Lithium batteries, in principle, do not charge quickly.

At present, there are more and more articles promoting the rapid charging of power batteries. Some manufacturers 'propaganda is somewhat excessive. Some experts also follow the wind and say that it is even more ridiculous that electric cars can be charged in 30 minutes and 15 minutes. Said it would be done in five minutes. The author expressed concern that these propaganda will be detrimental to the development of the industry, and engineering people understand that "the principle does not understand, the engineering can not pass," and the principle of lithium-ion batteries has told people that they can not be charged quickly.

First ,what is fast and slow?

Car batteries are positive and negative, can charge the battery, there must be positive and negative DC power supply. What do you mean? The alternating current of the power grid can not directly charge the car battery.

But charging an electric car is either 220V for civilian use or 380V for factory use. Why is that? This is the "AC / DC" device used by engineers to turn alternating current into direct current. For the average user, remember:

1 The power supply for charging the car battery must be a DC power supply. The AC power supply can not "directly" charge the lithium ion battery.

2 Where is the DC power supply? At present, the power of the power grid is AC. The direct current that charges the electric car is converted by the "AC / DC" device.

3 "AC/DC" is a device that meets the standard requirements. If this device is installed in the car, the vehicle and charging interface is the AC charging interface; If the device is installed under the vehicle(ground), the vehicle and charging interface is the AC DC interface.

4 AC/DC devices can be made into high-power ones on the ground(Note: The larger the power, the larger the volume and the heavier the mass; The car has insulation requirements and has volume and weight restrictions. Therefore, the AC DC(AC/DC) on the vehicle is of low power.

The concept of "fast and slow" at the first level. The charging speed of the DC interface is faster than that of the AC charging interface. In principle, the DC interface has a charging speed of 3 hours to 4 hours, and the AC charging interface is 6 hours to 8 hours. (Note: The grid can guarantee the supply of 220V for civilian use, or 380V for factory use)

The concept of "fast and slow" at the second level. At present, the theoretical DC interface charging speed is 3 hours to 4 hours, compared with the fuel truck refueling for 5 minutes. Due to theoretical limitations, some experts have proposed the concept of "30 minutes(or 15) charging to 80 %", and there is still 20 % of space. The charging time is ignored. In other words, charge the entire process and segment it.

The concept of "fast and slow" at the third level. The DC interface can not be rapidly powered, referring to 3 % to 99 % of the entire process, fully filled; The DC interface can charge quickly, basically referring to 20 % to 80 % of the entire space. This is part of the lithium-ion battery charging(discharge) curve. Some manufacturers have done some optimization on this curve. In principle, there is no substantial innovation.

Second, the DC interface can not be filled quickly is a comprehensive conclusion, can be filled quickly is a lot of preconditions

Let's start with an example of everyday life. The bucket is used to store water, and the faucet adds water to the empty barrel. The barrel is volumetric(similar to the amount of battery in the car), and the maximum water output from the faucet is also certain(similar to the charging interface). The analysis is as follows:

1,The volume has been determined to add water to the barrel. If you want to hurry, you can turn the faucet on to the maximum.

2,The water output from the tap is certain. If you want to add water quickly, you can make the volume of the barrel smaller.

3,To add water to the barrels that have been determined in volume, the water output from the faucet is also determined, and there is an average(rated) speed for adding water. The average speed comes with the fastest speed and the lowest speed.

Power cells can be quickly charged with logical analysis:

1 The capacity of the car's battery has been clarified. If you want to charge quickly, the physical practice is to add one(or two) more charging interfaces. At present, the 12-meter pure electric bus is this practice.

2 The specification of the charging interface is the national standard(has been clarified). If you want to charge quickly, the basic best practice is to make the on-board battery capacity small, and the lithium titanate charge is faster than the lithium iron phosphate charge. This is the principle.

Third, lithium-ion batteries can not be charged quickly on principle

At present, the battery that can be filled quickly is lithium titanate, but lithium titanate batteries have a ratio of energy to lithium iron phosphate and ternary batteries that is too far away from energy. In exchange for a sentence, the vehicle lithium titanate battery, its range of voyage is too short. Run the same mileage, car lithium titanate battery charging times. The time of a multi-charged onboard lithium titanate battery is longer than that of a slow-filled lithium iron phosphate and ternary battery, and there is no advantage for the user. Can you change the electricity? I can't. Switching electricity also needs to be charged. Switching electricity is more difficult and more expensive than charging.

Electric vehicle power supplement, more than fuel truck refueling speed is too slow, is an objective short board. People are trying to make up for it. How? The author's point of view is that engineering technology(process) must find the solution that the principle is correct, and then integrate the resources(conditions), and do not always try and try again with the idea that the principle is not correct.

The best way is to increase the power cell ratio, that is, a slow charge, and a car can exceed one day(two days, three days) of operating mileage. At present, the power battery is faster than the energy research and development progress, everyone's mileage anxiety, will slowly disappear.

The page contains the contents of the machine translation.