撰写
The charging speed refers to the speed at which the secondary battery (rechargeable battery) can be recharged. The charging speed depends on the charging rate.
Charging rate = charging current ÷ battery rated capacity
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Example a:
0.2C = 570mA ÷ 2850mAh
The battery was fully charged with 2850mAh for 5 hours, with a current of 570mA(0.57A) and a charging rate of 0.2C.
Example b:
1C = 2850mA ÷ 2850mAh
The battery is fully charged with 2850mAh in one hour, the current is 2850mA(2.85A), and the charging rate is 1C.
Example c:
5C = 14250mA ÷ 2850mAh
0.2 hours to fully charge the 2850mAh battery, the current is 14250mA(14.25A), and the charging rate is 5C.
— — — —
Generally speaking, fast charge is the charge rate greater than 1C, but there is no mandatory standard in the industry, 1C is only a rate that the industry probably agrees with.
Some readers may have encountered the problem that the charging rate of intelligent terminal equipment is too low. It may be that the battery is too hot or too cold, it may be that the battery is aging, or the performance of the charger and charging cable is poor, which eventually leads to the embarrassing scene that the charging speed is faster than the power-off speed. As shown below, my old Sony MP3 player will run out of power when plugged in to listen to music.
Nowadays, the promotion of "charging only takes 10 minutes" in the field of electric vehicles means that the charging rate is much higher than 6C. After all, the first and second stages will slow down, and the comprehensive charging rate will be lower than the peak.
Above 6C? A DC charging pile with a speed higher than 6C is more expensive than your car per minute … …
The process of charging is the process of active lithium ions moving from the positive electrode to the negative electrode. After lithium ions are embedded in the negative electrode, the battery has a higher SOC.
If we refine it again, we can divide the charging process from ultra-low SOC to full SOC into the following processes: A to G, which can be represented by the light purple current curve in the figure below, in which the processes of B and C are the CC Fast Charge in the figure, and the processes of D and E are the CV in the figure:
A. Trickle charging: Because the battery is over-discharged, the internal material is very fragile, so it needs to be recharged first to urge the internal active substances to get up and work. Therefore, an old mobile phone that has been losing power for a long time can’t be turned on just after being plugged in. Try again in five minutes.
B, small current and Constant Current charging: constant current, that is, CC. At this time, the current began to increase and gradually accelerated.
C. High-current and constant-current fast charging: The main stage of fast charging is CC, and the high current is charged to about 80%.
D. High current and Constant Voltage fast charging: constant voltage, namely CV. After reaching the full voltage, the voltage starts to be fixed and the current drops.
E. Low-current constant-voltage charging: the charging current is further reduced, which is the same as CV, until the SOC is fully charged.
F. Trickle charging: SOC is fully charged first (showing full charge), but it can be charged a little slowly. In this process, SOC remains 100% unchanged, which is also what we often call "the most durable 1%". If the mobile phone is plugged in all the time (for example, charging at night), the battery will be charged in pulses, and the charging will stop for a few seconds to maintain the power of the mobile phone at 100%, which is the case with machines in mobile phone specialty stores.
G, full: it can’t be filled at all.
A clever woman can’t cook without rice. If she wants to charge quickly, she must have a robust power grid.
According to the National Bureau of Statistics, China’s power generation in 2020 reached 7.4 trillion kWh, up 2.7% year-on-year, ranking first in the world for 10 consecutive years. According to the data of the International Atomic Energy Agency, China has 26 of the 71 nuclear reactors under construction in the world. According to the World Nuclear Energy Association, China is still planning or planning to build another 180 nuclear reactors.
As a country lacking electricity, the population of India is comparable to that of China, and the power generation is only 1/5 of that of China. Power failure is a very common thing. Recently, the electric furnace of the crematorium in COVID-19 was shut down due to lack of electricity, which was also written as a joke by netizens. The blackout in India in 2001 involving 230 million people and the blackout in India in 2012 involving 700 million people were the two largest blackouts of billion people after the industrial revolution.
