JP5693302B2 - Battery system - Google Patents

Description

  The present invention relates to a battery system including a secondary battery having an electrode body and a battery container containing the electrode body.

  For example, in a secondary battery represented by a lithium ion secondary battery, in order to control charging / discharging of the secondary battery, the charging rate of the secondary battery (hereinafter referred to as SOC (State of Charge)) is monitored. There is a need to.

  As a method for obtaining this SOC, for example, there are the following methods.

  The first method is a method of constantly detecting the current value flowing through the terminal of the secondary battery and integrating the current value to obtain the SOC.

  Further, as described in Patent Document 1 below, for example, the second method focuses on the correlation between the OCV (Open Circuit Voltage) of the secondary battery and the SOC, detects the OCV, and detects this OCV. It is a method of calculating | requiring SOC from this. Since the OCV value changes due to an overvoltage due to the battery impedance in the energized state, the second method basically detects the OCV when the secondary battery is in the energized stop state, and energizes from this OCV. The SOC in the stop state is obtained. Further, in this second method, in order to obtain the SOC in the energized state, the battery impedance and the OCV in the energized state are detected, the OCV is corrected with this battery impedance, and the SOC is obtained from the corrected OCV. Yes.

JP 2007-24673 A

  However, in the first method, when the current value range of the current flowing through the terminal of the secondary battery is wide, for example, from 0.1 A or less to 100 A or more, a plurality of ammeters having different ranges are required, which is costly. There is also the problem of increasing.

  Further, the second method also requires a means for detecting the battery impedance in addition to the means for detecting the OCV in order to obtain the SOC in the energized state, which increases the cost.

  In view of the above, an object of the present invention is to provide a secondary battery system capable of obtaining the SOC by a simple method and reducing the cost with respect to the SOC in the energized state.

The secondary battery system according to the invention for solving the above problems is
A plurality of electrode bodies that are stacked, and a secondary battery having a battery case containing therein a plurality of electrode body,
And strain gauges for detecting the distortion of the battery container, a storage unit relationship information indicating the relationship is stored in the charging rate of the distortion and the secondary battery detected by the strain gauge, detected by the strain gauge using said distortion and said relationship information, e Bei and a calculation unit for determining the charging rate,
The battery container has a stacking direction surface facing a stacking direction in which a plurality of the electrode bodies are stacked, and the strain gauge is a portion having a large strain in a strain detection region detected by the strain gauge, It is provided in the edge part in a lamination direction surface, It is characterized by the above-mentioned.

  There is a high correlation between the distortion of the battery case and the charging rate of the secondary battery. For this reason, in the said secondary battery system, the charging rate of a secondary battery can be obtained from the distortion of the battery container detected by the distortion sensor.

  In the secondary battery system, since the strain at the position where the change in strain is large is detected by the strain sensor, the strain detection accuracy can be increased, and as a result, the charging rate accuracy can be increased.

  In the present invention, the charging rate of the secondary battery can be obtained from the strain of the battery container detected by the strain sensor. For this reason, according to the present invention, it is possible to obtain the charging rate in the energized state and to reduce the cost.

It is a perspective view of the secondary battery in one embodiment concerning the present invention. It is a lineblock diagram of the battery system in one embodiment concerning the present invention. It is a graph which shows the relationship between the voltage between terminals of a battery, and the distortion of a cell case (container). It is the IV-IV sectional view taken on the line in FIG.

  Hereinafter, embodiments of a battery system according to the present invention will be described with reference to the drawings.

  As shown in FIG. 2, the battery system 100 of the present embodiment includes a battery pack 101 including a plurality of lithium ion single cells (hereinafter simply referred to as batteries) 1 that are secondary batteries, and a control for controlling each battery 1. The circuit 105 and the ammeter 109 that detects the value of the current that the assembled battery 101 supplies to the power load 111 are provided. The battery system 100 is mounted on, for example, an electric vehicle. In this case, the power load 111 of the battery system 100 is a motor or the like.

