JP4902066B2 - Battery pack system and battery pack deterioration determination method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technology for determining battery deterioration of a battery pack that is mounted on an electric vehicle, a hybrid vehicle, or the like and that includes an assembled battery in which a plurality of unit cells that are alkaline secondary batteries such as nickel-hydrogen batteries are connected.
[0002]
[Prior art]
Recently, in an electric vehicle (PEV) and a so-called hybrid vehicle (HEV) equipped with an engine and a motor, as a main power source for driving the motor, its high energy density (that is, energy can be stored compactly) and high In view of power density, nickel-hydrogen (Ni-MH) batteries are mainly used. In such PEV and HEV, a plurality of unit cells are combined into one assembled battery so that a sufficient output can be supplied to the motor, and the assembled battery is built in the battery pack together with the battery control unit and the like.
[0003]
When such a battery pack for PEV or the like is used by configuring a battery pack by connecting a large number of battery cells in series, the characteristics of the battery cells are basically the same. It is designed so that performance can be fully demonstrated.
[0004]
[Problems to be solved by the invention]
However, it is actually impossible to manufacture the assembled battery so that the characteristics of the single cells are all the same. For this reason, for example, in JP-A-1-134877, a lead-acid battery is provided with one long-life cell and several normal cells, and the voltage difference between the long-life cell and the normal cell is constantly monitored. A configuration is disclosed in which a life deterioration warning is issued when the difference exceeds a certain value.
[0005]
Such a conventional lead-acid battery is mainly intended for starting the engine, and, for example, in order to obtain a voltage of 12V, only six 2V single cells are connected in series. On the other hand, when an assembled battery is configured by connecting a large number of single cells in series like a battery pack for PEV or the like, in order to perform battery deterioration determination safely and reliably, the single cell Although it is necessary to monitor the state of each battery, there are problems that the number of single cells is so large that it is difficult to manufacture and the cost increases.
[0006]
On the other hand, if the battery pack charge / discharge control is performed by detecting the voltage etc. in units of blocks that can control the battery within a range that does not cause a serious malfunction, the battery status of each unit cell cannot be recognized, and the life It is difficult to ascertain when and where the battery reaches, as well as signs of deterioration. Therefore, since the index and reference | standard of replacement | exchange time of a battery pack are not clear, when using a battery as a motive power source like PEV and HEV, there existed a problem that a vehicle running performance might be affected.
[0007]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a battery pack system for an electric vehicle or the like capable of safely and reliably performing end-of-life determination at low cost and battery pack deterioration determination. It is to provide a method.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a battery pack system according to the present invention is a battery pack system having an assembled battery in which a plurality of single cells as secondary batteries are connected, and the assembled battery is charged and discharged. As a result, the internal resistance is always increased faster than other unit cells, and a unit cell for comparison and determination that always begins to deteriorate is provided.
[0009]
In this battery pack system, a current detection unit that detects a current flowing through the assembled battery, a first voltage detection unit that detects a voltage of the comparison determination unit cell, and a first unit that detects a voltage of another unit cell in block units. 1st internal resistance which calculates the 1st internal resistance of the cell for comparison judgment based on the voltage data of 2 voltage detection parts, the current data from at least the current detection part, and the voltage data from the 1st voltage detection part A second internal resistance calculation unit that calculates a second internal resistance of another unit cell based on at least the current data from the current detection unit and the voltage data from the second voltage detection unit; It is preferable to include a deterioration determination unit that performs battery deterioration determination based on the first internal resistance and the second internal resistance.
[0010]
In this case, it is preferable that the comparative determination unit cell has a separator having a larger weight per unit area than other unit cells.
[0011]
Alternatively, it is preferable that the comparative determination unit cell is configured to have a smaller amount of electrolytic solution than other unit cells.
[0012]
The secondary battery is preferably a nickel / hydrogen secondary battery.
[0013]
In order to achieve the above object, a battery pack deterioration determination method according to the present invention is a method for determining deterioration of a battery pack having an assembled battery in which a plurality of single cells as secondary batteries are connected. As the battery is charged / discharged , the internal resistance always rises faster than the other cells, and the battery for comparison judgment is always arranged, which first starts to deteriorate . Comparing the internal resistance of one cell in units of cells, the step of monitoring the second internal resistance of another unit cell in units of blocks, and comparing the first internal resistance and the second internal resistance, The battery deterioration determination is performed.
[0014]
In this case, it is preferable that the comparative determination unit cell has a separator having a larger weight per unit area than other unit cells.
[0015]
Alternatively, it is preferable that the comparative determination unit cell is configured to have a smaller amount of electrolytic solution than other unit cells.
[0016]
The secondary battery is preferably a nickel / hydrogen secondary battery.
