Summary of the latest charging technologies of world-renowned electric vehicle manufacturers

Introduction: With the global shortage of oil resources and the vigorous development of new energy, more and more automobile manufacturers and even some Internet companies (such as Google) have begun to develop electric vehicles, and electric vehicles have gradually entered our lives. Although electric vehicles are not very popular in China at present, people in developed countries such as Europe, the United States and Japan have gradually begun to accept electric vehicles. How much do you know about electric vehicles? In fact, the biggest difference between electric vehicles and ordinary cars is the difference in driving energy, one is electricity and the other is chemical energy. Let's take a look at the latest charging technology and applications of well-known global electric vehicle manufacturers from the perspective of charging technology.

As early as last year, Google launched a wireless charging station for electric vehicles, which was used on a Nissan Leaf pure electric vehicle, see the picture below.

This sci-fi, button-like device does away with the charging piles, power sockets and even wires required for charging ordinary electric vehicles. Instead, it uses a power supply and transformer hidden underground. Electric vehicles equipped with special devices only need to approach the charging area to charge their batteries through the inductive charging device.

I believe everyone must be curious about the charging technology of electric vehicles. Now, the editor of Electronics Enthusiasts Network will introduce to you the latest charging technology of electric vehicles around the world.

1. Analysis of contactless electric vehicle charging methods

Contactless charging is also called wireless charging.

At present, there are three types of contactless charging devices: electromagnetic induction, magnetic resonance, and microwave. Let's take a closer look at the working principles of these three methods and some of the problems that still exist.

1. Electromagnetic induction method

Electromagnetic induction is the most practical charging method that transmits power between the power transmission coil and the receiving coil. When an alternating current flows through the power transmission coil, an alternating magnetic flux is generated between the transmitting (primary) and receiving (secondary) coils, thereby generating an induced electromotive force in the secondary coil that changes with the magnetic flux, and outputs an alternating current through the receiving coil terminals.

The current problems are: the power transmission distance is relatively short (about 100mm), and when there is a large deviation between the power transmission and receiving parts, the power transmission efficiency will drop significantly; the power size is directly related to the coil size. When high-power transmission is required, more investment must be made in infrastructure construction and power equipment.

2. Magnetic resonance method

The magnetic resonance transmission method was successfully developed by the Massachusetts Institute of Technology (MIT) in 2007. Since it was made public, it has attracted widespread attention from countries around the world.

It is mainly composed of power supply, power output, power receiving, rectifier and other main parts. The principle is basically the same as electromagnetic induction. When current passes through the power transmission part, the alternating magnetic flux generated causes the receiving part to generate an electric potential, outputting current when charging the battery.

The difference from the electromagnetic induction charging method is that the magnetic resonance method adds a high-frequency driving power supply and adopts an LC resonance circuit that combines a coil and a capacitor, rather than a simple coil that constitutes the power transmission and reception units.

The value of the resonant frequency changes with the distance between the power transmission and receiving units. When the transmission distance changes, the transmission efficiency will also decrease rapidly, just like electromagnetic induction. For this reason, the resonant frequency can be adjusted by the control circuit so that the circuits of the two units resonate, that is, "resonance". Therefore, this magnetic resonance state is also called "magnetic resonance".

By changing the transmission and reception frequencies under the control of the control loop, the power transmission distance can be increased to about several meters, while the resistance of the two unit circuits is reduced to a minimum to improve the transmission efficiency.

Of course, the transmission efficiency is also related to the diameter of the sending and receiving electrical units. The larger the transmission area, the higher the transmission efficiency. The current transmission distance can reach about 400mm, and the transmission efficiency can reach 95%.

3. Microwave method

The power is transmitted using a 2.45GHz radio wave generator, which is basically the same as the "magnetron" used in microwave ovens. The transmitted microwaves are also AC waves, which can be received by antennas in different directions and converted into DC power by a rectifier circuit to charge the car battery.

To prevent microwaves from leaking out during charging, the charging part is equipped with a metal shielding device. During use, the effective shielding between the power transmission and reception can prevent microwaves from leaking out.

The main problem at present is that the efficiency of magnetron in generating microwaves is too low, causing a lot of electricity to be converted into heat energy and wasted.

2. Uncovering the secrets of electronic design in the Chevrolet Volt electric car

Engineers work as a challenge and learning experience, sometimes it can be pure fun. That was the starting point for John Scott-Thomas, product marketing manager at UBM TechInsights, and Al Steier, senior manager and design prophet at Munro & Associates, to tear down the hybrid Chevy Volt this past January to see what was causing the whirring and buzzing sounds, while also understanding how the car's craftsmanship was put together.

