CN-122026567-A - Passive equalization method and device for lithium battery pack

CN122026567ACN 122026567 ACN122026567 ACN 122026567ACN-122026567-A

Abstract

A passive equalization method and device for a lithium battery pack comprise the steps of judging whether the lithium battery pack is subjected to passive equalization according to whether working condition environments of the lithium battery pack meet set conditions or not, recognizing whether abnormal monomers exist in the lithium battery pack after the working condition environments are determined to meet the set conditions, executing a passive equalization process on normal battery monomers except the abnormal monomers in the lithium battery pack if the abnormal monomers exist, executing the passive equalization process on the normal battery monomers in the lithium battery pack if the abnormal monomers do not exist, and gradually adjusting the voltage of each normal battery monomer to an equalization state. The invention has ideal equalization effect, avoids excessive equalization and prolongs the service life of the lithium battery.

Inventors

LIN YIBIN
XU HONGRU
Zhu Jiaowei
TAO XIMENG
LIN SIXUE
MA RUIQUAN
WU SHIQING

Assignees

林德（中国）叉车有限公司

Dates

Publication Date: 20260512
Application Date: 20241105

Claims (10)

1. A passive equalization method of a lithium battery pack is characterized by comprising the steps of judging whether the lithium battery pack is subjected to passive equalization according to whether a working condition environment of the lithium battery pack meets a set condition or not, after the working condition environment is confirmed to meet the set condition, identifying whether abnormal monomers exist in the lithium battery pack, if the abnormal monomers exist, executing a passive equalization process on normal battery monomers except the abnormal monomers in the lithium battery pack, and if the abnormal monomers do not exist, executing the passive equalization process on the normal battery monomers in the lithium battery pack, and gradually adjusting the voltage of each normal battery monomer to an equalization state.
2. The method of claim 1, wherein the working condition environment includes working parameter information and environment information, the lithium battery pack does not perform passive equalization when the working parameter information or the environment information of the lithium battery pack does not meet a set condition, and the lithium battery pack performs passive equalization when the working parameter information and the environment information of the lithium battery pack meet the set condition.
3. The method of claim 2, wherein the operating parameter information includes a discharge state and a discharge current, and the operating environment of the lithium battery pack does not satisfy a set condition when the lithium battery pack is in the discharge state and the discharge current exceeds a first current threshold.
4. The method of claim 2, wherein the operating parameter information includes a stationary state and a current value, and the operating environment of the lithium battery pack does not satisfy a set condition when the lithium battery pack is in the stationary state and the current value is greater than a second current threshold.
5. The method of claim 2, wherein the environmental information includes temperature information or humidity information, and the lithium battery pack does not perform the passive equalization process when the temperature information of the lithium battery pack environment does not exceed a set temperature threshold or the humidity information does not exceed a set humidity threshold.
6. The method of claim 1, wherein the abnormal cells include aged cells, and wherein identifying whether aged cells are present in the lithium battery comprises: continuously monitoring and recording a battery cell with the lowest voltage value in the discharging process of the lithium battery pack, and if the lowest voltage value of the battery cell continuously exceeds a set first time length, determining the battery cell as the battery cell with the lowest voltage; after the lithium battery pack is fully charged, continuously monitoring and recording a battery cell with the highest voltage value, and if the highest voltage value of the battery cell continuously exceeds a set second time length, determining the battery cell as the battery cell with the highest voltage; And if the battery cell with the lowest voltage and the battery cell with the highest voltage are the same battery cell, the battery cell is considered as an aged battery cell.
7. The method of claim 1, wherein the abnormal cells include cells with poor contact, and identifying whether there is a cell with poor contact in the lithium battery comprises the steps of: And when the lithium battery pack is in a static state, judging whether the average voltage of the lithium battery pack is in a set voltage threshold range, if so, determining that the absolute value of the difference value between the voltage of the battery cells in the lithium battery pack and the average voltage is larger than a set first difference value threshold, and determining that the battery cells with the voltage duration time larger than a set third time length are poor-contact battery cells.
8. The method for passive equalization of a lithium battery pack according to claim 1, wherein a passive equalization process is performed on normal cells except for said abnormal cells in said lithium battery pack, and the voltage of each of said normal cells is adjusted stepwise to an equalization state, comprising the steps of: judging the voltage of the normal battery cell in the lithium battery pack, when the difference value between the highest voltage and the lowest voltage is larger than or equal to a set second difference value threshold value, starting equalization and continuously operating for a fourth time length, suspending a fifth time length, and repeating equalization until the difference value between the highest voltage and the lowest voltage is smaller than or equal to a set third difference value threshold value, wherein the third difference value threshold value is smaller than the second difference value threshold value.
9. The method for passive equalization of a lithium battery pack according to claim 1, wherein a passive equalization process is performed on normal cells except for said abnormal cells in said lithium battery pack, and the voltage of each of said normal cells is adjusted stepwise to an equalization state, comprising the steps of: Calculating the average voltage of the normal battery cells in the lithium battery pack, inquiring corresponding opening threshold values and closing threshold values from an equalization threshold value comparison table according to the average voltage, starting equalization if the voltage of a single normal battery cell reaches or exceeds the opening threshold value, and closing equalization if the voltage of each normal battery cell is lower than the closing threshold value; during the equalization, a cycle mode is employed in which the seventh time period is stopped after the sixth time period is run and the average voltage of the normal cells is periodically recalculated to query for new on and off thresholds.
10. A passive equalization device for a lithium battery pack, comprising: The judging module is used for judging whether the lithium battery pack performs passive equalization according to whether the working condition environment where the lithium battery pack is positioned meets the set condition; The abnormal monomer identification module is used for identifying abnormal monomers in the lithium battery pack after determining that the working condition environment meets the set condition; and the equalization module is used for executing a passive equalization process on the normal battery monomers except the abnormal monomers in the lithium battery pack, and gradually adjusting the voltage of each normal battery monomer to an equalization state.

