Lithium ion power battery self-discharge consistency evaluation method

Abstract

A lithium ion power battery self-discharge consistency evaluation method comprises the following steps: 1, selecting a plurality of batteries with good capacitance and internal resistance consistencyfrom lithium iron phosphate batteries of the same production batch, the same specification model and the same material system; using a constant current constant voltage charging system and a constantcurrent discharge system to charge and discharge the batteries for many times in cycle under the room temperature; 2, adjusting the batteries to an empty charge state under the room temperature; 3, screening batteries with the self discharging rate bigger than 3%; 4, adjusting the battery SOC to 10%SOC to 30% SOC charge state; 5, measuring the open-circuit voltage after battery high temperature laying, and calculating the battery voltage drop [delta]V or voltage drop K in a unit time; 6, calculating the average value X of all battery [delta]V or K values and the standard deviation [sigma], andselecting the batteries in the confidence interval of [X-2[sigma], X+2[sigma]]. The method can improve the battery self discharging rate, can shorten the laid-up period, and can reduce the productioncost.

Description

technical field [0001] The present application relates to the field of power batteries, in particular to a method for evaluating the self-discharge consistency of lithium-ion power batteries. Background technique [0002] As the core energy component of electric vehicles, the development of power batteries has become a key factor in the development of electric vehicles, and lithium iron phosphate power batteries occupy the leading position in electric vehicles due to their superior safety performance, long cycle life and stable voltage platform. The main market for power batteries. However, under the current level of power battery technology, electric vehicles must use a battery pack composed of multiple single cells to meet the requirements of use, which puts forward high requirements on the consistency of lithium iron phosphate power batteries. [0003] At present, lithium iron phosphate power batteries need to be screened for performance consistency of single batteries b...

AI Technical Summary

Problems solved by technology

This method requires more manpower and electricity, which not only increases the production cost, but also prolongs the production cycle.

Moreover, most of this method adopts the self-discharge screening of lithium iron phosphate batteries in the discharge state. However, due to the polarization of the battery, the voltage rebounds after the battery is discharged, and the degree and rate of voltage rebound between different batteries are different, resulting in The voltage consistency of the battery discharge state before shelving is very poor, and the voltage after shelving is even greater than the voltage before shelving, that is, the voltage difference is negative, so this method of using the discharge state voltage difference to screen the consistency of the battery There are certain disadvantages; another method is the barcode management method, which achieves the consistency of self-discharge of battery packs through automated production lines. This method is difficult to implement in China within a short period of time