In the face of the current tens of millions of electric cars, how much of our money is spent on car purchases, and how much is used to buy batteries? The battery is the heart of electric cars, its good or bad will Directly affecting our normal travel, the biggest problem with fuel vehicles is the safety of the battery and control circuitry. Therefore, it is a top priority for its maintenance work. For the electric car that moves hundreds of thousands of dollars, you must first understand the problem of its core components (battery), and understand clearly to buy it.
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Life mileage
Lithium-ion batteries are relatively sensitive to temperature, and the temperature can be said to be the killer of lithium batteries for electric vehicles. Generally, the operating temperature range of lithium batteries is concentrated between -20 ° C and 200 ° C. However, the temperature sensitivity of lithium batteries of different material types is also different.
Among them, the lithium iron phosphate battery, which is currently the most widely used in China, has better high temperature performance, but lacks tolerance for low temperature. For some better quality products, only 80% of the electrical energy is released at -20 °C, and below -40 °C, the battery is often "frozen" and irreversible damage to the internal material crystallizes. Although some manufacturers have developed lithium iron phosphate batteries doped with manganese or olivine crystal structure, they can cope with lower temperatures, but they will also have more discounts in power and cruising range, and higher costs.
Lithium batteries of ternary materials and lithium cobalt oxide materials are sensitive to high temperatures in addition to low temperature (below -40 ° C) discharge decay. When the operating temperature exceeds 220 ° C, it will cause irreversible damage to the battery structure.
In the low temperature environment, it is also shown that there is a long cruising range before starting, and the value is greatly reduced immediately during driving, which is often caused by the low actual battery output of the battery. In a high-temperature environment or continuous driving for a long time, if the battery cruising range is sharply reduced or the current is interrupted, there may be a problem that some of the batteries have heat dissipation, and the protection system turns off some of the batteries with excessive temperature. Therefore, in use, consumers should pay attention to the use environment of electric vehicles, but also pay attention to keep the front grille clean, so as not to cause poor heat dissipation.
2. Battery spontaneous combustion
When the outdoor temperature is 38 ° C, the surface temperature is estimated to be close to 60 ° C, which means that the season when the vehicle is most likely to break down comes. Electric cars are inherently safe. For the self-ignition accident of lithium batteries that people are worried about, with the improvement of battery technology and the improvement of technology, it has rarely happened in recent years.
Even if it happens, it is the extreme situation that occurs after the vehicle has suffered a serious traffic accident, resulting in the disintegration of the vehicle and the failure of the battery safety protection system. Moreover, the self-ignition of the lithium battery is also related to the battery material used. The lithium batteries of our mobile phones, charging treasures and electric bicycles usually use lithium batteries of ternary materials or lithium cobalt oxide materials. These batteries are affected by the thermal instability of the materials, and when they are subjected to high temperatures, they emit flammable substances. This causes the battery to ignite or even explode. For the lithium iron phosphate battery widely used in China, the thermal stability is good, and no combustible material is generated even under the condition of overheating and impact. Therefore, there is no need to worry about the self-ignition of lithium batteries in electric vehicles.
3. Fast and slow charging
The charging mode of electric vehicles includes slow charging and fast charging.
For more than 20 kWh of battery energy, it takes about 8 hours to use the ordinary power supply from the battery to fully charge from the battery to the full charge, which is obtained under the test conditions. It is impossible to use zero battery power in daily driving, and the lowest is the remaining 10% to 20%. In other words, it can be fully charged in about 6 hours in normal use.
However, for most car manufacturers, it is not a good idea to use this fast charging method too much. Because shortening the charging time means that according to the law of conservation of energy, it is necessary to increase the charging current and voltage, and charging with a large current and voltage will cause a certain voltage shock and overheating danger to the battery, resulting in irreversible battery structure. damage. Greatly affect the cycle life of the battery.
In slow charging, the cycle life of the battery can usually reach more than 2000 times. In the case of fast charging, the cycle life will be quickly shortened to less than a thousand times or even lower. Fast charging is not only an increase in electricity bills, but also a significant increase in battery breakage costs. For most car owners who are pursuing economic use, fast charging is better used temporarily in emergency situations.
4. Insurance
As a key component of electric vehicles, batteries account for roughly 30% of the total price. For electric vehicles, it is difficult for insurance companies to introduce insurance programs that are solely for battery damage. Even in the case of vehicle damage insurance, compensation for battery damage is not included. The main reason why batteries are difficult to cover is that insurance companies are difficult to judge the valuation and damage of power lithium battery products used in electric vehicles, which makes it difficult for insurance companies to predict risks and set premiums.
Specifically, first, the composition of a lithium battery of an electric vehicle is complicated. Since the lithium battery system is usually composed of a positive electrode material, an electrolyte, a negative electrode material, a protective case, an electrode lead, and a battery management chip. These components are typically millimeter, micron-sized devices. Among them, problems in each part may cause damage to the battery. As an ordinary electric vehicle, the battery pack usually contains hundreds of such single cells.
The use of ambient temperature is too low and too high can cause the lithium battery to be denatured from the internal material, causing the entire battery to be damaged or the performance is greatly reduced. Too bumpy roads or car bottoms can also cause the battery to be subjected to violent bumps and damage to internal structures. Too much humidity or wading can cause water in the battery or corrosion of components.
The most deadly is that the battery damage caused by these factors often cannot be attacked at that time, but gradually accumulates and gradually deteriorates during use. This makes it difficult for insurance companies to determine the immediate risk of battery damage. Finally, there are many types of lithium batteries used in current electric vehicles, and the production of power lithium batteries lacks national uniform standards. Even the same model, the same manufacturer's car and battery are inconsistent.
Battery materials vary widely, battery quality is uneven, and standards are missing, making it difficult for insurance companies to determine the actual value of batteries and maintenance costs. It is even more difficult to distinguish between damage caused by product quality or accidental damage caused by vehicle owners.
At present, due to the lack of lithium battery technology, industry level and corresponding judgment standards, the damage determination and insurance for lithium batteries of electric vehicles is still a problem.
5. Warranty
In response to consumer concerns about the quality and service life of electric vehicle batteries, various electric vehicle manufacturers have introduced battery manufacturer warranty commitments. Some promised 100,000 kilometers in 5 years, the battery quality problems were replaced free of charge, and some promised 150,000 kilometers in 6 years. BYD even proposed a permanent free replacement of battery quality problems.
In fact, we found that on the one hand, the larger the scale and the stronger technology, the longer the mileage and the age of the battery warranty. On the other hand, we find that there is still a lack of detail in these commitments.
The first is how to determine that the battery has been quality problems, there is no clear standard here. Intuitively, if the battery's cruising range is greatly reduced in the short term, or the battery power suddenly decreases during driving, it can be used as evidence that the battery has already had problems. However, these intuitive phenomena lack corresponding technical data as a criterion.
In addition, how to determine whether it is a battery quality problem or a consumer's improper use of the fault is also a problem.
If, when the battery fails, you find the manufacturer's request to honor the warranty and replace the battery for free, the manufacturer replies to you. In your vehicle insurance, there was a vehicle wading or bottoming repair two years ago. If you use a malfunction caused by improper use, then who will judge as a third party?
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