Battery equalization evaluation method for new energy battery charging

Abstract

The invention relates to a battery equalization evaluation method for new energy battery charging, which comprises the following steps: acquiring SOC-battery cell charging voltage curve characteristics in a single battery cell charging process, selecting an interval needing equalization, and recording the voltage of the interval as [V1, V2] and the SOC as [SOC1, SOC2]; presetting a threshold value V3 of the voltage difference of the single battery cells; collecting the voltage V of each single battery cell in real time to form a battery system voltage set, and determining the highest voltage Vmax of the single battery cells in the battery system; judging whether the highest voltage Vmax of the single cells is greater than V1 and smaller than V2 or not, if so, entering the next step, calculating the difference value between the voltage V of each single cell and MAX (V1, Vmin), comparing the difference value with a preset threshold value V3 of the voltage difference of the single cells, and outputting balance evaluation information of the single cells; and starting equalization according to the equalization evaluation information of the single battery cells. The whole vehicle working condition constraint conditions are few, and the equalization time can be calculated as long as it is judged that the voltage difference of the single bodies exceeds the threshold value in the charging process.

Description

technical field [0001] The invention belongs to the field of new energy vehicle batteries, in particular to the field of battery balance evaluation methods. Background technique [0002] With the increasingly stringent energy conservation and emission reduction, new energy vehicles have ushered in rapid development. Lithium batteries have become the core components of new energy vehicles because of their high energy density and become the power heart of new energy vehicles. The cell voltage of the lithium battery is relatively low. When loaded into the electric vehicle, a high-voltage battery system is formed by connecting several lithium batteries in series to provide power for the motor; due to the limitation of the technical level of the cell, it is difficult to achieve 100% of the cell Consistency, although in the process of forming a battery system, cells with similar capacity, internal resistance, and self-discharge rate are usually used to form a group, but due to dif...

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Problems solved by technology

The cell voltage of the lithium battery is relatively low. When loaded into the electric vehicle, a high-voltage battery system is formed by connecting several lithium batteries in series to provide power for the motor; due to the limitation of the technical level of the cell, it is difficult to achieve 100% of the cell Consistency, although in the process of forming a battery system, cells with similar capacity, internal resistance, and self-discharge rate are usually used to form a group, but due to differences in structure and process, even if the self-discharge rate of a lithium battery cell is only 1% to 2%, the small self-discharge rate difference between lithium battery cells has been accumulated for a long time, causing the entire battery system to reduce the overall capacity of the battery system due to the short board effect, thereby causing the attenuation of the cruising range of the car; at present, The main equalization method is to use the dynamic voltage difference of the battery cells to balance the cells with high battery voltage during the charging process, and consume the excess power with the equalization resistance through heating. By reducing the difference in battery voltage, this method has obvious disadvantages. First, the equalization can only be turned on during the charging process, resulting in a short equalization time and low efficiency; second, for lithium iron phosphate batteries, only at the end of charging There is an obvious battery voltage difference between the battery and the discharge end, resulting in complex equalization conditions and lower equalization efficiency

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