In contrast, as the world’s largest industrial country, China’s power generation is unshakable, the proportion of thermal power has been reduced to 70% (and decreasing), and the power grid is extremely stable, paving the way for the electrification of automobiles. This also explains how naive it was to throw the pot at Nanchang Power Grid in Jiangxi Province, and does not consider what kind of hard power the China power grid giants have as an endorsement.
According to the data of China Electric Vehicle Charging Infrastructure Promotion Alliance, by December 2020, the cumulative number of charging infrastructure in China was 1.681 million. According to the data of the Ministry of Public Security, by the end of 2020, the number of new energy vehicles in China has reached 4.92 million, so the "vehicle-to-pile ratio" in China is about 3:1. However, because the capital of charging piles built in the early stage is relatively low, the newly-built fast-charging piles will put forward higher requirements for the load capacity of the power grid, and it is not excluded that some charging stations use more electric power than a whole residential area.
The fast charging of electric vehicles has indeed put forward extremely high requirements for the current urban power grid load. The author tried to consult the residential property on how to install 7kW charging piles for my own parking space, and the property gave the conclusion that it was "unwilling". Although 7kW is only equivalent to two air conditioners, the power grid capacity of each community is very limited. If it is opened to 10 electric vehicle users, it can barely support it. However, if it is increased to 30, the community will trip.
Who will pay for the construction of additional power distribution rooms and various power distribution equipment? Think about it one more step. Will the users who install it first pay for it afterwards and share the overall cost with the users who install it later? These are all unsolved problems for the time being.
At present, the State Grid has basically paved 120kW fast charging piles at major fast charging stations, so it is very good that the actual charging power can be kept above 60kW, and a large part of the power will be divided in the case of one pile with two guns.
In 2016, Musk was bragging that they wanted to build a 350kW SuperCharger V3, but later gave up, and the technology and cost were not allowed for the time being. However, the current landing situation has been able to achieve 250kW, and it is also very good to supplement the 250km battery life in 15 minutes at peak state. Later, the goal of 350kW was relocated to SuperCharger V4.
The 800V system can charge from 0% to 80% in 15 minutes in the experimental stage. The problem is that the charging power as high as 350kW is not affordable for any power grid, and it is impossible to achieve such a terrible charging rate when it finally lands.
Electrify America, a subsidiary of Auto, built the first 350kW fast charging station in California in 2018. The power of a single DC charging pile is as high as 350kW, which can supplement the battery life of 320km in 10 minutes at the earliest, that is, 32km in 1 minute. However, this kind of fast charging station has not been fully rolled out for the time being, because the standard voltage they set is 800V, while the voltage of most electric vehicles on the market is 400V, so some foreign media interpret Electrify America’s move as an environmental protection measure to deal with the negative emotions of the people in the diesel door incident … …
In 2019, Swiss ABB also released a 350kW DC super fast charge, claiming that it can supplement the cruising range of 200km in 8 minutes, and it is compatible with two sets of voltage systems, 400V and 800V, and still works normally in a wide temperature range from-35 C to 50 C. However, because there is no amazing system provided by ABB in China for the time being, we can’t verify how much the actual charging efficiency reaches the PPT.
The most popular thing in recent months is the gust of wind, saying that the new graphene battery can charge the battery to 80% in 8 minutes and reach 1000km battery life.
At the committee of 100 Forum on Electric Vehicles in China (2021), Ou Yangming Gao, an academician of China Academy of Sciences, mentioned in his speech, "If someone says that it can run a thousand kilometers, and it can be fully charged in a few minutes, and it is particularly safe, then don’t believe it, because it is impossible at present." Later, New Energy clarified that 8 minutes and 1000km are two battery technologies, not the same one … …
In fact, it’s not a big problem. As long as Zhong Zhen can charge 80% of the electricity in 8 minutes, it doesn’t need to support 1000km at all, otherwise it’s an extreme waste of resources. What we are looking forward to now is that new energy can realize this fast charging technology more quickly, especially for urban users, fast charging is much more important than long battery life.