Here are some of the insights they gained from creatively dismantling VOLT over three days.

The source of energy: batteries

The VOLT's lithium battery is composed of four modules arranged in a T shape, so that it can be properly placed under the rear seat and in the middle slot of the front seat. The busbar connects the four modules, and there is also an emergency power switch line to ensure the safety of the battery pack.

3. Wireless charging pads solve the problem of electric vehicle charging

According to the Detroit News, one of the reasons why electric and plug-in hybrid vehicles cannot be popularized quickly is that the charging process is complicated and cumbersome, and the supporting infrastructure construction cannot keep up. Take the Chevrolet Volt and Nissan Leaf as examples. Drivers must plug in the power supply to charge their cars, which is indeed a bit inconvenient for large cars.

Many companies are working on new ways to break free from the constraints of plug-in charging and charge vehicles with wireless charging pads fixed to the ground. Coils installed on the bottom of the car connect to the charger when the car is parked on the wireless charging pad. The wireless charging pad is plugged in to charge, and the car does not need to be plugged in. Automakers and suppliers expect to sell wireless charging pads around 2015.

Phil Gott, an analyst specializing in powertrain research and development at IHS Automotive, said that according to feedback from some Chevrolet Volt and Nissan Leaf owners, many people complained that electric vehicle charging cables are difficult to clean and easily tangled. The development of wireless chargers can save consumers from these troubles.

It is reported that there are only two ways to achieve "wireless" charging. One is electromagnetic induction, similar to the principle of electric toothbrushes returning to their original positions; the other is to use magnetic resonance.

4. A Japanese research team's results: How to charge electric vehicles while they are moving

With the beginning of the fuel revolution, we will gradually reduce our dependence on gasoline and gradually turn to rechargeable battery technology. Therefore, electric vehicles have gradually begun to develop, but there is a key problem at present - how to charge electric vehicles while driving?

The head of the research team, Takashi Ohir, is in the middle of the picture. This is a group photo of the research team members

The research team conducted tests on ordinary roads in Japan and showed that electricity can be transmitted through a 6-inch thick road surface.

Some countries and regions have built many electronic gas stations along the road, but now a Japanese research team has come up with a new solution and successfully demonstrated how to charge a moving car through 12 inches of concrete.

In a test, a research team from Toyohashi University of Science and Technology in Japan used special tires to charge a moving car on an asphalt road. The research team said that "electric vehicles on electrified roads" have not yet encountered technical obstacles in road driving.

The concrete thickness in the test could be scaled up to 12 inches, although that would require increasing the voltage 100 times to power a car. He noted that this did not present any technical problems.

Takashi Ohir stressed that the efficiency of power transmission through concrete is 80-90%, or even higher. Currently, there are other companies looking to develop similar technologies, such as Toyota, which plans to add a metal plate system to the road.

5. Flywheel battery energy storage technology for electric vehicles

The flywheel battery is a new concept battery proposed in the 1990s. When the flywheel rotates at a certain angular velocity, there is a motor in the flywheel battery. When charging, the motor operates as an electric motor. Driven by an external power source, the motor drives the flywheel to rotate at high speed, that is, using electricity to "charge" the flywheel battery, increasing the speed of the flywheel and thus increasing its function; when discharging, the motor operates as a generator, outputting electrical energy to the outside driven by the flywheel, completing the conversion of mechanical energy (kinetic energy) to electrical energy.

The energy storage element "flywheel" has been used by people for thousands of years, from the ancient spinning wheel to the steam engine during the Industrial Revolution. In the past, its inertia was mainly used to balance the speed and pass the "dead point". Because their working cycle is very short, each rotation takes less than one second. In such a short time, the energy consumption of the flywheel can be ignored. Now we want to use the flywheel to balance the energy of a cycle of up to 12 to 24 hours, and the energy consumption of the flywheel itself becomes very prominent. Energy consumption mainly comes from bearing friction and air resistance. People have reduced bearing friction by changing the bearing structure, such as changing the sliding bearing to a rolling bearing, a liquid hydrodynamic bearing, a gas hydrodynamic bearing, etc., and reducing air resistance by vacuuming. The bearing friction coefficient has been reduced to 10-3. Even so small, 25% of the energy stored in the flywheel is still lost within a day, which still cannot meet the requirements of efficient energy storage. Another problem is that conventional flywheels are made of steel (or cast iron) and have limited energy storage. For example, to make a power plant with a generating capacity of 1 million kilowatts generate electricity evenly, the energy storage wheel needs 1.5 million tons of steel! In addition, to complete the conversion of electrical energy into mechanical energy, a complex power electronic device is also required. Therefore, the flywheel energy storage method has not been widely used.

