Lithium battery charge and discharge balance -Lithium - Ion Battery Equipment

Lithium battery charge and discharge balance integration -Lithium - Ion Battery Equipment

With the development of battery technology, lithium-ion power lithium batteries have become an ideal power source for a new generation of electric vehicles due to their high energy density, good power characteristics, and long life. In order to meet the energy and power requirements of electric vehicles, power lithium battery packs are often formed by single cells in series and parallel for vehicles. Due to the inconsistency of battery performance, the performance of grouped batteries is far less than that of single batteries in terms of utilization, service life, and safety. The battery management system with efficient balanced management function can greatly improve the overall performance of the power lithium battery pack, effectively prolong the service life of the battery pack, and greatly reduce the use and maintenance costs of the entire vehicle. Provide technical support for the promotion of safe, efficient and practical electric vehicles.

At present, the battery management system has made some progress in battery online monitoring, state evaluation, charging management, data communication, control strategy, etc., but the research on high-efficiency balancing technology of battery packs is still in its infancy. The research of equalization technology is divided into two aspects: equalization control strategy, topology design of equalization circuit and hardware implementation. The practical application of online equalization strategy takes the external voltage of the battery as the control object. Since the external voltage cannot effectively reflect the actual internal difference of the battery, the equalization efficiency and effect are not ideal; in terms of hardware, the resistance bypass discharge equalization is mainly used, and the equalizing current is affected by It is difficult to increase the calorific value.(Lithium - Ion Battery Equipment)

Battery pack consistency and equalization strategy

The consistency of the battery pack refers to the differences in capacity, internal resistance, SOC, etc. between the single cells connected in series in the battery pack, which directly determines the performance of the entire battery pack, thereby affecting the power of electric vehicles. and cruising range. The important reasons for the inconsistency of batteries include: inconsistencies in the production process, differences in battery production processes and materials, resulting in differences between batteries in terms of initial capacity, DC internal resistance, self-discharge phenomenon, and charge-discharge efficiency. Differences in performance parameters accumulate during use; the consistency of initial battery performance parameters is amplified during use; differences in battery use environments have a greater impact on the consistency of battery packs.

Since the inconsistency of the battery comes from the internal resistance, capacity and SOC of the battery, and the voltage consistency other than the traditional consistency evaluation method and the equalization method is used as the control target, it does not effectively improve the usable capacity of the battery pack, so it cannot improve the consistency of the battery pack. The adverse effect of the sexual problem on the use of the battery pack.

Since the DC internal resistance, polarization voltage, and maximum usable capacity are specific parameters of the battery, they basically do not change during one or continuous charging and discharging processes. Therefore, the balance of the battery pack is mainly achieved by adjusting the SOC of each single cell. . After research, the SOC is taken as the reference object of the balance, the balance object is relatively fixed, the balance time is fully utilized, and the balance utilization rate is improved to reduce the balance current capacity.

Figure 1 Balance strategy software process

Taking the SOC of the battery as the control object, the SOC difference between the batteries is narrowed by charging and discharging the single battery. The first step is to determine the balancing target. Usually, in order to improve the efficiency of balancing and give full play to the advantages of charge-discharge balancing, the target is set as the average state of charge (SOC) of the battery pack. The balance control band (dSOC) is also set to prevent the fluctuation of the balance, and the cells with high SOC are discharged and balanced, and vice versa. 



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