Cathode materials have a great influence on the charging speed of lithium-ion batteries. For example, the conductivity of LFP Ferrous lithium phosphate formula is not as good as that of NCM Trilithium formula. Of course, if the surface of LFP cathode is coated with nano-scale materials or a new conductive agent is introduced, the charging rate can be improved to some extent.
The negative electrode material is the main direction of breakthrough in charge rate. For example, in 2019, Contemporary Amperex Technology Co., Limited announced that it is developing a new lithium iron phosphate battery technology. The graphite structure has the characteristics of super fast charge and high energy density by using the "fast ion ring" technology on the surface of the negative electrode graphite. After increasing the lithium ion embedding speed in the graphite layer, it can reach the super fast charge capacity of 4C-5C, which is equivalent to completing the main charging process in 15 minutes.
Another scheme to improve the negative electrode is to adopt graphene structure. Two years ago, the concept of graphene was more popular than the green water ghost, and all kinds of true and false news flooded the Internet. In fact, graphene can’t greatly increase the energy density of the battery as those media people say. It is just equivalent to an internal combustion engine, which can theoretically increase the charge and discharge rate.
But is graphene really a complete scam? Not all of them. Compared with the application in lithium-ion batteries, graphene is more promising to be used in supercapacitors, and its abnormal charging and discharging efficiency can greatly improve the charging and discharging speed. The problem is that the energy density of supercapacitors is only about 1/10 of that of lithium-ion batteries, so electric vehicles using supercapacitors as power batteries only have a very short battery life, and it is ok to get off the feeder bus in the park.
Just now, we also mentioned that GAC New Energy has recently developed a super-fast rechargeable battery with graphene formula. If it can really be put into mass production, it is indeed a breakthrough, because the industry has always thought that graphene additives are extremely difficult to put into mass production.
The fast charge rate can also be improved by starting with electrolyte, because electrolyte involves the migration speed of lithium ions, so we can try to develop electrolyte salts with high dissociation degree or study how to generate SEI films with lower interfacial impedance.
In addition, during the first charging, the electrode material and electrolyte have a complicated reaction at the solid-liquid interface, forming a passivation layer (SEI film) covering the surface of the electrode material and consuming a batch of active lithium ions. Therefore, some batteries will "pre-lithiate" the cathode material and supply the lithium ions consumed by the SEI film first, thus improving the total capacity and energy density of the battery, and avoiding the problem of slow charging speed caused by the lack of lithium ions.
In addition to the positive electrode, negative electrode, electrolyte and lithium ion, we can also charge the production process to improve the charging rate. For example, a more uniform slurry can form a more uniform conductive network between active materials and between active materials and current collectors. Better coating consistency of the pole pieces can make the internal current distribution more uniform and orderly, and higher compaction density of the pole pieces can improve the battery performance.
So what about the solid-state battery that everyone blows so hard? Harm, in fact, this kind of electrolyte is not very close to super fast charging, because the interface contact of solid electrolyte is poor (solid-solid), the conductivity is low, and it is difficult to realize fast charging and the power density is limited.
High-power DC charging pile will use AC-DC and DC-DC to convert the three-phase AC power supplied by the power grid into about 400V-800V DC power. The charging pile needs to communicate with the vehicle electronic control system through data transmission channels (high-voltage control box, vehicle controller, data acquisition terminal, etc.), and the current charging rate is determined by the current battery temperature, SOC and other States of the vehicle BMS. If the battery is bearing a high rate that is not in line with the original design intention, it will reduce the cycle life, and the heat will be out of control and lead to spontaneous combustion.
As the SOC is getting higher and higher, the charging rate that the battery can bear is lower, so when the SOC reaches about 80%, the charging rate should be reduced to avoid damaging the internal structure of the battery.
In addition to the communication between the pile and the car, the charging pile also needs to set up a data channel for online payment, because the charging service is basically impossible to pay with paper money, and this paid data channel must ensure a high level of security and minimize the operating threshold for payment and the possibility of bad debts.
