The development of electric buses is facing the challenge of battery technology, and the bottlenecks faced by battery technology are mainly focused on the length of charging time and the length of cruising range. The charging time will directly affect the daily operation of the electric bus. If the rapid charging technology can be applied, the electric bus will not only be able to get rid of the era of overhead trolley trams, but will also relatively weaken the short battery life for the normal use of electric buses. influences. Therefore, foreign scientific research institutions and passenger car companies have started research on fast charging technology. The reporter consults relevant foreign newspapers and papers to understand the progress of foreign research and application of rapid charging technology.
Lithium titanate battery rapid charging technology matures
A report released last year by the University of California Davis Institute of Transportation presented an experiment on the rapid charge technology of lithium titanate batteries. According to this report, lithium titanate battery technology has been widely discussed in the academic community as a way to effectively extend the range of electric vehicles and reduce charging time.
According to reports, this experiment uses three lithium-ion batteries. The main purpose is to observe what changes occur in the characteristics of the lithium ion chemical composition when the charging rate is greatly increased. The experimental results show that lithium titanate compounds have greater advantages than other chemical substances (especially nickel, cobalt, manganese chemical substances) in adapting to rapid charging.
This paper published the results of a large-scale fast-charging experiment of 50-amp-hour low-temperature oxide batteries and 24-volt battery packs from Altai Technologies, USA. In the experiment, the battery pack was mounted on a special mechanical device so that the voltage of a single battery and the change of the internal temperature could be monitored at all times. The cooling of the battery pack was realized by a cooling plate installed at one end of the battery pack. The entire life cycle of the 24 volt battery pack is still in progress.
The entire experimental process includes two processes: high-rate charging and low-rate discharge. The charging process lasts 10 minutes. The discharging process lasts 80 minutes. The charging process is performed in a 200 amp unit current environment. The discharging process is operated in a 25 amp unit current environment. 10 The voltage after minute charging corresponds to the voltage at which the battery pack storage capacity is 90%. The voltage after 80 minutes discharge corresponds to the voltage when the battery pack storage capacity is 24%, and the power consumption of the battery pack during the entire discharging process is 33.3 ampere hours.
The entire experiment cycle was completely modeled on the fast charging environment during the actual operation of the electric bus. After 285 cycles of experiments, the battery did not show any obvious signs of degradation in the ampere-hour capacity and voltage response. The fixed battery pack had no When the fan is cooled, the maximum internal temperature of the battery pack is 40 degrees Celsius.
This paper shows that although the entire life cycle experiment for lithium titanate batteries is still in progress, the experimental results of the 285 charge and discharge cycles of the battery prove that the lithium titanate battery fast charge technology has a great influence on the storage capacity, voltage, and temperature. Without obvious defects, the theoretical research on the rapid charge technology of lithium titanate batteries has matured.
ABB Group 15 seconds fast charge
According to reports, the new high-capacity fast charging technology developed by ABB, a Swiss power and automation company, allows electric buses to bid farewell to overhead overhead transmission lines. Electric buses will enter a new era of rapid charging technology.
“With this new fast charging technology, we can try to use a new generation of electric buses to serve urban public transportation, and such electric buses will not need to rely on overhead transmission lines.†ABB Group Acting Chief Technology Officer Les said at a press conference. According to him, this rapid charging technology will pave the way for the construction of more flexible and cheap public transportation facilities, and at the same time, it will reduce the pollution caused by the operation of public transport facilities and reduce the noise caused by public transport facilities.
This new charging technology will be used in fast charging stations along the bus lines, and the electricity supply comes from the public grid. The fast charging system of the electric bus is charged through a laser-controlled moving arm connected to a quick charging station, eliminating the need to rely on conventional overhead wires and tram-trailers for power. With this new fast charging technology, charging takes only 15 seconds to ensure that the bus runs on time.
It is reported that the new technology will be used on a large batch of electric buses that can carry up to 135 passengers. The electric buses are scheduled to operate between the Geneva airport and the Geneva International Exhibition Center. . This fast charging technology is used as follows. First, the electric bus carries a fully charged battery starting from the starting station. Every three to four stations will set up a quick charging station. The fast charging device at the top of the vehicle can pass a The laser-controlled moving arm self-adjusts its height to connect it to the outlet of the quick-charging station. After the fast charging system is connected to the charging station, the charging station can transmit electric power of 400 kilowatts for 15 seconds to the electric bus, and the 15 seconds quick charging process completely occurs between when the vehicle gets on and off when the vehicle stops. Therefore, this rapid charging technology will not have any impact on the normal operation of electric buses. When the electric bus enters the terminal station, it takes 3 to 4 minutes to fully charge the battery.
According to relevant person in charge of ABB Group, this high-power electric bus rapid charging technology was developed to meet the heavy traffic schedules in urban areas. In these areas, concerns about overhead wires have affected the development of electric buses. For example, in many historical and cultural cities, elevated wires have caused much controversy. The controversy has mainly focused on whether elevated wires will affect the aesthetics of the city. In some areas, overhead wires need to be erected on residential buildings. The operation of trolley buses will give people living here. The daily lives of residents have caused great difficulties. However, with the application of ABB Group's high-power and fast charging technology, these problems will be solved. This new technology will also drive the further development of electric buses.
Volvo’s new bus enables fast charging
Not long ago, Volvo's new 7900 plug-in hybrid bus was successfully recharged for the first time at a charging station in central Gothenburg. It is Goteborg Energy that charges the new plug-in hybrid bus. The bus will be operated on the 60 bus line. Goteborg Energy will set up fast charging stations on both ends of the 60 bus line. The single quick charging station can also provide 3 Volvo 7900 plug-in hybrid buses. The car is charged. It takes only 5 to 8 minutes to charge the bicycle. The relevant person in charge of Gothenburg Energy Company stated: “The electricity provided for this plug-in hybrid bus comes from the wind turbine near the charging station. Compared with traditional fossil fuels, the new renewable energy channel is to build a sustainable public The traffic mode provides an exciting model, in which urban public transportation will truly achieve zero emissions. It is reported that the energy generated by 10 turns of a high-power wind turbine can satisfy a 7900 plug-in type The energy required for a one-way line of a hybrid bus.
The 7900 plug-in hybrid bus was developed based on the technology of the 7900 hybrid bus. Compared to the 7900 hybrid bus, the new 7900 plug-in hybrid bus has added a large-capacity energy-optimized battery. And fast charging performance. The traditional Volvo hybrid bus shuts down the diesel engine when it stops at the station. After a few seconds of operation when exiting the station, the diesel engine will restart. During the running of the bus, it will depend on the diesel engine for most of the time. The electric mode only functions as energy recovery during braking and energy boosting at startup. The new 7900 plug-in hybrid bus, due to the installation of a large-capacity energy-optimized battery, can rely on the electric mode to complete most of the journey, and truly achieve zero emissions and quiet operation in the electric mode. Rapid charging technology provides effective guarantee for the punctual operation of buses.
The development and application of foreign fast charging technology is a good incentive and supervision for the domestic electric bus industry. How to seize the good opportunity for the development of electric buses and make them bigger and stronger in scale and technology is a question that should be considered by the electric bus industry in China.
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