[YesAuto Electric Vehicle] How to improve the battery life of pure electric vehicles? In order to solve this problem, manufacturers have “armed the teeth” of pure electric vehicles, such as continuously improving power battery technology, continuously reducing wind resistance, and even adopting so-called “low wind resistance wheels” for the wheels. In terms of improving battery life, there is actually another technology that we must not ignore, and that is kinetic energy recovery. In addition to making a pure electric vehicle drive, it will have a completely different feeling from that of a fuel vehicle. Do you know its past and present, and the benefits it brings to us?
● F1 is also equipped with kinetic energy recovery system
Before talking about the kinetic energy recovery of pure electric vehicles, let's take a look at the three types of energy recovery examples. They are different in nature from pure electric vehicles. They apply different technical principles and logics, and also obtain and achieve different effects and goals. But they are all plans to “recycle the energy that would have been wasted.” For example, F1 introduced the “mechanical flywheel kinetic energy recovery system” in 2009. Its purpose is to store energy through technology. When the vehicle needs more power, the energy is released in a short time. This is the same as the kinetic energy recovery used by new energy vehicles today. The nature of the system is different.
The principle of the mechanical flywheel kinetic energy recovery system is simple. In layman's terms, we can understand the flywheel as an energy storage device, similar to the spring of a children's toy car. When the vehicle brakes for kinetic energy recovery, the kinetic energy is transmitted to the flywheel through the continuously variable transmission, and the flywheel accumulates energy through high-speed rotation.
Judging from the system structure diagram, the system also requires multiple components such as continuously variable transmissions and gear sets as auxiliary components. Isn't this an increase in the process and the weight of the system in vain? The flywheel needs to increase the kinetic energy stored by increasing its rotation speed. For example, the maximum speed of the mechanical flywheel developed by Flybrid has reached about 60,000r/min, which obviously cannot match the engine and wheel speeds, so an “infinitely variable speedless gearbox” is needed in the middle. To transfer kinetic energy.
In addition, in order to achieve the purpose of not wasting the kinetic energy of the engine and releasing the kinetic energy, an axle-side clutch is also provided on the drive shaft connected to the stepless gearbox. When there is no need to recover kinetic energy, the clutch is disconnected and the flywheel does not recover kinetic energy; when the kinetic energy stored in the flywheel needs to be released, the clutch is engaged, and the kinetic energy of the flywheel is combined with the engine power at the output of the main gearbox through the gear, and then the power is transmitted to the drive wheel.
We can find that there are no motors and batteries in this system. This is because F1 must consider the weight of the car. Therefore, the energy stored by the mechanical flywheel is limited, and the time for releasing kinetic energy is often within 10 seconds. This is suitable for short racing cars. The power increase within time, but not suitable for civilian vehicles.
● Examples of hybrid vehicles using kinetic energy recovery
F1's mechanical flywheel cannot store much energy, but the new energy model itself needs to be equipped with a battery pack. Isn't this just a place for the recovered kinetic energy? Including pure electric vehicles and hybrid vehicles, battery packs have become the home of kinetic energy. Hybrid models have an engine, which can recover the kinetic energy of the engine, such as Toyota's THS hybrid system. To avoid the waste of kinetic energy, the improvement of vehicle energy efficiency means the reduction of energy consumption, so the economic performance of new energy vehicles should be said to be inseparable from the help of kinetic energy recovery technology.
Roughly speaking, the E-CVT gearbox of Toyota's THS system includes an MG1 generator and an MG2 drive motor. When the engine is in excess power or at idle speed but does not require power output, the kinetic energy is converted into electrical energy through the MG1 and transmitted to the battery pack; when the vehicle needs power output, MG2 acts as a driving motor to assist the engine to output power; in addition, MG1 has a The additional function is speed regulation, which makes the engine work as far as possible in the economic range, which has nothing to do with kinetic energy recovery, so we will not talk about it in detail.
● Add a kind of “wonderful kinetic energy recovery”
Whether it is mechanical flywheel kinetic energy recovery or engine kinetic energy recovery, they all recover the energy of the “drive part”. In fact, in a broad sense, the kinetic energy recovery system also includes the form of absorbing body bumps, which is called the “body hydraulic kinetic energy recovery system.”
When the vehicle goes through bumps, there is kinetic energy when the vehicle body moves up and down. In principle, the hydraulic kinetic energy recovery of the vehicle body recovers this part of kinetic energy and converts it into electrical energy or other energy to drive the vehicle. Generally speaking, this kind of kinetic energy recovery system is equipped with a piston hydraulic pump. The up and down movement of the body will press the hydraulic oil into the energy storage tank. When needed, the pressurized hydraulic oil can drive the generator to generate electricity, so as to achieve the effect of kinetic energy recovery and reuse. .