Everyone is born with the ability to eat fast by default, but their tolerance is completely different. Some people will have gastrointestinal problems if they eat fast. In the same way, all batteries have the ability of fast charge and fast discharge by default, but their tolerance is completely different. If a battery that is not designed for fast charge is charged with excessive current, it will lead to a sharp increase in Joule thermal effect, a violent internal reaction of the battery, the electrolyte will decompose oxygen, the structure will collapse, and the expansion bag will spontaneously ignite.
If the battery wants to withstand fast charging, it must have a lower resistance R, which can reduce Joule heat Q.
Let’s recall a formula of Joule’s Law in high school: Q=I2Rt.
Joule heat q is proportional to the square of current I, so once current I is increased, the requirement for heat dissipation will be geometric multiple.
If the resistance r is reduced, it will directly help to reduce q. Therefore, we need to use electrode materials with higher conductivity, use more conductive agents, use electrolyte with better conductivity and so on.
Needless to say, time t will naturally accumulate more heat after a long time.
Of course, a qualified battery temperature control system will not overheat the battery. If it does overheat locally during charging, it may include but not limited to the following three reasons:
1. There is something wrong with the battery temperature control system.
If the heat fails to dissipate in time, just as enthusiastic customers (Li+ ion) occupy various positions and refuse to move their positions, some enthusiastic customers will become dark customers (Li+ion).
At present, many users spend two or three thousand yuan to change the PHEV non-plug-in hybrid vehicle with AC slow charging into DC fast charging, and charge it from the kinetic energy recovery mechanism with higher power. This way has no big problem in theory, and the actual charging power is lower than the kinetic energy recovery power. The problem is that this battery was originally designed for slow charging. If the current density is too high, it is easy to generate lithium dendrites, and there may be problems in heat dissipation (whose PHEV goes downhill for 1.5 hours continuously, which was not included in the original design). The probability of thermal runaway of the battery pack will increase accordingly. Once it spontaneously ignites, there is no manufacturer at the bottom. After all, you modified it privately.
2. The final constant current charging stage is not well controlled.
The lithium ion charging process should be "trickle charging-constant current charging-constant voltage charging-trickle charging-full charging", and the battery SOC is charged at constant voltage from about 80% to 100% (full current), which is relatively slow, and you can feel it when charging your mobile phone and car.
3. Large current causes polarization.
When the high current is charged quickly, too many lithium ions are squeezed out of the negative electrode, which leads to the phenomenon of concentration polarization at the electrode, local overheating, destruction of the electrode material and a pile of dead lithium Li.
The battery is so delicate that it can’t stand being too hot and absolutely can’t stand being too cold. Using fast charge at low temperature will damage the battery, and the lower the temperature, the lower the charging rate that the battery can bear. The mainstream formula that suffers the most at low temperature is Ferrous lithium phosphate LFP.
Then the question is coming. What’s wrong with the low temperature? The high current charging under the premise of low temperature means that a large amount of active lithium is poured in before the negative electrode reacts. The active material inside the battery is lazy at low temperature, and the active lithium squeezes the negative electrode.
Therefore, it is very dangerous to charge with high current in the first stage of trickle charging at very low temperature (battery heating has not yet started), and new energy vehicles with poor electronic control may be at risk when charging quickly in northern winter. In addition, the low temperature in the constant current and constant voltage stage is also a serious problem, so the electronic control of some high-end new energy vehicles will use the temperature control system to preheat the battery, and then charge it quickly with large current to avoid a large number of lithium dendrites growing.
In order to solve the problem of insufficient battery temperature in low temperature environment, there are several solutions in the industry at present:
1. External heating of battery cells: It is the most common to install a heating module at the module or battery pack level.
2. Internal heating of battery core: As shown below, this structure is rare, and it is directly heated inside the battery, but it is only suitable for large power batteries.
3. The heat emitted before the battery is charged and discharged: a natural phenomenon, which was mentioned many times in the previous battery technical article.
