lithium 3400mah 3.7v 18650 battery.Integrated battery management system solution for lithium battery charge and discharge balancing

　　At present, battery management systems have made certain progress in battery online monitoring, status assessment, charging management, data communication, control strategies, etc., but research on battery pack efficient balancing technology is still in its infancy. The research on equalization technology is divided into two aspects: equalization control strategy and equalization circuit topology design and hardware implementation.

　　With the development of battery technology, lithium-ion power batteries have become the ideal power source for the 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, single cells are often connected in series and parallel to form a power battery pack for vehicle use. Due to the problem of inconsistent battery performance, the performance of battery packs in terms of utilization, service life, safety, etc. is far inferior to that of single batteries. A battery management system with efficient balancing management function can greatly improve the overall performance of the power battery pack, effectively extend 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, battery management systems have made certain progress in battery online monitoring, status assessment, charging management, data communication, control strategies, etc., but research on battery pack efficient balancing technology is still in its infancy. The research on equalization technology is divided into two aspects: equalization control strategy and equalization circuit topology design and hardware implementation. The practical online balancing strategy uses the external voltage of the battery as the control object. Since the external voltage cannot effectively reflect the actual internal differences of the battery, the balancing efficiency and effect are not ideal. In terms of hardware, resistor bypass discharge balancing is mainly used, and the balancing current is affected by It is difficult to increase the heat output due to the limitation of caloric value.

　　Battery pack consistency and balancing strategy

　　The consistency problem 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 the electric vehicle. and cruising range. The main reasons for battery inconsistency include: inconsistencies in the production process, differences in battery production processes and materials, resulting in differences in initial capacity, DC internal resistance, self-discharge phenomena and charge and discharge efficiency between batteries; battery initialization Differences in performance parameters accumulate during use; the consistency problem of the battery's initial performance parameters is amplified during use; differences in battery usage environments have a greater impact on battery pack consistency issues.

　　Since the inconsistency of the battery comes from the internal resistance, capacity and SOC of the battery, and the traditional consistency evaluation method and equalization method use voltage consistency as the control target, it does not effectively increase the available capacity of the battery pack, so it cannot improve the consistency of the battery pack. The adverse effects of sexual problems on the use of battery packs.

　　Since the DC internal resistance, polarization voltage, and maximum available capacity are specific parameters of the battery and basically do not change during one or several consecutive charge and discharge processes, the balance of the battery pack is mainly achieved by adjusting the SOC of each single cell. . After research, SOC is used as the reference object for balancing. The balancing object is relatively fixed. Make full use of the balancing time and improve the balancing utilization rate to reduce the balancing current capacity.

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