2004款Prius的电池系统

Development of a New Battery Systemfor Hybrid VehiclesShuuichi NagataHiroya UmeyamaYoshiaki KikuchiHaruyoshi YamashitaElectric & Hybrid Vehicle Engineering Div.TOYOTA MOTOR CORPORATION1,Toyota-cho,Toyota,Aichi 471-8572Phone / FAX: +81-565-23-6346/5744AbstractToyota Motor Corporation has developed the next generation Prius, which reflects our continuous environmental effort. For the new Prius, we have developed a new Ni-MH battery that plays an important role in the Toyota Hybrid System. With this new battery, we have realized further downsizing, weight and cost reduction as well as improvement of its usability, foreseeing a full-scale popularization of hybrid vehicles in the future. By improving the electrode and cell-to-cell connection structure, the internal resistance was lowered, and a higher output power from the battery module was achieved. This allowed us to reduce the number of battery modules without any effect on output performance. The volume and weight of the battery pack was reduced by approximately 15% and 25% respectively. With the new Prius, the input/output current has increased due to the downsizing of the battery. This results in increasing of heat generation in the battery. In order to cope with this issue, both battery configuration and battery cooling structure have been redesigned. This allowed us to enhance the cooling performance and reduce the temperature variation between modules. Furthermore, we improved the accuracy of the SOC estimation by optimizing the battery control system, so that we can cope with the expansion of the SOC range caused by the downsizing of the battery.Keywords: Battery, Hybrid, Battery Pack, Ni-MH1.IntroductionToyota Motor Corporation started marketing Prius, the world’s first production hybrid vehicle in December 1997 to help save resources and prevent global warming. This vehicle was introduced to North America and Europe in 2000:[1]. A total of over 110,000 units have sold as of March 2003, making Toyota a leader in hybrid technology throughout the world.We have been able to provide the new Prius with the world’s highest level of environmental performance and driving pleasure, true to its concept. We have realized a compact and lightweight battery system with improved usability and performance. This paper outlines the improvements the new battery system has achieved.2.Development of Battery ModuleFig. 1 shows the battery module for the new Prius:[2]. Fig. 2 shows the transition of the specific power and the specific energy. The prismatic battery module configuration of the new Prius follows that of its predecessor for superior heat releasing performance and ease of installation. The internal resistanceFig 1: New Prismatic Battery Module Fig 2: Specific Power and Specific Energy of Battery Module has been reduced by 30% from the previous model. This was achieved by reducing reactive resistance through the improvement of the electrode material, and structural improvements to the cell-to-cell connection also reduced resistance of the parts. As a result, we have realized the world’s top level of the specific power by improving it by 35%, as compared to the previous model. Table. 1 shows the specifications of the battery module. For the ’97 model Prius, we adopted a cylindrical battery module with 6 cylindrical Ni-MH battery cells connected in series. For the ’01 model,we adopted rectangular cells, six of which were connected in series into an integrated prismatic battery module. In addition, to improve output, we reduced the internal resistance of the battery by improving the structure of cell-to-cell connection. The new type battery provides the best output by reducing the internal resistance without changing the battery frame and capacity.Table 1: Battery Module Specifications3. Battery Pack ConstructionThe aforementioned improvements have enabled the new battery pack to have the same output as the previous model, but with less modules. Since the supply voltage is reduced because of the lesser number of battery modules, it poses a problem of lowering of motor and generator efficiencies. However, to improve this, the new Prius has adopted the variable-voltage system. If the number of battery modules is reduced, raising the battery voltage to a high level of 500 VDC can efficiently drive the motor and generator. We have thereby succeeded in reducing the total number of battery modules from 38 to 28,while retaining the battery pack output performance.Fig. 3 shows the construction of the battery pack. The new battery pack has 28 modules laid in a single row. The modules are held together with the end plates on both sides and the upper and the lower restraint rods. We have reduced the overall battery pack volume by 15% and the weight by 25% with the reduced number of modules and the adoption of plastic end plates and so forth.New PrismaticPrismatic Cylindrical Voltage 7.2V7.2V 7.2V Capacity 6.5Ah 6.5Ah 6.5Ah Weight 1040g 1050g1090g Dimension285mm(L)19.6mm(W)114mm(H)275mm(L)19.6mm(W)106mm(H)35mm(_)384mm(L)Fig 3: Battery Pack Construction4.Battery System4.1Battery Pack StructureFig. 