4. External internal combustion engine heating: Although the external small internal combustion engine school represented by Weimar sounds funny (a pure tram with an internal combustion engine), you will be grateful for this external … …
"Charging the battery quickly" is not a lie of Pheasant WeChat official account. It does exist, but the degree of harm is not as exaggerated as Pheasant said. In the same way, gasoline and diesel vehicles have a running-in period, but it’s not that they can’t get on the highway during the running-in period. You can drive a new car directly when you buy it. You don’t need any film plating at all. Well, watch the pheasant number less anyway.
If you don’t consider the battery life, you can speed up the charging (as mentioned above). The question is, will you completely ignore the battery life of your own electric car?
"It’s almost done, and it’s a big deal to change another car next month." If you have such a free and easy spending power, why don’t you buy gasoline for a supercar?
Fast charging will reduce the coulombic efficiency, that is, the discharge efficiency, which is the discharge capacity/charge capacity (lithium intercalation capacity/lithium deintercalation capacity) for the positive electrode. The coulombic efficiency of some batteries will be higher than 100% when they are discharged for the first time, but with the formation of SEI film, it will be lower than 100%, and the ratio will gradually decrease with the increase of cycle, and the activity will become weaker and weaker.
Because fast charging will change the active lithium ions that can’t be embedded in the negative electrode into dead lithium, with the decrease of active lithium ions, the coulombic efficiency will gradually decrease, and the discharge efficiency is not as good as that of new batteries, which is reflected in slow charging, less storage capacity and lower discharge power.
At present, most electric vehicle modifications do not belong to "car modification", but should belong to the lowest "car makeup". If the electrical circuit is not moved, the impact is not great, but the wind resistance is greater and the battery life is lower, which is basically pollution-free.
The most troublesome indigenous modification is the PHEV plug-in model "changing from slow charging to fast charging". The principle of this grassroots modification method is to use the electronic controller interface in the engine room to access the kinetic energy recovery system, and use the only high-power kinetic energy recovery line in the whole vehicle for fast charging, and the maximum charging power can be changed to 30kW.
No matter whether the power battery has fast charging ability or not, it actually has high-rate charging and discharging ability, but the damage condition is unclear. The battery with fast charging ability can charge and discharge quickly more times, and the battery without fast charging ability can only "lose its life", as mentioned above.
The problem is that because the high-voltage device is modified privately, and these private scientists who only need 3000 yuan for the full set of "personalized customization" services have not given the matching insulation upgrade service, the process of plugging and unplugging the DC fast charging plug is very dangerous, not to mention the rainy day or going back to the south.
For pure electric vehicles, if the electric vehicle with 400V voltage platform wants to increase the charging limit, it can be boosted to 800V voltage platform by replacing the cooling system, capacitor, IGBT and upgrading the insulation level. However, these processes are completely impossible for individuals and quick repair shops, and manufacturers will not specifically make such an upgrade program.
After being upgraded to 800V, the insulation requirements will rise, so when you plan to lift a charging cable of Porsche 800V fast-filling pile, you will find that male car owners have the strength to tame this black dragon made of rubber … …
It’s simply hooliganism to say that it is quick to charge without talking about the cost.
For a medium-sized fast charging station (10 piles), the land acquisition cost is about 2 million, the infrastructure cost is about 4 million, and the supporting facilities cost is about 1 million, which adds up to almost 7 million yuan.
The construction cost of 60kW DC fast charging pile is about 70,000 yuan, and the construction cost of 120kW DC fast charging pile is about 130,000 yuan. If you want to invest in 250kW or even 350kW charging pile, then "pile is more expensive than car" is also possible.
At present, it is very good that the DC fast charging rate reaches 1C, while the peak charging rate of 350kW DC fast charging is as high as 3.5C (assuming that the high-capacity high-voltage battery pack is 100kWh), which is beyond the affordability of most manufacturers and consumers.
Because of its high efficiency and great potential, wired charging is bound to be the most mainstream way to charge electric vehicles, and DC fast charging is the realization form to improve the charging rate.
