The electric energy supplement of a pure electric vehicle can be divided into two modes, a charging mode and a power switching mode. The power exchange is also called mechanical charging, which is to achieve the purpose of electric vehicle electric energy supplement by directly replacing the charged power battery.
After the pure electric vehicle power battery is discharged, the DC power supply is used to connect the power battery, and the electric energy is converted into the chemical energy of the power battery to restore the working capacity. This process is called power battery charging. When the power battery is charged, the positive pole of the power battery is connected to the positive pole of the charging power source, and the negative pole of the power battery is connected to the negative pole of the charging power source, and the charging power source voltage must be higher than the total electromotive force of the power battery.
A suitable charging method not only maximizes the capacity of the battery, but also extends the life of the battery. Charging methods for pure electric vehicles include conventional charging methods and fast charging methods.
Conventional charging methods include constant current charging method, constant voltage charging method and stage charging method. The conventional charging method charges the electric vehicle with a lower charging current, and the charging time is generally longer, up to 10~20h; the charging cost of the conventional charging method is relatively low, the electric vehicle home charging facility (car charger) and the automobile This charging method is often used in charging stations. The charging period can fully utilize the power low period to charge, reduce the charging cost, improve the charging efficiency, and prolong the service life of the battery.
The fast charging methods include pulse charging method, variable current intermittent charging method, variable voltage intermittent charging method, etc. Here, common and basic charging methods are introduced. The fast charging method charges the battery in a short time with a higher charging current, and the charging time is short, which can be completed in 10-30 minutes. The charging method of the charging method is relatively high, the charging efficiency is low, and the battery life is also certain. Impact.
(1) Constant voltage charging method
Constant voltage charging is the most basic control method. The relationship between battery terminal voltage and current is shown in Figure 1. At the beginning, given a desired voltage value, the system begins to charge, and the charging current decreases continuously with charging; when the charging current is less than a certain value, the charging process ends. The biggest characteristic of constant voltage charging is that the control is simple. Since only a small current flows through the end of charging, the gassing amount is small and the energy consumption is low. However, since the charging current is too large at the initial stage of charging, it is easy to cause impact on the battery plate. The battery will be damaged; the constant voltage charging method is generally used for recharging the battery in the middle of the battery. At the beginning of the charging phase, it is necessary to add protective measures to limit the maximum current.
Figure 1 Constant voltage charging method
Figure 2 Constant current charging method
(2) Constant current charging method
The control process of the constant current charging method is shown in Figure 2. At the beginning, the charger charges the battery with a constant large current. When the battery is about to be fully charged, the battery is charged with a constant small current to enter the floating charge phase. The function of the floating charge is to compensate for the self-discharge of the battery. This method can completely charge the backward battery in the battery pack and eliminate the imbalance of the battery voltage; however, this method has a long charging time, serious gassing, and high energy consumption; the constant current charging method is a widely used charging method. method.
(3) Stage charging method
Commonly used phased charging methods are a two-stage charging method and a three-stage charging method. The control process of the two-stage charging method is shown in Fig. 3, and the control process of the three-stage charging method is as shown in Fig. 4. The two-stage method uses a combination of a constant current method and a constant voltage method, first charging with a constant current to a predetermined voltage value, and then changing to a constant voltage method to complete the remaining charging. The switching voltage between the two phases is generally the constant voltage held in the second phase.
Figure 3 Two-stage charging method
Figure 4 three-stage charging method
The three-stage charging method uses constant current charging at the beginning and end of charging, and charging with a constant voltage in the middle. The two-stage charging method first charges to a predetermined voltage value with a constant current, and then changes to a constant voltage. The switching voltage between the first two stages is generally also a constant voltage maintained in the second stage. When the current decays to a predetermined value, The two-stage conversion to the third stage performs constant current charging, and the switching current between the latter two stages is generally the constant current maintained in the third stage. This method can minimize the amount of gas.
(4) Pulse charging method
The pulse charging method first charges the power battery with a pulse current, then stops the battery for a period of time, and so on, as shown in FIG. The pulse charging method follows the inherent charging acceptance rate of the power battery, and can improve the power battery charging acceptance rate, thereby breaking the limitation of the power battery charging acceptance curve.
As shown in FIG. 5, the charging pulse fully charges the power battery, and the intermittent period causes the oxygen and hydrogen generated by the chemical reaction of the battery to be recombined and absorbed, so that the concentration polarization and the ohmic polarization are naturally eliminated. The internal pressure of the power battery is reduced, so that the next round of constant current charging can be performed more smoothly, so that the power battery can absorb more power. The charging method increases the discharge capacity, reduces the battery heating, improves the charging efficiency, shortens the charging time, does not generate a large amount of gas and heat, but the charging energy conversion efficiency is low, and the damage to the power battery is large.
Figure 5 pulse charging method
Figure 6 Variable current intermittent charging method
(5) Variable current intermittent charging method
The variable current intermittent charging method is based on constant current charging and pulse charging, and is characterized in that the constant current charging phase in the pulse charging is changed to limit the charging voltage to change the charging current intermittent charging, and the charging process is as shown in FIG. 6 . In the early stage of charging, the method of variable current intermittent charging is adopted to ensure that the charging current is increased and most of the charging amount is obtained. Charging at a constant voltage is used later in the charging process until the battery returns to full charge. The variable current intermittent charging method absorbs the oxygen and hydrogen generated by the chemical reaction by the intermittent recharging, and the absorption and the ohmic polarization are naturally eliminated, thereby reducing the inside of the power storage battery. Pressing, the next round of constant current charging can be carried out more smoothly.
(6) Variable voltage intermittent charging method
The variable voltage intermittent charging method differs from the variable current intermittent charging method in that the first stage is not intermittent constant current charging. Instead, intermittent constant voltage charging, the charging process is shown in Figure 7. This method is more in line with the charging curve for optimal charging. In each constant voltage charging phase, due to the constant voltage charging, the charging current naturally decreases exponentially, which is consistent with the characteristic that the power battery current acceptability decreases gradually with the charging.
LED Troffer driver
Fahold, a 8 year old company brings light power to your life by illuminating your offices, factories, warehouses, shopping malls, airports, etc. with its high quality LED Troffer lighting products and solutions.With global manufacturing standards and various certifications including CE,TUV, UL and FCC, our lighting products are sold in domestic market and are exported to various international markets including US, UK, France, Germany, Australia, Africa, Korea etc. We offer a wide range of Lighting source for LED lighting solutions which includes LED TrofferLighting or System, , LED Lams, LED Panel etc. At the same time Maximize beauty of your workplace with our powerful driver to drive Warehouse Lighting, Workshop Lighting, Supermarket Lighting and Factory lighting solutions. We have skilled engineers to answer all your questions and enquiries and provide all-round solutions basis on your project(s) and provide technical supporting.
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Parameter:
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