4 shows the structure of the battery pack. Similar to the previous model, the new Prius has the following high-voltage components built directly into the battery pack from the viewpoint of the electrical safety:· System Main Relay (SMR)Independently installed 3 relays make effective use of the dead spaces in the vehicle.· Service PlugA built-in fuse to the Service Plug improves maintainability. Fig. 5 shows System Main Relays and Service Plug circuit.· Current SensorThe method of battery SOC estimation has been revised to promote cost reduction.· Battery ECUThe Battery ECU calculates the SOC on the basis of the battery current, voltage, and temperature. It also monitors abnormality of the battery system. These signals are transmitted to the vehicle control system.We have accomplished a sharp reduction of the size, weight, and cost by revising the internal circuits.Fig 5: Battery System CircuitFig 4: Battery Pack Structure Service PlugBattery ECU Battery ModulesSystem Main RelaysResistorRestraint RodsEnd Plates Lower CaseBattery Modules4.2Battery ControlCompared with the previous Prius, the battery voltage has been reduced because of the lesser number of the battery modules. Consequently, because of the increased current to the same level of power charge and discharge, the fluctuation range of the SOC increases as shown in Fig. 6. In addition, the holding energy of battery pack has been reduced from 1.8 kWh to 1.3 kWh or 70% of the previous model.To cope with the shortage of necessary battery energy for running the vehicle, we have optimized the method of SOC estimation. This has enabled us to expand the range of SOC usage, and retain the same level of energy for actual use as the previous model.Fig 6: Battery Input/Output and SOC during urban driving5.Cooling PerformanceConditioned cabin air is circulated to cool the battery pack . Because of the reduced number of battery modules, the input/output current has increased compared to the previous model; even when charging and discharging the same power. Reducing the internal resistance of battery modules, which suppresses the heat generation to the level of the previous model, has solved this problem. Fig. 7 shows the flow of the cooling air, and Fig. 8 the transition of the battery temperature during urban driving. We have been able to reduce the temperature variation between the modules as compared to the previous generation. This has been accomplished by battery module reduction, the optimization of inlet/outlet ducts, and modification to the pack structure.Fig.7: Flow of the Battery Cooling Air[ ’01 Model ][ ’04 Model ]Rear SeatBlowerBattery PackOutlet DuctsInlet DuctsFig 8: Battery Temperature during urban driving6.Cycle LifeWe have promoted longer cycle life by improving the separator, and optimizing battery cell design.Fig. 9 shows the relationship between the charge/discharge pattern on actual vehicle converted into the running distance and the rise in the internal resistance. While the battery on the new Prius has improved output performance, it retains the cycle life equivalent to, or greater than, the previous model.Fig 9: Cycle Life Charactaristics7.Conclusion(1) We have been able to reduce the size and weight of the battery pack by improving the batterymodule, pack, and overall system.(2) We have improved the method of battery SOC estimation. This allows us to expand the usable rangeof SOC. This enables us to use the same level of energy as the previous model, even with the reduced number of battery modules.(3) The reduction of battery modules, and the optimized battery cooling construction have reduced thetemperature variation among the battery modules.(4) The improved separator, and the optimized battery cell design have realized the cycle life equivalentto, or greater than, the previous model.However, further technological development to reduce size, weight and cost of the battery pack is needed for the propagation of hybrid vehicles.[ ’01 Model ][ ’04 Model ]012345060012001800240030003600time [sect e m p e r a t u r e [??]-30-20-10010203040506070POWER [kW]12345060012001800240030003600time [sect e m p e r a t u r e [??]-30-20-10010203040506070POWER [kW]8.References[1]Tomokazu Yamauchi, Shogo Yoneda, Yoshiaki Kikuchi, Yoshimi Shoji. Development of a New Battery Systemfor Hybrid Vehicles, EVS17, 2000.[2]Masato Ohnishi, K oujiro Ito, Shin-ichi Yuasa, Noriyuki Fujioka, Takashi Asahina, Shinji Hamada, ToyohikoEto, Development of Prismatic Type Nickel/Metal-Hydride Battery for HEV, AABC, 2003.9.AuthorsShuuichi NagataAssistant ManagerElectric & Hybrid Vehicle Engineering Div.Power Train Development GroupToyota Motor CorporationTel: +81-565-23-5159 Fax: +81-565-23-5759 E-mail: nagata@shuuichi.tec.toyota.co.jpHiroya UmeyamaAssistant ManagerElectric & Hybrid Vehicle Engineering Div.Power Train Development GroupToyota Motor CorporationYoshiaki KikuchiAssistant ManagerElectric & Hybrid Vehicle Engineering Div.Power Train Development GroupToyota Motor CorporationHaruyoshi YamashitaAssistant ManagerElectric & Hybrid Vehicle Engineering Div.Power Train Development GroupToyota Motor Corporation。