Private piles can’t afford 180,000 yuan for high-power DC fast charging, but the highest-power private piles currently on the market are the previously released 20kW household charging piles (DC). Although the slow charging time can be shortened by two-thirds, it needs 380V three-phase electricity, and the installation price is as high as 16,800 yuan, and most communities can’t provide such a high load. Considering that many owners of Weilai own single-family villas, this 20kW fast charging set is quite valuable for development.
Public piles are operational and can serve a large number of new energy vehicle users, so the cost sensitivity is not so high. At present, the mainstream power of public piles under construction is 120kW, and the industry is rushing to 250kW, while the next two steps are 350kW and 500kW.
500kW is a very large power value, that is, the extreme value of a Porsche 911 GT2 RS at full power output, how much influence it has on the power grid load and how terrible the heat generation is, and we can know it by a little estimation.
In addition, wire is also very important. We usually know it when we buy a fast charger for mobile phones. If it is equipped with an old-fashioned charging cable, for example, it can only pass 2A current, then the power will be 5V×2A=10W, but now the mobile phone charger has at least 22W to barely call fast charging. With the increasing voltage, current and power, the wire will become heavier and heavier, and adult men may not be able to lift it.
After the automatic driving technology matures, wireless charging will break away from the ranks of chicken rib technology and gradually become a reality.
At present, the mainstream wireless charging methods for new energy vehicles are as follows:
As can be seen from the table, the transmission power of wireless charging is very low, so at present, the highest power wireless charging equipment can only recommend charging PHEV plug-in hybrid vehicles.
In the field of new energy vehicles, the current wireless charging standards are complicated. Let’s take two giants as examples. One is TIR J2954 released by SAE of American Society of Automotive Engineers, which is said to have the highest energy transmission efficiency of 85% (currently, it is a castle in the air) and has four power levels, namely 3.7kW (WPT1), 7.7kW (WPT2), 11kW (WPT3) and 22 kW. At present, we are playing WPT1 and WPT2.
The other is the result of cooperation between China Electric Power Research Institute (CEPRI), China Automotive Technology and Research Center (CATARC), China Electric Power Enterprise Association (CEC) and WiTricity Company mentioned above, and the Chinese national standard GB/T 38775 Wireless Charging System for Electric Vehicles.
The first four kinds of power in the national standard are consistent with SAE standard, followed by WPT5-7, in which the charging power of WPT7 is more than 66kW, which is considered as fast charging for wired charging.
Just now, we mentioned graphene and supercapacitors. If we don’t consider the storage capacity of a single charge, supercapacitors can really achieve a very magical fast charging effect, which is really super fast charging in seconds.
It’s just that such a small amount of electricity storage is only enough for cars to run a short distance, and it is also possible to make the park connect with buses, stop at stations and charge at stations.
The power exchange station with the same Bug is actually not built by Weilai, and some operating vehicles are also in use, such as the Beiqi New Energy Power Exchange version taxi operated in Beijing.
The logic of changing the power station is to transfer the charging time and space during the period when the battery fast charging technology and energy density cannot be fundamentally broken, and put a new battery pack on the car like a magazine.
Although it has been criticized by the industry (as if it were a spray of money), it has to be admitted that changing electricity is the fastest way for electric vehicles to obtain electricity.
The fuel cell scheme represented by hydrogen fuel is another scheme to solve the charging speed problem.
As shown below, hydrogen is stored in the hydrogen storage tank, and the fuel cell stack is responsible for converting hydrogen into electric energy, which can enter the small storage battery or directly drive the motor.
The advantage of this scheme is that hydrogenation only takes about 5 minutes, which is close to the current gasoline and diesel vehicle refueling market. The difficulty is that the construction cost of the hydrogen refueling station is 15-20 million yuan, which is only suitable for point-to-point commercial transportation routes at present.
In addition, hydrogen fuel cell vehicles cannot be popularized, and political reasons dominate. You can see that Japan has no allies in the world, and it is basically a plastic relationship. Japan wants to promote MD players, and China and the United States immediately industrialize MP3 players. Japan wants the whole plasma TV, and China and the United States immediately put the LCD industry chain together; Japan wants to develop hydrogen fuel cell vehicles together with South Korea, and China and the United States directly engage in pure electric & HELIP; …
Therefore, China and the United States, which have the strongest fight, are not really what everyone sees. In the final analysis, it is all driven by national interests.