  In the plurality of batteries 1, these electrode terminals are electrically connected to each other by a bus bar or the like to constitute the assembled battery 101 described above.

  The control circuit 105 is provided for each of the plurality of batteries 1. The CMU (Cell Monitoring Unit) 10 that monitors and controls the operation state of the battery 1, and the BMU (Battery Management Unit) that manages the operation of each CMU 10 and the state of each battery. ) 20. The CMU 10 for each battery 1 is connected to the BMU 20 in parallel by a bus, and transmits / receives data to / from the BMU 20.

  Here, the CMU 10 is provided for each battery 1, but the CMU 10 may be provided for each of several batteries 1, or one CMU 10 may be provided for the entire assembled battery 101. In addition, although the plurality of CMUs 10 and the BMU 20 are connected in parallel here, the plurality of CMUs 10 and the BMU 20 may be connected in a serial bus.

  Various sensors 9 for detecting the state of the battery 1 are attached to the battery 1. In this embodiment, one battery 1, various sensors 9 for the battery 1, and the CMU 10 for the battery 1 form a battery module 108. Outputs from the various sensors 9 are input to the CMU 10. The CMU 10 transmits output data from the various sensors 9 to the BMU 20 as necessary.

  A load control device 112 that controls the operation of the power load 111 is connected to the power load 111. When the battery system 100 is mounted on an electric vehicle, the load control device 112 is, for example, an ECU (Electronic Control Unit). The BMU 20 is connected to the load control device 112 via a bus, and transmits / receives data to / from the load control device 112. The load control device 112 is connected to an input device 113 that gives control instructions for the power load 111 and an output device 114 that outputs information about each battery 1.

  The input device 113 is, for example, switches on an instrument panel of a device in which the power load 111 is provided. The output device 114 is a display device that displays information about the power load 111 and each battery 1, a speaker that outputs sound, and the like.

  As shown in FIG. 1, the battery 1 includes a plurality of positive plates (positive electrode bodies) 4, a plurality of negative plates (negative electrode bodies) 2, a separator 3 that covers the negative plates 2, an electrolytic solution, And a cell case 6 (battery container) 6 for storing them. As the electrolytic solution of the battery 1, an aqueous solution is not used, and an organic solvent solution in which lithium ions are dissolved is used.

  Each of the electrode plates 2 and 4 is formed by applying an active material or the like to a sheet-like current collector. The current collector has a rectangular sheet-shaped main body and a tab extending from the edge of the rectangular sheet-shaped portion. The active material is applied to the main body of the current collector. The positive electrode plate 4 is coated with a positive electrode active material (for example, lithium manganate: LiMn2O2 or ternary material: LiNixCoyMnzO2 (x + y + z = 1)) on the current collector body such as aluminum foil. The positive electrode plate main body 4b and the above-described tab 4t not coated with the active material are provided. The negative electrode plate 2 is not coated with a negative electrode plate main body 2b in which a negative electrode active material (for example, carbon or artificial graphite) is coated on a main body of a current collector such as copper foil. It has the aforementioned tab 2t.

  The negative electrode plate body 2 b of the negative electrode plate 2 is completely covered with the separator 3, and a part of the tab 2 t of the negative electrode plate 2 is exposed from the separator 3. The separator 3 is formed of a resin having an insulating property and an electrolytic solution resistance, for example, a polyolefin such as polyethylene or polypropylene.

  The plurality of positive electrode plates 4 and the plurality of negative electrode plates 2 each covered with the separator 3 are alternately stacked such that the sides on which the tabs 4t and 2t are provided are the same side, and the electrode laminate 5 is formed.

  The cell case 6 is made of a metal such as aluminum. The cell case 6 includes a case main body 6m in which a rectangular parallelepiped storage recess into which the electrode laminate 5 is placed, and a lid 6n that closes the opening of the case main body 6m.

