Voltage equalization circuit for multiple serially connected batteries

Abstract

The invention discloses a voltage equalization circuit for multiple batteries connected in series, and belongs to the technical field of equalization of lithium ion batteries. A power supply negative terminal IN-; the power supply anode end IN + is connected with the input end of the constant-current discharge loop; the output end of the constant-current discharge loop is connected with the input end of the switch K1, and the output end of the switch K1 is connected with the negative end IN-of the power supply; the resistor R4 is used as a current-limiting resistor, the positive terminal IN + of the power supply is connected with the resistor R4, and the resistor R4 is connected with the constant-current discharge loop in parallel; and a triode V1. The battery equalization circuit is composed of the high-precision three-end precision voltage-regulator tube, the resistor and the constant-current discharge loop, the equalization current is kept unchanged no matter how high the battery voltage is, the large equalization current can be achieved, the equalization control voltage precision is very high, the voltage difference value between the single batteries is very small and the state of charge is consistent when equalization is completed, and the battery equalization circuit is suitable for large-scale popularization and application. Therefore, the overall service life of the battery pack is prolonged.

Description

technical field [0001] The invention relates to the technical field of equalization of lithium-ion batteries, and more specifically relates to a voltage equalization circuit of multiple series-connected batteries. Background technique [0002] With the rapid development of the battery industry, there are more and more applications of multi-cell batteries in series, such as electric bicycles, electric vehicles, energy storage systems, communication backup battery packs and other fields. When the battery is used in series, due to the inconsistency of the battery, the state of charge of the battery pack will be inconsistent and out of balance, which will cause some internal cells to be overcharged when the battery pack is charging, and the Some battery cells are not fully charged; when the battery pack is discharged, the battery cells that are not fully charged are prone to over-discharge, resulting in increased life attenuation or safety problems, which greatly shortens the ov...

AI Technical Summary

Problems solved by technology

[0003] Among the existing equalization methods, active equalization has the advantage of high energy utilization, but the circuit is complicated, the reliability is poor and the cost is high, so it is rarely used in the market

The disadvantage of the overvoltage equalization method in passive equalization is that the equalization current is small and the equalization is turned on when it is close to the end of charging, so the equalization time is short and the equalization efficiency is low; while the overvoltage equalization uses a dedicated chip. The voltage accuracy is only about 20mV, so the voltage difference between the single cells will be large when the equalization is completed; and when the charging voltage is lower than the normal voltage, the overvoltage equalization method will not work, for example, for a battery pack of 10 series , the normal charging voltage is 42V, if the output voltage of the charger is 0.5% lower, it is 41.79V, when the voltage of 9 batteries is 4.2V, and the voltage of 1 battery is 3.99V, this kind of equalization circuit will not work, and it will not be able to charge the battery. Perform equalization; for the charging equalization method in passive equalization, the single battery with higher voltage is discharged through the resistance during the charging process, which requires the BMS of the battery pack to detect the voltage of the single battery with higher accuracy, but the current market The voltage detection accuracy of the front-end analog voltage acquisition chip on the Internet is generally only 20mV, and a few high-precision ones can only achieve about 10mV, and if it is a lithium iron phosphate battery, in the middle voltage region, there will be a voltage difference of 1mV. 1.5% difference in charging capacity, low voltage detection accuracy will lead to poor charging equalization effect, and it is even more likely that the battery pack will aggravate the unbalanced state due to large voltage detection error, and due to the charging equalization on the market It is a way to discharge the battery through the resistance. When the battery voltage is low, the equalization current is small, which affects the equalization efficiency.

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