This kind of kinetic energy recovery method is not groundless. In fact, around 2015, Audi released a chassis suspension system called electromechanical Rotary Damper (eROT). This system uses electromechanical rotary shock absorbers instead of traditional ones. Hydraulic shock absorber. Audi has tested the system, and its energy recovery power is about 3-613W on three different road conditions: highways, country roads and the Nürburgring race track.
● Kinetic energy recovery of pure electric vehicles
Pure electric vehicles do not have the engine of a hybrid vehicle, so its kinetic energy recovery is achieved through the electric motor, and pure electric vehicles are equipped with a larger capacity power battery pack, so the power battery naturally becomes “kinetic energy.” Destiny”. At present, the kinetic energy recovery system adopted by most pure electric vehicles is called the “battery-motor kinetic energy recovery system”. As the name suggests, it relies on batteries and motors to achieve the purpose of recovering kinetic energy.
We all know that a motor is a process of transforming electrical energy into mechanical energy, which is called electromagnetism. When two magnetic fields are energized, mutually repulsive or mutually attractive forces are generated to realize the operation of the motor; the motor can act as a generator at the same time, the principle is opposite. It is a process in which electromagnetic induction and mechanical energy are transformed into electrical energy.
When the driver releases the accelerator pedal, the motor does not need to work, and it starts to act as a generator. At this time, the mechanical energy of the vehicle is converted into electrical energy by the generator and charged into the battery pack. When the generator is working, the two magnetic fields also produce a certain torque. This force is opposite to the force output by the motor, which realizes the “reverse drag of the motor” and the vehicle has a deceleration effect.
By the way, the main function of the kinetic energy recovery system is to reduce the waste of kinetic energy and increase the cruising range. In addition, because it can decelerate the vehicle, it also reduces the frequency of use of mechanical brakes and protects the brake system to a certain extent. In civilian vehicles, this may not be of much significance, but it is also the principle of using the motor reverse drag. It plays an indispensable role in the “Big Mac” of NTE330, because traditional mechanical brakes cannot withstand the inertia brought by such a large vehicle weight, while the motor can reverse drag.
As we said above, the “reverse drag” of the motor achieves the effect of vehicle deceleration. When the kinetic energy recovery is strong, the vehicle decelerates significantly and the sliding distance is small. At this time, the kinetic energy recovery effect is the strongest; on the contrary, the vehicle has a long sliding distance and weak kinetic energy recovery effect. . By adjusting the current of the energized coil of the motor, the back-drag force of the motor is also adjusted, thereby realizing the grading of the kinetic energy recovery force.
Generally speaking, the recovery of kinetic energy will greatly improve the endurance performance of the vehicle, but if you consider it more “realistically”, it may not be necessary. After all, the kinetic energy recovery efficiency cannot reach 100%, which means that if frequent “kinetic energy recovery + start again”, the vehicle will waste more energy. Although this can hardly be accurately demonstrated by actual tests, it is theoretically true. Right?
Based on the above conclusions, for drivers of average driving level, more high-intensity kinetic energy recovery can be used on congested roads, because braking and starting under congested conditions may be easier to judge, and we may be able to use more low-level kinetic energy in unobstructed roads. Intensity kinetic energy recovery, because in this working condition, generally only need to decelerate, and does not require large speed changes or even brakes.
Of course, the above statement is also based on theory. In daily use cars, we don't need to be too entangled. In more cases, we can adjust the kinetic energy recovery according to our driving habits. Moreover, in the adjustment of the vehicle, there is usually a smarter cooperation between the kinetic energy recovery system and the mechanical braking system. For example, the driver does not need to brake vigorously. At this time, only the kinetic energy recovery may be involved. When the braking force required by the vehicle is more When full, the kinetic energy is recovered at full load, and mechanical braking will intervene. This is why the power of kinetic energy recovery reaches its peak when the brake pedal of many models is depressed.
Even for pure electric car users, I believe that many people are not accustomed to the driving feeling brought by kinetic energy recovery, because the kinetic energy recovery intervention process of some models is not smooth, and the braking force generated is a bit confusing. I personally think that for drivers who like to use this function, the relaxed driving experience it brings is a factor that cannot be ignored.
If you have never been exposed to kinetic energy recovery, I suggest you try more kinetic energy recovery modes with low or medium strength, and gradually adapt to the feeling of using less mechanical brakes. When you think “this thing does save your right foot” again Advanced to high-intensity kinetic energy recovery, maybe you will fall in love with this feeling. Of course, this is for models with better kinetic energy recovery adjustments. If the system is abruptly involved, the strength is not linear, and the logic is chaotic, then it really won’t make you like it. We can use “kinetic energy recovery” when choosing a car. Also try it as a reference item.
to sum up:
I believe that even if the battery life level of pure electric vehicles is constantly improving, manufacturers will still not give up the development of kinetic energy recovery systems, because the lost energy should not be used for nothing. Only after tuning can attract users, on the contrary, users can only get farther and farther away from it. In short, in terms of driving ease and endurance, I personally recommend that you try more kinetic energy recovery, maybe this can become your favorite.