The flow battery scheme is actually similar to the fuel cell scheme, except that the energy density of the flow battery is too low.
The brand has released several liquid flow battery cars before. Using the top view of QUANT E, it can be seen that the positive and negative electrolyte cylinders of 200L are distributed in the middle and rear chassis of the car body (QUANT E is 250L on the left and right), and the electrolyte flows into the fuel cell to generate electricity, which is finally transmitted to the four-wheel motor through the super capacitor.
QUANT E came to the electrolyte replenishment station carrying a total of 250L×2=500L waste liquid. The first thing to do was to unload the waste liquid that was to be transported back to the factory for reconstruction, and the second thing was to load fresh electrolyte. The question is, how efficient are bilateral infusion institutions that work at the same time?
The author assumes that the diameter of the single-side infusion tube is 5 cm ㎡ = 0.0005 m ㎡, and the single-side liquid tank is 250 l = 0.25 m, so it is necessary to transport 500m long electrolyte at one time. Estimated at the speed of 1m/s, the liquid is drained for 8.3 minutes and rehydrated for 8.3 minutes. It is still ideal.
In the power storage device, the fast charging ability of the battery greatly improves the energy utilization efficiency of the power station, accelerates the instantaneous response speed of the power grid and reduces the loss.
It takes a very long period for fast charging technology to go from laboratory to mass production, but many media (not journalists) always make some exciting fake news in order to grab headlines, and generalize the technology of laboratory samples as the technology of mass production products.
According to the above news, one car is filled in one minute. What power charging device is this? The charging rate is 60C, and the charging power is 30000kW (assuming the battery pack is 50kWh). I’m afraid the charging cable will be lifted by a crane. If the charging station charges 10 vehicles, the power system of the aircraft carrier Kitty Hawk needs full power operation to barely maintain … …
Can some media people learn a little about junior high school physics before making up news?
At present, about 60% of the fire accidents of new energy vehicles are caused by the thermal runaway of the battery itself, about 30% are charging accidents, and only about 3.6% are due to the impact in driving accidents. Therefore, consumers may as well pay more attention to charging safety if they are worried about accidental spontaneous combustion.
The mechanism of thermal runaway (generally referred to as "abuse" in academic circles) can be divided into two major directions: physics and electrochemistry, and 30% of the charging accidents may be caused by physics or electrochemistry.
Since January 1, 2021, the new national standard GB 38031-2020 "Safety Requirements for Power Batteries for Electric Vehicles" has introduced many kinds of safety tests, including over-discharge, over-charge, external short circuit, heating, temperature cycling and extrusion tests, and vibration, simulated collision, extrusion, moist heat cycling, immersion, thermal stability and temperature shock tests for battery packs or systems.
In addition to physical abuse such as impact or immersion, many tests including heating, temperature shock, thermal stability and overcharge are related to fast charging. With the increasing charging voltage and current (nonsense, P=UI who can escape), fast charging will be the main cause of fire accidents of new energy vehicles for a long time to come, and the safety impact of design, materials and workmanship problems of cheap models will be amplified.
Commercial vehicles have always lacked space to carry battery packs, so there is a huge number of batteries and huge power consumption, followed by huge security risks. We must know that any battery cell inside the battery pack is out of control, and there is a high probability that it will "catch fire".
To charge commercial vehicles, charging stations/charging piles are required to provide an order of magnitude higher power supply capacity. If thermal runaway occurs during fast charging, it will be an order of magnitude more difficult to put out the fire.
Can Huawei Xiaomi Meizu’s fast charging technology be used in the field of power batteries?
That … … Consumer grade and vehicle regulation grade are not the same concept, and there is a difference of three orders of magnitude between 120W fast charging and 120kW fast charging … …
How many successful cross-field cars have been built at present? The automobile industry is the apple of the eye of the country’s heavy industry, and many technologies cannot be exported. Do you think those amateurs who have never set foot in other fields of the automobile industry can learn it in a short time?