Description

Passive equalization method and device for lithium battery pack Technical Field The invention relates to the field of lithium battery packs, in particular to a passive equalization method and device of a lithium battery pack. Background Lithium batteries are widely used as new energy sources. The passive equalization technology is widely adopted to equalize the single electric quantity by virtue of the advantages of simple circuit and easy realization, so that the performance and the safety of the battery pack are improved, the service life is prolonged, and the overall efficiency is enhanced. At present, a passive equalization technology is often used for improving the problem of inconsistent voltage of each single battery, and the strategy is mainly to consume high-voltage energy in a resistor discharge mode according to the voltage value of each single battery of a lithium battery pack, and finally, the electric quantity of each single battery of the lithium battery pack is basically consistent. In the prior art, one scheme is to automatically identify and moderately discharge a battery cell with a voltage higher than a preset voltage difference value in the tail sound stage of a charging period, so that voltage balance among monomers is ensured, the overall capacity of the lithium battery pack is further improved, and the service life of the lithium battery pack is prolonged. The method is only realized in a charging mode, and the method can be executed only when the lithium battery pack is in the charging mode and the charging time is longer than the preset time, so that the effect is limited for the lithium battery pack which is not charged frequently or is short of the charging time. In another scheme, when the lithium battery pack enters a charging end stage or a standing state, the voltage consistency of the single lithium batteries in the lithium battery pack is optimized through a specific balance control strategy, so that the overall performance and the service life of the lithium battery pack are improved. Although this solution proposes a specific equalization control strategy, it lacks a special case specific analysis solution, affecting the equalization effect. The other scheme is that the passive equalization of the lithium battery pack is realized by accurately estimating the capacity, the residual discharge capacity and the residual charge capacity of the lithium battery cells in the lithium battery pack and calculating the equalization capacity value based on the estimated values, so that the electric quantity among the lithium battery cells is consistent, and the overall performance and the capacity utilization rate of the lithium battery pack are improved. According to the scheme, the capacity, the residual discharge capacity and the residual charge capacity of each lithium battery monomer are required to be accurately estimated, the calculation process is relatively complex, and the calculation capability and the instantaneity of the system are required to be high. All three schemes are poor in consideration of practical use conditions of the lithium battery in the aspect of passive balance, and lack of protection of the lithium battery. In addition, the current passive equalization strategy aims at all lithium battery monomers, if the equalization strategy does not comprehensively consider some practical use conditions, some special abnormal monomers are protected, the service life of the lithium battery is influenced, and even the damage of the lithium battery is aggravated. Disclosure of Invention The invention mainly aims to overcome the defects of poor consideration of actual use conditions of a lithium battery and lack of protection of the lithium battery in the prior art, and provides a passive equalization method and device for a lithium battery pack, which effectively protect abnormal monomers, avoid excessive equalization, optimize policy logic in an equalization stage, have ideal equalization effect and greatly prolong the service life of the lithium battery. The invention adopts the following technical scheme: A passive equalization method of a lithium battery pack comprises the steps of judging whether the lithium battery pack is subjected to passive equalization according to whether working condition environments of the lithium battery pack meet set conditions or not, after the working condition environments are determined to meet the set conditions, identifying whether abnormal monomers exist in the lithium battery pack, executing a passive equalization process on normal battery monomers except the abnormal monomers in the lithium battery pack if the abnormal monomers exist, and executing the passive equalization process on the normal battery monomers in the lithium battery pack if the abnormal monomers do not exist, and gradually adjusting the voltage of each normal battery monomer to an equalization state. Further, the working condition environment comprises working p