[0017]
According to the above-described configuration, the battery pack constituting the battery pack is provided with the comparative determination unit cell in which the internal resistance always rises faster than other unit cells and always starts to deteriorate first. The internal resistance of the battery is monitored in units of cells, and for other single cells, the internal resistance is monitored in units of blocks in which voltage etc. are detected, and both internal resistances are compared to ensure safety, reliability, and low The end of battery life can be determined at a low cost.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
[0019]
FIG. 1 is a block diagram showing a configuration of a battery pack according to an embodiment of the present invention.
[0020]
In FIG. 1, reference numeral 1 denotes a battery pack that is mounted on a HEV or the like and is composed of a secondary battery, for example, a nickel-hydrogen battery. The battery pack 1 usually includes a first battery module 11, a second battery module 12, and a third battery in which a large number of unit cells, which are nickel-hydrogen batteries, are electrically connected in series in order to obtain a predetermined output to the motor. The module 13, the fourth battery module 14, and the fifth battery module 15 are further electrically connected in series. Each battery module 11, 12, 13, 14, 15 is divided into block units for detecting battery voltage, as will be described later. Further, as will be described later, the voltage of the first battery module 11 is detected on a cell-by-cell basis.
[0021]
The first battery module 11 is provided with a comparative determination unit cell 111 whose internal resistance always increases faster than other unit cells. This comparative determination unit cell 111 is configured to have a separator with a large weight per unit weight or a smaller amount of electrolyte than the other unit cells. Configured. In general, as charging / discharging is performed, the electrolyte solution of the separator is consumed due to expansion and oxidation of the electrode plate, and when the amount of liquid retained in the separator falls below a certain threshold, the internal resistance of the battery starts to increase. That is, since the comparison determination unit cell 111 has a smaller amount of liquid retained in the initial separator than the other unit cells, the amount of retained electrolyte in the separator is always lower than the threshold as charging / discharging is performed first. As a result, the internal resistance always rises quickly, and the deterioration always starts first.
[0022]
FIG. 2 shows a change in internal resistance with respect to a charge / discharge pulse cycle in a battery pack having a battery capacity of 10 Ah (31 g) with a reduced amount of electrolyte (31 g), a comparative judgment cell (curve A), and a normal amount of electrolyte. (37g) is a diagram comparatively illustrated with another unit cell (curve B). In FIG. 2, one charge / discharge cycle is composed of 20A, a charge pulse period of 1 minute, and 20A, a discharge pulse period of 1 minute. As shown in FIG. 2, the internal resistance of the single cell for comparison determination of the curve A increases faster than the other single cells of the curve B.
[0023]
Returning to FIG. 1 again, reference numeral 2 denotes a voltage detection switch for the battery pack 1, and the voltage of the comparison determination unit cell 111 and each of the first to fifth battery modules 11, 12, 13, 14, 15. Switches 20 and 21 for detecting the battery voltage as voltage samples V0 (n), V1 (n), V2 (n), V3 (n), V4 (n), and V5 (n) at predetermined time intervals in time series. , 22, 23, 24, 25.
[0024]
Reference numeral 3 denotes a temperature detection switch for the battery pack 1, and temperature sensors 41, 42, 43, 44 arranged in temperature coupling with the first to fifth battery modules 11, 12, 13, 14, 15. , 45 is a switch for detecting each battery temperature as temperature samples T1 (n), T2 (n), T3 (n), T4 (n), and T5 (n) at predetermined time intervals in a time series. 31, 32, 33, 34, 35.
[0025]
Reference numeral 4 denotes a current detector, which samples the charge / discharge current of the battery pack 1 output from a current sensor (not shown) at predetermined time intervals, acquires a current sample I (n), and detects the magnitude of the current. At the same time, the charge / discharge direction C / D, which is charging or discharging, is also detected by the sign.
[0026]
Reference numeral 5 denotes a battery controller, and voltage samples V0 (n), V1 (n), V2 () obtained by turning on the voltage detection switches 20, 21, 22, 23, 24, and 25 in time series by a control signal VC. n), V3 (n), V4 (n), V5 (n), and the temperature sample T1 (T) obtained by turning on the temperature detection switches 31, 32, 33, 34, and 35 in time series by the control signal TC. n), T2 (n), T3 (n), T4 (n), T5 (n), the current sample I (n) from the current detector 5 and the charge / discharge direction C / D, The remaining capacity is obtained by calculation, and is transmitted as battery information BI to an external system control unit (not shown) for charge / discharge control on the battery pack 1.
[0027]
Further, the battery controller 5 compares the remaining capacity obtained by the calculation based on the voltage sample V0 (n), the current sample I (n), and the charge / discharge direction C / D in the remaining capacity range where the internal resistance change is small. The internal resistance of the judgment cell 111 is calculated, and the voltage samples V1 (n), V2 (n), V3 (n), V4 (n), V5 (n), the current sample I (n), and the charge / discharge direction C Based on / D, the internal resistances of the other unit cells in each of the battery modules 11, 12, 13, 14, and 15 are calculated, and the internal resistances of the other unit cells are compared with the internal resistance of the comparison determination unit cell 111. Thus, the deterioration state of the battery pack is determined, and when it is determined that the end of the battery life is reached, a warning signal is transmitted by the battery information BI to an external system control unit (not shown).
