Battery pack capacity balancing method
An equalization method and technology of battery packs, applied in charge equalization circuits, battery circuit devices, arrangement of multiple synchronous batteries, etc., can solve problems such as difficult and over-balanced battery packs, achieve durability and safety improvement, and solve Effect of Energy Density Decrease
Active Publication Date: 2021-08-31
UNIV OF SHANGHAI FOR SCI & TECH
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Problems solved by technology
The disadvantage of the voltage-based equalization algorithm and the state-of-charge-based equalization algorithm is that the goal is to have the same voltage or state of charge, and due to the lack of information on the capacity of the battery cell, it may lead to over-balance of the battery pack.
Of course, the difficulty based on capacity equalization lies in how to obtain the battery cell capacity and state of charge, which is extremely difficult for online calculation and identification
Method used
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Embodiment
[0023] This embodiment provides a method for equalizing the capacity of a battery pack, which uses equalizing resistors to perform capacity equalization on a battery pack including N battery cells, specifically including the following steps:
[0024] In this embodiment, the number of battery cells is four.
[0025] Step S1, setting a voltage threshold U of the battery cell during the charging process of the battery pack t .
[0026] In this embodiment, a lithium iron phosphate battery is used, and the voltage threshold setting standard is at the end of the charging voltage curve of the lithium iron phosphate battery, generally after the plateau period, where U t = 3.5V (volts).
[0027] Step S2, when the charging voltage U of the battery cell i greater than or equal to the voltage threshold U t , start to calculate the charging current integral of the battery cell, and end when the charging ends or the smallest battery cell reaches this threshold. At this time, each batter...
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The invention provides a battery pack capacity balancing method. The battery pack capacity balancing method comprises the following steps: setting a voltage threshold Ut of a battery monomer in a charging process of a battery pack; when the charging voltage Ui of each single battery is greater than or equal to a voltage threshold value Ut, starting to calculate the charging current integral of the single battery until the charging is finished or the minimum single battery reaches the threshold value, wherein at the moment, each single battery has a corresponding charging current integral Qe, i; taking a charging current integration result as a target balanced discharging electric quantity QE, i; calculating the discharge equalization electric quantity of the equalization resistor in each time delta t period, and recording the discharge equalization electric quantity as IE * delta(t); continuously subtracting the target equalization discharge electric quantity from the discharge equalization electric quantity of the equalization resistor in each time delta(t) period to obtain difference values QE and i_j + 1, and then carrying out iteration on the difference values QE and i_j + 1; when the difference values are greater than a set value Qd, switching on an equalization resistor switch and starting equalization of the battery pack, and when the difference values are smaller than or equal to the set value Qd, switching off the equalization resistor switch and ending equalization of the battery pack.
Description
technical field [0001] The invention belongs to the technical field of power batteries, and in particular relates to a battery pack capacity equalization method. Background technique [0002] In the functional system of pure electric vehicles, due to the limitation of the voltage and capacity of single lithium batteries, hundreds of battery cells must be connected in series and parallel to form a battery pack to provide sufficient power and energy for pure electric vehicles to meet their acceleration and climbing. and mileage requirements. If there is no difference between battery cells, then the battery pack and battery cells of a pure electric vehicle are consistent in terms of service life and safety. However, there are always inconsistencies between battery cells due to inconsistencies in the manufacturing process and inconsistencies in the environment during use. After the battery cells are grouped, their energy density, durability, and safety performance will all dec...
Claims
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IPC IPC(8): H02J7/00
CPCH02J7/0014H02J7/0029H02J7/0048H02J7/007Y02T10/70
Inventor 郑岳久钱广俊陈英杰王万泉孙跃东徐雨文
Owner UNIV OF SHANGHAI FOR SCI & TECH