CR2032 button cell.Electric vehicle charging technology

　　The emergence of long-life and fast-charging batteries has also brought new options to the design of electronic devices. For example, design engineers can choose a small-capacity battery and solve the problem of insufficient capacity by charging frequently. As long as the battery life is long enough, there is no need to replace the battery during the service life of the device.

　　Combining the above-mentioned batteries with contactless charging technology enables the development of new devices that can be charged anytime and anywhere. The emergence of such devices will also lead to the improvement of contactless charging infrastructure. The joint development of corresponding equipment and charging infrastructure will form a new market and generate amazing profits (see Figure 1). In fact, the research and development of long-life and fast-charging batteries and non-contact charging technology has been quite active. In various industries, charging infrastructure developed using such technologies has

　　Electric vehicles are a touchstone for new technology

　　Development of lithium-ion batteries for electric vehicles has resulted in batteries that have a long life and can be charged quickly. Since their debut in 2004, this type of battery has been widely used in power tools and industrial equipment. By 2009, it may be officially used in hybrid and electric vehicles.

　　Automobile manufacturers will formally invest in the research and development of electric vehicles in the next one to two years. In order to significantly reduce the carbon dioxide emissions of automobiles, Masanori Ueda, a senior expert in the Technology Planning Department of Nissan Motor Planning/Advanced Technology Development Headquarters, believes: "It is imperative to develop electric vehicles that do not emit gas at all." Many other automobile manufacturers have also hold the same view.

　　For example, Mitsubishi Motors will start selling electric vehicles iMiEV in July 2009. The company plans to produce 2,000 vehicles in the first year after launch, 4,000 vehicles in the second year, and then gradually expand to an annual production of 20,000 vehicles. Nissan also plans to sell electric vehicles in Japan and the United States in 2010 and in China in 2011. By 2012, it plans to promote them to countries around the world. Even Toyota, which has been less active in electric vehicle research and development (the company is a leader in the hybrid car market), has said it will enter the electric vehicle market in 2012.

　　To expand the market for electric vehicles, it is necessary to increase the construction of infrastructure such as charging stations. The energy density of currently developed lithium-ion batteries for electric vehicles is only about 100Wh/kg, less than half that of the lithium-ion batteries used in laptops and mobile phones. This is mainly because batteries used in electric vehicles pay more attention to safety and service life than portable devices. Currently, limited by the cost and size of rechargeable batteries, the driving distance of electric vehicles per charge is only 100km to 200km at most, which is only about 1/4 of that of engine-powered vehicles.

　　The improvement of charging infrastructure is an important prerequisite for the popularity of electric vehicles. In fact, companies and local governments are working together to improve charging infrastructure in various countries around the world, the most prominent of which is the American company Betterplace. The company is joining hands with the governments of Israel, Denmark and other countries to actively prepare to build charging infrastructure for electric vehicles. In Israel alone, it plans to build 500,000 charging stations.

　　If the charging infrastructure can be further improved, the driving distance of electric vehicles after each charge will no longer be a problem for users. By then, users will be more concerned about the charging time and charging method of the battery, which will lead to a change in thinking during the battery development process. The past practice of desperately increasing battery energy density in order to extend battery life is no longer advisable. For developers, it is more important to reduce battery costs and clarify corresponding product positioning.

　　Resonant non-contact charging technology is worth looking forward to

　　Once users recognize the use of repeatedly charging batteries in a shorter period of time, there will be more and more demand for non-contact charging (see Figure 3). Automatic handling equipment usually starts and stops repeatedly at a fixed frequency. Therefore, the industry is developing equipment that does not require manual charging and uses non-contact charging technology to charge. In terms of electric vehicles, such as buses that run regularly, experiments with non-contact charging systems have also begun.

　　Figure 3 The goal is to charge on the move

　　At present, practical non-contact charging systems mainly use electromagnetic induction, that is, one coil supplies power to another coil. However, the electromagnetic induction non-contact charging system has the following three problems: first, when the position is shifted, the charging efficiency will decrease; second, when foreign objects enter, local heating will occur; finally, electromagnetic waves reach high Frequency protection is also not easy to solve. Therefore, the development of electric field or magnetic field resonance non-contact charging systems has become more active in the near future. For example, the electric field resonance non-contact charging system being developed by Takenaka Public Works Shop in Japan can solve the problems of local heating, electromagnetic wave and high-frequency protection in electromagnetic induction systems.

　　In addition, the Massachusetts Institute of Technology (MIT) announced its research on magnetic resonance non-contact charging technology in June 2007. If this technology goes well, it will be possible to carry out all-round power transmission in space. Using this technology, electric vehicles will be able to charge through roads or guardrails while driving.

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