery maintaining performance more than original 80% showed all these performance to even 10,000 times of after charge and discharge in the real use situation at a cell level. 3.3 Use situation of charging facilities We compiled the answer of the subject and arranged the difference (Table 5). It was available approximately monopolistically until March 2013 that was around three ridership, but, by increase in EV and PHEV, other vehicles charged twice once on the average and knew that waiting for charge occurred afterwards. PHEV only becomes the HEV that burns fossil fuel if a battery residual quantity disappears, and an electric lack does not have it, but it is with long time, and the electricity fee for use is necessary for the charge at home. On the other hand, PHEV owner was high in frequency and knew what we used because the quick-charger of the public utility was around 30 minutes in free of charge and a charge time, and convenience was high. In addition, it is thought that a vehicle concentrated on CS1 when a lot of cases after 21:00 are over that time at the charge facilities use time of the subject because the facilities installing CS2 are not available. EVS28 International Electric Vehicle Symposium and Exhibition 3

4 Available time is limited to the battery charger maintained by vehicle dealers in the neighborhood within the business hours of the shop, and the vehicle concentration to CS1 occurs by the circumstances like the use limit of CS2. The battery charger setting number of the CHAdeMO standard, the number of the charge stations were approximately 3,000, but, at the end of 2014, it became clear that big inconvenience occurred by a limit of the use time. If vehicles using electric runs such as EV or PHEV mainly will increase in future and aim at the spread, the abolition of extension or the limit is necessary between available time of the quickcharger. In addition, there is two correspondence when we build the charge station in another place that installs an additional battery charger in the charge station when the users of charge facilities increase. When a user is less than 15 according to references [4] on a day, social cost turns out low, but one building the charge station will be necessary for the examination about the time available separately social, to make it widely available. The service such that vehicle manufacturer informs in consideration of a battery residual quantity, the geographical situation of the charge infrastructure to the charging spot is realized to raise the convenience of the user, but most of the charging spot of this case are battery chargers of the dealer setting and are not usable outside the business hours. The abolition of the limit of the use time is necessary to give real convenience. In addition, it was thought that one battery charger could serve only around five EV if the state that had few waiting time of the charge was desirable for a user. number and the increase of the public charging spot, we interviewed one user. As a result, 1) charging spot was one place, and there was not use number for the waiting for charge at the time of around five, but it was suggested that measures such as doing it for 24 hours to lengthen the business hours of the charging spot with the use limit that a vehicle drifted to the open for 24 hours charging spot because the state that was not available existed and to be awaiting charge and raised 3) real convenience that accelerated it if available were necessary for the limit for business hours even if 2) public utility and charge facilities of the dealer where waiting for charge occurred as for one of two times when ten or more came to always use it increased. 5 References [1] Y. Kondo, et al., To What Extent Can Speed Management Alleviate the Range Anxiety of EV?, Proceedings of EVS27, [2] ( accessed) [3] ( accessed) [4] Takuya Oda, Muhammad A., Takashi M., and Takao K., Cost Benefit of Quick Charger for Electric Vehicle Considering Station Access and Charger Extension, Proceedings of the 31 st Conference on Energy, Economy, and Environment, 104p, , Tokyo, Japan (Abstract in English). Acknowledgments Authors wish to thank Mr. Hidenori Konno for his great support to collect long-term actual use data of an EV. 4 Conclusion As a result of almost extracting the run data of the condition for the cause with the use actual situation of approximately three years of the commercial electric vehicle, and having examined the deterioration of the deployment battery, it was thought that even approximately 80,000km, approximately 1,200 times of after charge and discharge had little deterioration. In addition, about the charge turn of events of the EV user with increase in spread of EV/PHEV EVS28 International Electric Vehicle Symposium and Exhibition 4

5 Authors Table 2 Items recorded or measured and sources Yoshinori Kondo is a Senior Researcher at National Institute for Environmental Studies, Japan (NIES). He received the B., M., and Dr., engineering degrees from Kobe University. He joined NIES in His principal research areas are instrumental engineering and environmental systems engineering, His current interests are electric or human-powered mobility, public transportation, and human health issues accompanying vehicle emissions. Table 3 Battery chargers in the public charging spot Junichi Yasu is a Director of Advanced Technology Group at K.K. Ranet. He received the B. engineering degree from Meisei University. He is supporting NIES as a Visiting Researcher from His interest is low-carbon mobility. His another job responsibility is a Technical Manager of Dieseltec Japan at Hidria Corporation (Slovenia). Yoshihiko Karakama, MA of Ec., is a Senior Researcher at the Association for the Promotion of Electric Vehicles, Japan (APEV). He received the B. economics degree from Waseda University, and M. economics degree from Saitama University. He joined APEV in His interest is business model construction and market research for the diffusion of EVs. Figure 1 The number of trips at each month and the monthly mileage from test starting Table 1 Vehicle specification Figure 2 ECR and Outside Temperature EVS28 International Electric Vehicle Symposium and Exhibition 5

6 Figure 3 ECR(Left-axis) and outside air temperature(right-axis) at return to domicile Table 4 DC-based ECR in return [night run] using a expressway and mean vehicle speed Table 5 The situation of the charging spot of one day EVS28 International Electric Vehicle Symposium and Exhibition 6