Manufacturers analyze commonly used voltage equalization circuits used in series with lithium batteries

Manufacturers analyze the voltage equalization circuit commonly used in series with lithium batteries. Because of the particularity of lithium batteries, lithium battery packs are usually equipped with protection circuits for common use. With the development of the lithium battery industry, the energy density of lithium batteries is getting higher and higher. Power lithium batteries are more inclined to use high energy density lithium batteries, and a voltage equalization circuit must be used in the series use of power lithium batteries. Lithium battery manufacturers will share with you, several battery equalization circuits that are often used, and I hope it will be helpful to everyone. 1. Load consumption balance mode That is, a resistor is connected in parallel to each battery, and a switch is connected in series for control. When the voltage of a string of batteries is too high, the switch is passively turned on, and the charging current is shunted through the resistor. In this way, the charging current of a high-voltage battery is smaller, and the charging current of a low-voltage battery is larger. In this way, the voltage balance of the power battery pack can be achieved. However, this method is only suitable for low-capacity batteries. The higher the capacity, the greater the current that needs to be balanced, the more difficult the balancing of this method will be. Load consumption balance principle diagram 2. Swing capacitance method Each battery is connected in parallel with a capacitor, and the capacitor can be connected in parallel with the switch. When the voltage of a string of cells is too high, first connect the capacitor to the battery in parallel, and the capacitor voltage is the same as the battery voltage. The capacitor is then switched to the adjacent battery, and the capacitor discharges the battery. Realize the transfer of energy. Since the capacitor does not consume energy, it can achieve a lossless energy transfer. If it is this way, a lot of switches are needed to control it. The working principle diagram of the Fit Capacitor Method is to draw the principle diagram of the equilibrium of two adjacent batteries. The first equilibrium is the charging of the power battery pack. The 80AH battery capacity is connected in parallel with the two groups, and the equilibrium current requirement is 10A. The principle of the original balance is not enough in theory. Such a large current is equivalent to a small module. In the end, it is really a small module of the n series. Each battery is connected in parallel with a small module. If the voltage of the single battery is lower than the setting Value, start the corresponding modules in parallel, start charging the low-voltage battery, replenish energy, increase the voltage, and achieve balance. The figure below is the schematic diagram of the equalizing circuit used at that time. The DC-DC input bus can be battery voltage or DC input provided by other modules, which can be flexibly configured as required. The active equalization method can use the aforementioned transformer multiplexing method. I used this balance method to balance 1000AH, 7 series batteries and 300AH, 80 series batteries. After the balance is completed, the voltage of all single cells can reach within 5mV. Active equalization of the structure diagram of the multi-winding transformer method can also take the form of energy transfer. The so-called energy transfer can obtain energy from the entire set of voltages to supplement the low-voltage part, or obtain energy from the over-voltage battery to feed back the entire set of voltages. The second method realizes battery balancing in the communication power supply system. The schematic diagram of the circuit is as follows: So what we have done is to balance 16 lithium batteries and divide them into two groups with 8 batteries in each group. Here we only draw 6 to describe how they work. During the experiment, the two groups were balanced. When there are deviations between the two groups, bidirectional DC-DC can be used for energy conversion, the number of modules used is small, and the design is more convenient. Here does not use bidirectional DC-DC, but simply uses energy consumption to balance the batteries between the two groups. From the final test results, the balance of the battery is relatively good. If the voltage of battery B5 is too high, control Q5 to work in PWM mode. When Q5 is turned on, the inductor L5 can store energy. When Q5 is turned off, the energy stored in the inductor charges the batteries B1-B4 through D5, reducing the voltage of the B5 battery and increasing the voltage of the remaining batteries. The same principle can also be used to analyze the working process of the remaining battery pack when the voltage is too high. In the process of balancing, if you feel that it is not necessary to provide all the charging modules for each battery, the energy consumption does not meet the technical requirements, and active balancing is required. Then the above-mentioned transformer one-to-multiple output method may be more suitable and suitable for use. The transformer can be used as a current-limiting multi-output flyback power supply with primary side feedback. With the development of power lithium battery applications, not only the battery balance, overcharge and overdischarge protection needs to be appropriate, but also that the application of plate protection will become more and more extensive. Disclaimer: The articles published on this site are all from the Internet and do not represent the views of this site. If there is any infringement, please contact to delete WeChat: Disclaimer: Some pictures and content of the articles published on this site are from the Internet. 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