[0028]
Next, a deterioration determination method for the battery pack system configured as described above will be described with reference to FIG.
[0029]
FIG. 3 is a flowchart showing a deterioration determination routine in the battery pack deterioration determination method according to the embodiment of the present invention.
[0030]
In FIG. 3, first, a voltage sample Vi (n), a current sample Ii (n), and a temperature sample Ti (n) of the comparative determination unit cell 111 and each of the battery modules 11, 12, 13, 14, and 15 are obtained. The remaining capacity SOCi (n) is calculated (S301). Next, in the remaining capacity range where the calculated remaining capacity SOCi (n) has a small internal resistance change, the voltage sample Vi (n) and the current sample Ii (n) are plotted, and Vi (n) −Ii (n) is plotted. From the characteristics, the internal resistance RA of the comparison determination unit cell 111 and the internal resistance RB of other unit cells are calculated (S302).
[0031]
Next, it is determined whether or not the difference value (RA−RB) between the internal resistance RA and the internal resistance RB exceeds a predetermined threshold Rs (S303). If RA-RB ≦ Rs as a result of this determination (No), it is determined that the battery pack 1 is not at the end of its life because the internal resistance RA of the comparison determination unit cell 111 has not increased and has not deteriorated. (S304), the process returns to step S301.
[0032]
On the other hand, as a result of the determination in step S303, when the charge / discharge cycle is repeated and the internal resistance RA of the cell for comparison determination 111 increases and RA-RB> Rs is satisfied (Yes), the deterioration is progressing. The battery pack 1 is determined to be at the end of its life (S305), and a warning signal is transmitted to the external system control unit (S306).
[0033]
【Effect of the invention】
As described above, according to the present invention, it is possible to provide a battery pack system and a battery pack deterioration determination method capable of safely and reliably performing end-of-life determination at low cost. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a battery pack according to an embodiment of the present invention. FIG. 2 is a diagram showing changes in internal resistance with respect to a charge / discharge pulse cycle. Flow chart showing a deterioration judgment routine in the judgment method [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Battery pack 2 Voltage detection switch 3 Temperature detection switch 4 Current detection part 5 Battery controller 111 Cell for comparison judgment

Claims (9)

A battery pack system having an assembled battery in which a plurality of single cells as secondary batteries are connected,
The assembled battery is provided with a comparative determination unit cell in which internal resistance always increases faster than other unit cells as charge / discharge is performed, and deterioration always starts first. Pack system. A current detection unit for detecting a current flowing in the assembled battery;
A first voltage detection unit for detecting a voltage of the battery for comparison determination;
A second voltage detector for detecting the voltage of the other unit cell in block units;
A first internal resistance calculation unit that calculates a first internal resistance of the comparison determination unit cell based on at least a current from the current detection unit and a voltage from the first voltage detection unit;
A second internal resistance calculator for calculating a second internal resistance of the other unit cell based on at least a current from the current detector and a voltage from the second voltage detector;
The battery pack system according to claim 1, further comprising a deterioration determination unit that performs battery deterioration determination based on the first internal resistance and the second internal resistance.   3. The battery pack system according to claim 1, wherein the comparative determination unit cell includes a separator having a larger weight per unit area than the other unit cell. 4.   3. The battery pack system according to claim 1, wherein the comparison determination unit cell is configured to have a smaller amount of electrolyte than the other unit cell.   The battery pack system according to any one of claims 1 to 4, wherein the secondary battery is a nickel-hydrogen secondary battery. A method of determining deterioration of a battery pack having an assembled battery in which a plurality of single cells as secondary batteries are connected,
As the battery pack is charged and discharged , the internal resistance always rises faster than other battery cells, and a battery for comparison and determination that always begins to deteriorate first is arranged.
Monitoring the first internal resistance of the comparative determination unit cell in units of cells;
Monitoring the second internal resistance of the other unit cell in units of blocks;
A battery pack deterioration determination method, wherein battery deterioration determination is performed by comparing the first internal resistance and the second internal resistance.   The battery pack deterioration determination method according to claim 6, wherein the comparison determination unit cell includes a separator having a larger weight per unit area than the other unit cell.   The battery pack deterioration determination method according to claim 6, wherein the comparison determination unit cell is configured to have a smaller amount of electrolyte than the other unit cell.   The battery pack deterioration determination method according to any one of claims 6 to 8, wherein the secondary battery is a nickel-hydrogen secondary battery.

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