  Positive and negative electrode terminals 7a and 7b are fixed to the lid 6n of the cell case 6 via an insulating material. Further, a safety valve (not shown) and the like are also fixed to the lid 6n. The positive and negative electrode terminals 7a and 7b are fixed to the lid 6n in a state of passing through the lid 6n, and project to the inside and outside of the cell case 6.

  A lead 8a joined to the tab 4t of the positive electrode plate 4 is connected to the positive terminal 7a with a screw (not shown). Further, a lead 8b connected to the tab 2t of the negative electrode plate 2 is connected to the positive electrode terminal 7b with a screw (not shown).

  Among the wall surfaces forming the case main body 6m in which the rectangular parallelepiped storage recess is formed, the wall surface 6a facing the stacking direction L of the plurality of electrode bodies 2 and 4 stored in the case main body 6m is provided on the wall surface 6a. A strain gauge 9a which is one of the various sensors 9 is attached.

  The strain gauge 9a is connected to the CMU 10 through a signal line. The CMU 10 includes a CPU 11 that performs various calculations, a memory 12 that stores programs executed by the CPU 11, various data, and the like, and interfaces 14a and 14b for receiving and transmitting signals to and from the outside. Yes. The memory 12 stores relationship information F indicating the relationship between the strain detected by the strain gauge 9a and the charging rate of the battery 1 (hereinafter referred to as SOC (State of Charge)).

  By the way, as shown in FIG. 3, the inter-terminal voltage of the battery 1 and the distortion of the cell case 6 are highly correlated. Specifically, when the voltage between the terminals of the battery 1 is maximum, the distortion of the cell case 6 is maximized. When the voltage between the terminals of the battery 1 is reduced from the maximum value, the distortion of the cell case 6 is also reduced accordingly. Become. It is a well-known fact that there is a high correlation between the voltage between the terminals of the battery 1 and the SOC of the battery 1. Therefore, there is a high correlation between the SOC of the battery 1 and the distortion of the cell case 6.

  In the battery 1 of the present embodiment, Li ions are detached from the positive electrode plate 4 during charging, and the Li ions are inserted into the negative electrode plate 2, so that the electrode stack configured to include these electrode plates 4 and 2 is used. The body 5 expands, particularly in the stacking direction L of the electrode plates 4 and 2. On the contrary, during the discharge, the electrode laminate 5 is reduced, particularly in the stacking direction L of the electrode plates 4 and 2. As shown in FIG. 4, the cell case 6 expands and contracts in response to the expansion and contraction of the electrode laminate 5. Thus, since the cell case 6 expands and contracts due to charging / discharging of the battery 1, as described above, there is a high correlation between the SOC of the battery 1 and the strain of the cell case 6.

  Therefore, in the present embodiment, the wall surface 6a in which the distortion is greatest among the wall surfaces forming the cell case 6 due to the deformation of the cell case 6 due to charging / discharging of the battery 1, that is, the cell case 6 faces the stacking direction L. A strain gauge 9 a is provided on the wall surface 6 a, and the CMU 10 of the control circuit 105 obtains the SOC from the output from the strain gauge 9 a, that is, the strain of the cell case 6.

  In the memory 12 of the CMU 10, as described above, the relationship information F indicating the relationship between the strain detected by the strain gauge 9 a and the SOC of the battery 1 is stored in advance. This relationship information F can be obtained by, for example, actually charging and discharging the battery 1 by a test. The relationship information F may be information in the form of a function indicating the relationship between the SOC of the battery 1 and the strain of the cell case 6, or may be information indicating the strain of the cell case 6 for each SOC of the battery 1 in a table format. CPU11 which is a calculating part of CMU10 calculates | requires SOC using this relationship information F and the distortion detected by the strain gauge 9a.

  The CPU 11 of the CMU 10 stores the obtained SOC in the memory 12 at one end, and sends this SOC to the BMU 20 as necessary. The CMU 10 or the BMU 20 performs charge / discharge control or the like of the battery 1 according to the SOC.

  As described above, in the present embodiment, since the SOC is obtained from the strain of the cell case 6, it is possible to obtain the SOC even when the battery 1 is in the energized state or in the energized stop state.

