In recent times, the automobile industry in China or other overseas countries has been moving towards the era of electrification and electrification without exception. However, with the gradual advancement of EVs, there are also many problems, the most significant is the problem of endurance anxiety, energy anxiety problem - whether it is the chaos of queuing for several hours and waiting for a charging position on the eleventh of last year, or the embarrassment that electric vehicles dare not open the air conditioner on the road during the Spring Festival, and dare not drive a fast car to "climb" on the road, all of which explain to everyone that endurance anxiety and energy supplement anxiety are not only anxious in the heart, for some people, even this anxiety will be manifested in body language.
The reason why gasoline cars do not have such a strong problem of refueling anxiety is because the refueling (that is, refueling) is convenient enough, when the oil lamp is on, in general, in the territory of Chinese mainland, within 20 minutes (especially remote areas may not be so) can find a gas station, only a few minutes to fill up the gasoline, and can travel hundreds of kilometers, which is "no anxiety".
(This is the number of gas stations within the city limits of Lhasa)
However, electric vehicles are not so lucky, when the battery lights are on, only 50km of battery life is left, not only to worry about where to find the charging station, but also to worry about the problem of direct high-voltage power outage when the table is 50km due to improper settings of some BMS systems. In addition, charging from SOC 0 to 100% is not a matter of moments or minutes, and waiting will further lead to a worsening of anxiety. From this point of view, increasing the density of charging stations or improving charging efficiency, so that charging can also be like refueling, adding hundreds of kilometers of endurance in a few minutes, is an effective solution to alleviate the anxiety of charging and replenishment. How to improve the density of charging stations let's put aside, this issue we will talk about how to make the charging process faster and more efficient.
Charging electric vehicles is actually to move the electrical energy in the power grid to the battery pack of the electric vehicle through the intermediate substation channel and store it. In the middle of this, we have to go through several links such as power grid, cable, substation, and car charging cable - the first few links do not need us to worry, we only care about the car charging cable and vehicle.
1
Increase the charging voltage
Reduce current to reduce losses
The electricity we use now is actually delivered using the principle of ultra-high voltage transmission (110kV), which is itself a means of improving the transmission efficiency by increasing the voltage and reducing the current, and the same is true for car charging.
Let's first look at a formula: (P stands for power, U stands for voltage, I stands for current)
P=U· And
Divide the U item to the left and it becomes
I=P/U
That is to say, in the case of a certain power, the voltage and current are inversely proportional, that is, the higher the voltage, the smaller the current; on the other hand, when the current remains unchanged, the higher the voltage, the greater the power. So what does this mean for electric vehicle charging? First of all, in the case of the rated charging power is unchanged, increasing the charging voltage can reduce the charging current, which will make an important contribution to the level of cable loss. When the electric vehicle battery is charged, its role in the circuit is actually to use electrical appliances, just like bulbs, motors, etc. are absorbing energy, and the cable that transmits electrical energy for it has a certain resistance value, and its equivalent circuit principle is similar to the following:
(to the negative electrode) - positive electrode - electrical appliances (automobile) - cable internal resistance - negative electrode - (positive return)
Therefore, the resistance of the electrical appliance itself and the internal resistance of the cable will lose the energy output by the power supply, and it will be dissipated in the form of heat, forming an energy loss, and this loss cannot be avoided. The heat generation of the circuit and the current have this relationship:
Q=I2· R·t∝I2∝I (∝ proportional to)
It can be seen that in the case of a certain resistance value, the smaller the current, the less heat generated due to the internal consumption of the cable, and the smaller the ability of the power grid to transmit to the battery of the electric vehicle, which improves the utilization rate of the energy of the line network to a certain extent and improves the efficiency of charging the electric vehicle.
Please note that the contents of the upper and lower sections do not contradict each other, they are two sides of the charging thing
2
Within the allowable capacity,
In the case of constant current
Increase the voltage to increase the charging power
With the above P=U · As a basis, you can also increase the charging speed by increasing the total charging power while keeping the current constant. At present, "high-voltage platform models" such as BYD Han and Porsche Taycan are based on this principle. Taking Porsche as an example, by setting the high charging voltage within the allowable range of the substation capacity, the charging power is completed as high as possible under the unified cable specifications to achieve the purpose of rapid power replenishment. At present, domestic car companies, including Sharon Automobile and Extreme Kr (although the 800V platform was finally abandoned), many of them are making efforts at this level.
3
Crazy ideas:
Superconducting vehicle charging cable, it is really possible to achieve
Combined with what we just said about cable heating: Q=I2 · R·t, it can be found that the heat generation is not only related to the current, but also to the resistance value. The thermal Q is proportional to the square of I, and the first square of the resistance value R already has a proportional relationship, and the variable I is one order higher than R, that is, the influence of R on Q is more direct than the influence of I on Q.
Therefore, by reducing the resistance of the transmission cable, it is also a good way to reduce heat loss. When it is close to absolute zero, the resistivity of some metals will drop to 0, which means that the internal consumption of the transmission cable disappears. According to the Q=I2 just now· R·t, R0, Q0, because a multiplier of 0, the product is 0. Then once the cable material achieves superconducting transmission, the efficiency will reach 100%. This is the so-called crazy idea, referring to the superconductivity principle of mrI devices, I guess it should not be a big problem to create a superconducting environment for cables.
(The following is the Baidu introduction of superconducting cable)
Summary: In summary, increasing the charging voltage and reducing the internal consumption of the cable are good measures to improve charging efficiency. We hope that some domestic car companies will vigorously advocate that "charging is more convenient than refueling" and "where oil trucks can go X can go", they will seriously study from the most basic principles, rather than relying on MLM brainwashing every day to get by.
We predict that if the superconducting cable can land on the vehicle charging, the waiting time for electric vehicle charging will be further shortened, the occupation time of the charging pile will also be greatly reduced, the speed of "overturning" can also be greatly accelerated, coupled with the accelerated layout of the charging pile, the era dominated by electric vehicles may really come soon.
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