Method for estimating state of charge of soft package lithium-ion battery

Abstract

The invention relates to a method for estimating the state of charge of a soft package lithium-ion battery. The method comprises a step S1 of acquiring battery surface dynamic stress and a battery working state signal that includes first data for indicating that a battery is in a charging, standing or discharged state; a step S2 of determining whether the battery is in a standing state, if so, executing a step S3, and otherwise, executing a step S4; the step S3 of taking the previous estimation result as the current state of charge of the lithium-ion battery; the step S4 of obtaining battery surface static stress according to the battery surface dynamic stress, and executing a step S5; and the step S5 of estimating the state of charge of the lithium-ion battery by combining a corresponding function of the static stress and the state of charge according to the obtained battery surface static stress. Compared with the prior art, the invention achieves the estimation of the charge of charge of the lithium-ion battery by using a method based on stress measurement, and reduces the system complexity while improving the system accuracy.

Description

technical field [0001] The invention relates to a method for estimating the state of charge of a lithium-ion battery, in particular to a method for estimating the state of charge of a soft-pack lithium-ion battery. Background technique [0002] When the traditional battery management system (Battery Management System, BMS) estimates the internal state of the battery, especially the SOC, it is basically based on the open circuit voltage OCV of the lithium-ion battery or the battery equivalent circuit method. In fact, this method has a Congenital disadvantages, that is, the estimation of the voltage plateau area is inaccurate, especially for lithium iron phosphate batteries; at present, some new methods, such as fuzzy logic, artificial neural network and support vector machine, are gradually applied to the estimation of SOC, but the above The method requires a large amount of data support, and the model is complex. [0003] To sum up, the battery SOC estimation methods curren...

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Problems solved by technology

[0004] After 2000, research on the stress of lithium-ion batteries has gradually attracted people's attention. The inventors found that the surface stress of lithium-ion batteries is mainly related to lithium intercalation in electrodes, and the degree of lithium intercalation in electrodes can represent the state of charge of the battery. After in-depth experimental measurements and theoretical Analysis, the inventors found that there is a one-to-one relationship between the surface stress and SOC of the soft-pack lithium-ion battery, and the curve is monotonic, the charge and discharge hysteresis is not obvious, and the charge and discharge stress curves in the platform area basically coincide. If this discovery is applied In the estimation of the state of charge of lithium-ion batteries, it can solve the disadvantages of inaccurate estimation of the plateau area by methods such as equivalent circuits

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