Therefore, we will see that many cross-field car-making enterprises have produced a lot of industrial waste, treating the first batch of consumers as white mice providing operation data, and they will not be spared from the pits that established car-making enterprises have been in for a hundred years.
Please keep in awe of building a car. This is a highly sophisticated knowledge that is very difficult to master and can be quickly "converted from civilian to military". Don’t forget that Ford used to produce bombers, Cadillac is an expert in tank production, and Volkswagen has an unclear relationship with cruise missiles.
Neither charging pile enterprises nor charging pile operating enterprises have a particularly strong willingness to promote super-fast charging piles.
On the premise that the market is not mature, the construction cost of the super-fast filling pile with a charging rate of 5C or even higher is extremely high, and the return on investment is very long (although fast filling can improve the turnover rate of customers), so who will do the first batch of crab-eating business at a loss?
Fast charging only has a relatively low consumer perceived cost, because fast charging piles are not exclusive to them, and the battery life is determined by their own high-voltage battery packs. Therefore, consumers are more willing to spend a lot of money to buy a pure electric vehicle with long battery life, but not so willing to spend a lot of money to buy a super fast charging service for a shorter time. After all, some fast charging is just Schrodinger’s fast charging … …
At present, more and more PHEV plug-in hybrid vehicles are equipped with DC fast charging devices with low charging rate, which is a good thing. (The picture below shows PHEV changing from slow charging to fast charging, which is very dangerous.)
For consumers, fast charging can make PHEV use more electric energy to drive, use less fuel and reduce fuel consumption cost.
For car companies, the fast charging function of PHEV can enhance the sales potential.
For charging pile enterprises, the previously installed DC charging piles with low charging rate will not be abandoned, but will continue to be used in PHEV field, which also provides construction funds for higher power super charging piles.
For the country, using more electricity and burning less oil can further improve China’s energy security.
Super fast charging represents the ultra-high infrastructure cost and relatively short charging time, so the overtime occupancy fee is a very necessary charge for scarce resources. Without this fee, the user experience of fast charging service will become very bad because of the selfishness of some users.
Take Tesla’s current overtime occupancy fee standard as an example. If the current free parking space of the charging station is less than or equal to 50%, and the current user still occupies the charging parking space for more than 5 minutes after the charging is completed, Tesla will charge 3.2 yuan the overtime occupancy fee per minute. If the current free parking space at the charging station is 0, the fee will be raised to 6.4 yuan per minute.
This is not a special charge for users in China market. In fact, Tesla users all over the world have to pay this penalty.
On the one hand, fast charging can reduce endurance anxiety, reduce the capacity of power battery, reduce the weight of the whole vehicle and then reduce the power consumption per kilometer, which can be described as energy saving and environmental protection.
On the one hand, fast charging will reduce the charging efficiency, and excessive electric energy will become useless heat. In addition, it will accelerate battery aging, reduce battery life, accelerate the formation of lithium dendrites, and cause the risk of spontaneous combustion. In addition, super fast charging will greatly increase the load on the power grid, which requires a lot of social resources to build infrastructure facilities.
Therefore, fast charging can not directly refer to environmental protection, it has two sides: environmental protection and non-environmental protection.
In addition, many manufacturers have speculated on the environmental protection characteristics of V2G reverse charging before. In fact, this scheme that consumes the cycle life of power batteries heavily is not environmentally friendly at all, because there will be serious pollution during the production and recycling of power batteries, and there is basically no winner in the scheme of using electric vehicles to store energy for the power grid.
The biggest weakness of electric vehicles is that the bottleneck of battery technology can’t be broken, and the habit of using cars (filling oil in 3 minutes) that has been developed in the automobile society for more than 100 years is not compatible with it. Fast charging will be another feasible solution besides energy density. Car companies that talk about the future of electric vehicles without energy density and fast charging are basically untrustworthy.
At the end of this dialectical thinking, this long article of ten thousand words officially ended.
(Photo/Text/Photo: Pacific Auto Network Huang Hengle)