  In this embodiment, the SOC can be obtained by providing the strain gauge 9a without providing a plurality of ammeters with different ranges, a means for detecting OCV (Open Circuit Voltage), and a means for detecting battery impedance. Therefore, the manufacturing cost of the battery 1 can be suppressed.

  In this embodiment, the strain of the cell case 6 is detected by the strain gauge 9a. However, any sensor may be used as long as the strain of the cell case 6 can be detected. For example, as shown in FIG. In addition, the optical displacement meter 9b may be used as a strain sensor.

  When the strain of the cell case 6 is detected by the optical displacement meter 9b, the displacement (distortion) of the central portion in the direction X perpendicular to the stacking direction L is the wall surface 6a of the cell case 6 facing the stacking direction L. This optical displacement meter 9b is preferably set so that it can be detected. This is because the center portion in the direction X in the wall surface 6a has the largest amount of displacement (strain).

  On the other hand, in this embodiment, the strain gauge 9a is provided at the end side in the direction X in the wall surface 6a. The strain gauge 9a is a sensor that detects a strain in a region where the strain gauge 9a is attached, that is, a limited strain detection region D. As described above, when the central portion in the direction X in the wall surface a of the cell case 6 has the largest amount of displacement (strain), but the central portion is the strain detection region D, the strain in the strain detection region D is On the other hand, when the end portion in the direction X in the wall surface 6a is the strain detection region D, the strain ε2 in the strain detection region D is large. For this reason, in this embodiment, the strain gauge 9a is provided in the portion in the cell case 6 where the strain in the strain detection region D is large, that is, in the end portion in the direction X in the wall surface 6a of the cell case 6. .

  In this embodiment, the SOC is obtained from only one strain in the cell case 6, but the temperature of the cell case 6 may also be detected, and the SOC may be obtained from this temperature and strain. The SOC may be obtained from strains at a plurality of locations in FIG.

  Since the elastic coefficient of the cell case 6 changes with temperature, the strain of the cell case 6 changes with the temperature change of the cell case 6. For this reason, a thermometer for detecting the temperature of the cell case 6 is provided, and relationship information F indicating the relationship between the temperature and strain of the cell case 6 and the SOC is stored in the memory 12, and the actually detected cell case is stored. The SOC may be obtained using the temperature and strain 6 and the relationship information F.

  Even if the distortion at the detection position assumed in advance in the cell case 6 is detected, the distortion at the detection position under the same condition is slightly different in each cell case 6 due to manufacturing errors of the cell case 6 and the like. For this reason, in order to level out variations in distortion due to manufacturing errors and the like, a plurality of strain sensors are provided, and relationship information F indicating the relationship between strain and SOC at each detection position of the cell case 6 is stored in the memory 12. Alternatively, the SOC may be obtained by using the distortion at each detection position actually detected and the relation information F.

  In this embodiment, the CMU 10 obtains the SOC from the distortion of the cell case 6, but the BMU 20 may obtain the SOC from the distortion of the cell case 6.

  1: battery, 2: negative electrode plate, 3: separator, 4: positive electrode plate, 5: electrode laminate, 6: cell case, 6a: wall surface, 6m: case body, 6n: lid, 9a: strain gauge, 9b: light Displacement meter, 100: battery system, 101: assembled battery, 105: control circuit

Claims (1)

A plurality of electrode bodies that are stacked, and a secondary battery having a battery case containing therein a plurality of electrode body,
A strain gauge for detecting strain of the battery case;
A storage unit storing relationship information indicating a relationship between the strain detected by the strain gauge and a charging rate of the secondary battery;
Using the strain detected by the strain gauge and the relationship information, a calculation unit for obtaining the charging rate,
Bei to give a,
The battery container has a stacking direction surface facing a stacking direction in which a plurality of the electrode bodies are stacked ,
The strain gauge is provided at an end in the laminating direction plane, which is a portion having a large strain in a strain detection region detected by the strain gauge .
A secondary battery system characterized by that.

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