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Mobile WebSite1. What is the basis for lithium-ion batteries to be safe and green?
The inventor of lithium cobalt oxide, lithium manganate and lithium iron phosphate cathode materials, one of the founders of lithium-ion batteries, is known as the "father of lithium battery" in the industry, and is currently a professor of mechanical engineering at the University of Texas at Austin. Well-known solid physicist, John B. Goodenough, 94, said that "the battery will make significant improvements in the next few years, including battery safety, price, energy density, Service life, charge and discharge speed, etc.
The author understands that lithium-ion batteries will become more and more secure in the next few years. At present, the main basis for the lithium-ion battery to be safe and green is:
(1) Lithium-ion batteries and steam (chai) oil, compared with natural gas, under natural (normal) conditions, will not spontaneously ignite, no leakage.
(2) Compared with lead-acid batteries, under natural (normal) conditions, there is no pollution to air or soil.
Some experts have repeatedly stressed that lithium-ion batteries are not safe, not green. It is an event that may occur beyond the "natural (normal) condition". For example, battery quality is poor, subject to external forces, charging (discharge) and other extreme scenarios.
2. What is the main basis for China's electric vehicles to be safe and environmentally friendly?
(1) China's electric vehicles (new energy vehicles) must use lithium-ion batteries and must not use lead-acid batteries. Ordinary people have already understood and recognized the fact that lead-acid batteries are not environmentally friendly.
(2) China's electric vehicle (new energy vehicle) regulations must be "pure electric drive" mode. Lithium-ion batteries are epoch-making scientific inventions. The types of power used in China's pure electric vehicles are in sync with the advancement of science and technology in the world.
(3) Lithium-ion power batteries purchased by electric vehicle manufacturers are manufacturers licensed by the government. The quality of their products is endorsed by the government. The government strictly controls the power battery manufacturers.
(4) China's electric vehicles use lithium-ion power batteries, which are safe and environmentally friendly. This is relative to fuel (gas) vehicles.
Third, China's power battery package product quality (security) progress with each passing day
Five years ago, electric vehicle production was in small quantities, and the vehicle production technology was not mature. It focused on the verification of engineering application programs and was in the market verification stage. It can be seen from Figure 1 that the harness assembly of the battery pack is relatively simple, the wire extends the pole measurement point to the connector, and the connector is connected to the LECU. Sample line length and patch point. There is a messy sampling harness, and there is a risk that the wiring harness will short-circuit and short-circuit the battery.
Figure 1 Power battery pack five years ago
Five years later, the production of electric vehicles began to be batched, and the production technology of the whole vehicle was basically mature, focusing on the stage of market heavy volume. The modularity of the components is already high. Mainly composed of Module, BMU, PDU, water cooling system, MSD, structural parts, high and low voltage wiring harness, using a circuit board instead of part of the sampling line.
Figure 2 Power battery pack after five years
Fourth, China's pure electric vehicles, the main high-voltage device quality (safety) technology introduction
The following is a schematic diagram of a pure electric vehicle high-voltage system. From the schematic diagram, the main high-voltage devices include battery packs, high-voltage boxes, motors, DC/DC, A/C and other five high-voltage devices. From the engineering point of view, the quality of the high-voltage devices and the quality of the joints are in place, and the safety of the electric vehicles can be guaranteed. The continuous improvement of safety indicators is an eternal issue, and specific issues will be discussed in detail.
Figure 3 Schematic diagram of high-voltage system of pure electric vehicle
Electric vehicles are usually equipped with power systems with more than 300V and currents up to 200A. This is only a 12/24V power system with a conventional car, and its security level is completely different. The high voltage and high current characteristics of electric vehicles may endanger the safety and personal safety of high-voltage components. From the engineering point of view, security measures must be put in place, which are introduced separately below:
(1) High-voltage power distribution box security technology
Figure 4 The shape and internal structure of the high-voltage power distribution box
Everyone with business experience knows that every factory has a power distribution room. A car is likened to a factory, and the high-voltage power distribution box (see Figure 4) is the power distribution room of the factory. The function of the electric vehicle high-voltage box (PDU) is the bridge between the power battery and the power supply and signal transmission of each high-voltage equipment, and detects the insulation fault, open-circuit fault, ground fault and high-voltage fault of the entire high-voltage system at any time. Safeguard measures for safe transmission.
Pure electric vehicle high-voltage power distribution box contains copper row, circuit breaker, air open, contactor, soft start, frequency converter, transformer, contactor, high voltage relay, fuse, surge protector, transformer, ammeter, voltmeter , transfer switch, etc.
a) The basic purpose of designing a high-voltage power distribution box is to ensure the safety of the vehicle, the safety of the driver and passengers, and the safety of the vehicle operating environment.
b) The necessity of designing high-voltage power distribution box: As the energy storage device of electric vehicle, the power battery is affected by the small size of the whole vehicle, the space available is very limited, and the layout is difficult. Therefore, the contactors and fuses of each circuit are used in engineering. When integrated, on the one hand, it can meet the power drive requirements of the whole vehicle, and the second is to facilitate the maintenance of the power battery system, and reduce the need to disassemble the power battery pack.
c) High-voltage power distribution box design requirements: compact device layout, easy to disassemble and assemble
d) The safety measure is to pay attention to the heat dissipation arrangement and prevent the temperature focus from rising.
The high-voltage components connected to the high-voltage power distribution box include: power battery, motor controller, frequency converter, inverter power supply, electric air conditioner, electric defrosting, charging seat, and the like. At present, cast aluminum casing and connectors are generally used, and the degree of protection reaches IP67. The follow-up development trend is toward small size, light weight and intelligent development.
(2) High-voltage connectors and high-voltage harness line safety measures
Traditional connector devices have been difficult to meet their high current and high voltage requirements, and electric vehicle connectors must be high power connection products. If it does not meet the requirements, the electric car will have a fire accident. Electric vehicle connectors must be automotive grade products, and industrial grade products are not up to standard. The main indicators are IP rating, insulation grade, low resistance, error proofing, and locking.
Figure 5 different specifications of high voltage connectors
The wire harness refers to a component in which a contact terminal (connector) made of a copper material is crimped to a wire (cable), and a plastic pressure insulator or a metal case is externally wrapped, and the wire harness is bundled to form a connection circuit. Functionally, there are two types of power lines that carry power for driving actuators (actuators) and signal lines that transmit sensor input commands. The power line is divided into two types: low voltage harness (see Figure 5) and high voltage harness (see Figure 7).
Figure 5 Automotive low voltage wiring harness
The high-voltage harness is the cable between the connector and the connector inside the electric car, and is a very critical connector that supports the safe operation of the entire car. First, it requires shielding, IP rating, overheating or burning. The use of the car is a harsh environment. If it does not meet the requirements, it is the most prone to spontaneous combustion.
Figure 6 car high voltage wiring harness
5. Under the guidance of ISO26262 international standards, Chinese electric vehicles will become more and more secure.
ISO26262 is an international standard for the functional safety of electronic and electrical products used in the automotive industry, such as specific electrical components, electronic devices, and programmable electronic devices. ISO 26262 provides a life cycle (management, development, production, operation, service, scrapping) concept for automotive safety and provides the necessary support during these life cycle phases. The standard covers the overall development process in functional security (including requirements planning, design, implementation, integration, validation, validation, and configuration).
With the development of new energy vehicles in China, the technical level of manufacturers is getting higher and higher. By actively implementing the ISO26262 international standard, the ecological circle of China's new energy vehicle safety will surely form, and people's concerns about the safety of electric vehicles will be gradually eliminated.