In recent years, the breakthrough progress of flywheel energy storage technology is based on the rapid development of the following three technologies: first, the emergence of high-energy permanent magnet and high-temperature superconducting technology; second, the advent of high-strength fiber composite materials; and third, the rapid development of power electronics technology. In order to further reduce bearing loss, people once dreamed of removing the bearings and suspending the rotor with magnets, but the test results failed again and again. Later, a British scholar theoretically explained that it is impossible for an object to be fully suspended by a permanent magnet (Earnshaw theorem), which made the experimenters quite discouraged. Unexpectedly, the dream of fully suspended objects has been realized in superconducting technology, which is really like nature's comfort to explorers.

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Let's take a look at the structure inside.

Flywheel battery schematic diagram Flywheel energy storage technology is an emerging energy storage technology. Like superconducting energy storage technology and fuel cell technology, it is an energy storage technology that has emerged in recent years and has great development prospects. Although chemical battery energy storage technology has been developed very maturely, it has problems such as limited charging and discharging times, serious environmental pollution, and high operating temperature requirements. This has made emerging energy storage technologies more and more valued by people. In particular, flywheel energy storage technology has begun to be more and more widely used in many industries at home and abroad.

6. Fast charging of electric vehicle batteries without damage

Facing the pollution caused by exhaust emissions from traditional fuel vehicles and the environmental and energy problems caused by excessive consumption of oil resources, electric vehicles have become the trend and hot spot of international automobile development with their good environmental protection and energy-saving characteristics. At present, governments of many developed countries in the world, famous automobile manufacturers and related industry research institutions are committed to the research, development and application promotion of electric vehicle technology.

The on-board electric vehicle charger is an indispensable component after the large-scale commercialization of electric vehicles. How to achieve fast and non-damaging charging of batteries by on-board chargers is one of the key technologies that must be solved before electric vehicles are put on the market. The charger designed in this paper is an on-board charging device installed on electric vehicles. By analyzing the current development status and development prospects of on-board batteries, the widely used valve-regulated sealed lead-acid batteries are used as the research object. The technology adopts the more advanced and mature inverter technology, which has the characteristics of small size, light weight, high efficiency, and large adjustment range. At the same time, from a functional point of view, it is also suitable for nickel-cadmium, nickel-metal hydride, lithium-ion and other types of power batteries. Therefore, it has great practical value.

On-board lithium-ion power battery system

7. A detailed competition of the world's top ten fastest electric vehicles. How fast can they run?

Today, Electronics Fan Network has compiled the top ten fastest electric vehicles for you. How fast can electric cars run? In fact, they can be faster than you can imagine. Not only pure electric racing cars, but also electric motorcycles, electric boats, electric light four-wheelers, and even bar stool mobile cars are challenging this speed limit.

Figure 1 Fast electric vehicles are powered by pure electricity. Pure electric vehicles use torque technology and do not rely on clutches and gear shifting to accelerate. These advantages have made electric vehicles popular all over the world. Electric vehicles always maintain high speeds without constantly accelerating. This is why electric vehicles always break records.

Figure 2 Electric racing motorcycles In the world of drag racing, the KillaCycle (invented by engineer Bill Dubey) was once king. At the Bundy Miller Speedway in 2008, Bill Dubey's wife ran a 7.955 second lap at 174.05 mph. In October 2010, driver McBride broke the record at 177 mph on the "Rocket," a custom electric racing motorcycle built by Shawn and Orange County Motorcycles. In September, Dubey and Haxon will race an electric motorcycle that looks like a cigar at Pontiac Flats in Utah.

Figure 3 Limited battery space for commercial electric motorcycles has prevented commercial electric motorcycles from exceeding the speed limit of the highway. With the development of lighter and more compact battery manufacturing technology, commercial electric motorcycles have the opportunity to achieve a breakthrough. The EM5000 manufactured by Liberty Electric Bicycle Company is equipped with lithium ion phosphate batteries and can reach a speed of 55 miles per hour. The retail price is $5,500. Zero Motorcycles' Street Cyclone Zero S can reach a speed of 67 miles per hour, with an average speed of 58 miles per hour, and is priced at $10,000.