According to the data of 20 19, the top three power batteries in the world are Contemporary Amp Technology Co., Ltd., Panasonic and BYD, among which China enterprises have the second monopoly; In the development of drive motor technology, the total number of patent applications for vehicle drive motors in China ranks first in the world in the past decade. Faced with two such proud achievements, why is there still a gap between China New Energy Vehicle and Tesla, and the listing place keeps shouting "Hard Tesla" but disappears?
In fact, for electric vehicles, the battery, motor and battery management system are like a wooden barrel composed of three boards, and its performance often depends on the shortest board. Today we will analyze it from the perspective of BMS technology. Why can Tesla face the sky in an electric field? Before that, let's briefly understand what BMS is.
BMS is equivalent to the "brain" of the battery.
Battery management system is one of the core systems of electric vehicles. Its main function is to monitor the state of the battery, prevent the battery from overcharge and overdischarge, prolong the service life of the battery, and ensure the safety and cruising range of the electric vehicle.
For example, when an electric vehicle is charging, BMS will transmit the battery charging status signal and related data in real time, which is convenient for the background system to calculate the charging efficiency and evaluate the working state of the battery pack, so as to realize only charging but not charging, prevent overcharging waste and eliminate potential safety hazards, which has dual effects of saving electric energy and protecting equipment safety, especially realizing intelligent charging at high or low temperature. Protecting electric vehicles is of great significance.
Why can Tesla's nostrils face the sky?
The main function of battery management system is to prevent overcharge and overdischarge of batteries, so the estimation of battery remaining capacity is the focus of battery management system research. Because of the nonlinear characteristics of electric vehicle battery in use, it is very important to find an accurate estimation method. The higher the accuracy, the higher the battery cruising range of the same capacity. Similarly, high-precision estimation can also effectively reduce the cost of more needed batteries, which is the main reason why the profit of domestic Tesla is still so rich when it sells more than 200 thousand.
For Tesla, BMS (Battery Management System) has always been regarded as the top secret of its company and the core of all top technologies. At present, most BMS technologies are applied to lithium battery technology. Compared with other batteries, lithium battery pack requires higher voltage for each battery.
Tesla's battery panel consists of 16 battery packs. A battery pack has 444 lithium batteries, and every 74 batteries are connected together, so the whole battery panel consists of 7 104 18650 lithium batteries. The battery used by Tesla is the 18650 lithium battery used in flashlights in life.
In fact, only 96 batteries are connected in series, and only one battery can be connected in parallel, no matter how many batteries you connect in parallel. Our domestic new energy automobile main engine factory only calculates the number of series connections but not the number of parallel connections.
Why is Tesla special? In fact, if you know Tesla's algorithm, you will know that Tesla's algorithm not only needs a lot of calibration data, but also can't guarantee the accuracy of estimation under any circumstances, especially after the battery is aging. Of course, Tesla's algorithm is much better than almost all BMS algorithms in China.
Almost all BMS algorithms in China use current integration plus open circuit voltage to calculate the initial SOC, and then use current integration to calculate the change of SOC. If the starting voltage is incorrect, or the ampere-hour capacity is inaccurate, it must be corrected until it is recharged? Can the starting voltage be wrong? Experience tells us that we will, although the probability is very low. If you want to be foolproof, you can't just rely on the accurate starting point voltage to ensure the correctness of starting SOC.
Tesla is awesome not because its BMS can manage 7 104 batteries, but because its electronic control technology has batteries.
At present, Tesla's battery management system can be said to be the most mature system today. Thanks to its deep learning and full application of artificial intelligence, Tesla's BMS can continuously obtain big data of actual driving, and then self-reinforce the algorithm, thus making Tesla's battery life relatively longer. At present, cruising range is the main problem to improve the penetration rate of electric vehicles, and Tesla shows its differentiated competitive advantage by relying on the leading design concept.
In China, BYD's performance in battery management system is still good. I think if we want to beat Tesla, it is not the slogan of "rejuvenating the country" when the new car comes on the market, but we should conduct in-depth research and overcome technical barriers, so that China can be at the forefront of the world in the field of new energy vehicles!
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.