Method and apparatus for computing lithium ion batteries residual electric energy

Abstract

The invention provides a computing method of surplus energy of a lithium-ion battery and a device thereof. The method makes use of the combination method of the open circuit voltage of a lithium-ion battery pack and electric energy integral to compute the energy of charge and discharge, and according to the size of the open circuit voltage and the charge and discharge current, the DC impedance of the lithium-ion is computed in real time, and then the parameters such as DC impedance, charge and discharge currents, and the like, are used for determining the corresponding open circuit voltage of the available surplus energy of the lithium-ion battery pack under present circumstances when the discharge reaches a final voltage; on the basis of the present open circuit voltage, the actual surplus energy of the lithium-ion battery pack is computed when the discharge reaches the final voltage at last, the battery surplus energy available is obtained by the largest surplus energy minus the surplus energy in discharge termination condition. The computing method of the invention is applicable to accurately estimating the surplus energy of the battery in various conditions and the usage characteristics of a power battery and has the advantages of high accuracy, comparatively high practicability and high popularization value.

Description

Technical field [0001] The invention relates to a method and device for calculating the remaining electric energy of a lithium-ion battery pack. Background technique [0002] In electric vehicles and other power battery applications, lithium-ion batteries have become the first choice for future power batteries due to their unparalleled superior performance. With the continuous deepening of research, the technology of electric vehicles powered by lithium-ion batteries has gradually matured. However, there are still many unresolved problems in the current use of lithium-ion batteries, which restricts the continued development of lithium-ion batteries as power batteries. The state of charge (SOC) of a power battery is one of the important parameters that characterizes the battery status. Accurate measurement of SOC is the guarantee of battery safety and optimal control of charge and discharge energy. [0003] It is a common misconception that reduced lithium-ion battery capac...

AI Technical Summary

Problems solved by technology

[0009] The application of the open circuit voltage method is greatly limited due to the following two reasons;

[0010] First, batteries generally have a self-recovery effect. After a long period of standing, the open circuit voltage can gradually stabilize. At this time, the open circuit voltage can accurately represent the SOC. The power battery needs to be started frequently, and the operating current changes greatly. Therefore, the open circuit voltage cannot be stabilized in a short time, and the SOC estimated by this method has a large error

[0011] Second, the battery generally has a voltage plateau phenomenon. During the plateau period, the SOC has a large difference, but the corresponding open circuit voltage is small. During this period, the SOC estimated by the voltage has a large error

[0015] 1. There is no distinction between the remaining capacity and the available remaining capacity. The available remaining capacity of the lithium-ion battery pack is very different under different temperatures, currents and internal resistances. Therefore, if the available remaining capacity of the battery pack is not distinguished, it will give the battery a Energy calculations bring large errors

[0016] 2. The charging and discharging power is calculated in ampere-hour (Ah), and the voltage of the battery pack is not constant during use, so the calculation unit of ampere-hour cannot accurately represent the conversion of battery energy

[0017] 3. The determination of battery discharge termination conditions only considers the limit of the minimum discharge voltage of the battery pack itself, and does not take into account the requirements of the load itself for voltage and power

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