JP2015153696A - Battery monitoring device and battery pack including battery monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery monitoring device in which expansion of all battery cells, the state of which is monitored, can be reflected on the monitoring, while reducing the number of sensors for detecting expansion of the battery cells.SOLUTION: A battery monitoring device for monitoring the state of charge of a battery pack 10 including a battery module pair where two battery modules 20, each including a plurality of battery cells 30 laminated tightly in a predetermined direction or laminated via a predetermined member 21, are arranged in a predetermined direction, includes a displacement sensor 25 provided between two battery modules 20 of the battery module pair, and measuring the distance between the battery modules 20, and an estimation unit for estimating the overcharged state of the battery pack 10, based on the distance measured by the displacement sensor 25.

Description

  The present invention relates to a battery monitoring device that detects expansion of an assembled battery, and an assembled battery including the battery monitoring device.

  Conventionally, there is an assembled battery device described in Patent Document 1 for detecting an overcharged state of a secondary battery. In the assembled battery device described in Patent Document 1, the swollenness detection element is arranged in the gap between the single cells, and the swollenness detection element operates based on the swollen deformation of the single battery, thereby detecting the overcharged state.

International Publication No. 2002/099922

  In the assembled battery device described in Patent Document 1, if the configuration is such that the bulge detection elements are provided in all the single cells, the number of bulge detection elements increases. On the other hand, if a configuration in which a swelling detection element is provided in some of the single cells, single cells that are not reflected in the detection of the overcharged state are generated.

  The present invention has been made to solve the above-described problems, and its main purpose is to reduce the number of sensors that detect the expansion of battery cells and to monitor the expansion of all battery cells that monitor the state. The object is to provide a battery monitoring device and an assembled battery that can be reflected.

  The present invention relates to a state of charge of a battery pack including a battery module pair in which two battery modules including a plurality of battery cells stacked in close contact with each other in a predetermined direction or in close contact via a predetermined member are arranged in a predetermined direction. A battery monitoring device for monitoring a battery, and a displacement sensor that is provided between two battery modules of a battery module pair and that measures the distance between the battery modules. An estimation unit for estimating the state of charge.

  Since the displacement sensor is provided between battery modules including a plurality of battery cells, the number of displacement sensors constituting the battery monitoring device can be reduced. Also, when the battery capacity increases due to charging and each battery cell expands, the battery modules are in close contact with each other in a predetermined direction or in close contact with each other through a predetermined member, so that the battery module expands in the predetermined direction. To do. Thereby, the distance between the two battery modules constituting the battery module pair is shortened. Therefore, by measuring the distance between the battery modules constituting the battery module pair by the displacement sensor, the expansion of all the battery cells included in the battery modules constituting the battery module pair is reflected in the estimation of the overcharge state. Can do. Furthermore, the amount of expansion per battery cell is small even in an overcharged state, and measurement is difficult. By measuring the distance between the battery modules including a plurality of battery cells, the total value of the expansion amounts of the plurality of battery cells can be acquired as the amount of change in the distance between the battery modules. Therefore, it is possible to accurately estimate the overcharged state of the assembled battery.

It is a side view of an assembled battery provided with a battery monitoring device. It is an example of attachment of a displacement sensor. (A) is a front view of a battery cell, (b) is the sectional view on the AA line of (a), (c) is the sectional view on the BB line of (a). The internal structure of a battery cell is shown, (a) is a front view, (b) is a view when (a) is viewed from the right side, and (c) is a view when (a) is viewed from below. It is a figure which shows the relationship between the distance between modules, SOC, and temperature. It is a figure which shows the relationship between the variation | change_quantity of the distance between modules, and SOC. It is a figure which shows the threshold value and temperature relationship which determine with an overcharge state. It is a flowchart of an overcharge state determination process.

  FIG. 1 is a side view of an assembled battery 10 including a battery monitoring device according to an embodiment. The assembled battery 10 is mounted on a vehicle such as a hybrid car, for example, and an overcharge state of the assembled battery 10 is estimated (monitored) and controlled by an ECU mounted on the vehicle. The assembled battery 10 includes a plurality of battery modules 20 arranged at predetermined intervals in a predetermined direction, and the battery modules 20 are provided on the heat exchanger 11. The battery module 20 is provided with a temperature sensor (not shown).

  The battery module 20 includes a plurality of plate-like battery cells 30 stacked in the same direction as the direction in which the battery module 20 is arranged. Between the battery cell 30 and the battery cell 30, every two heat conductive plates 21 made of metal such as aluminum are provided. In the heat conductive plate 21, the battery cells 30 are stacked on the heat exchanger 11. It is slidably installed in at least the same direction as the direction. A flange is formed at the lower end of the heat conducting plate 21. The flange facilitates heat conduction from the heat conduction plate 21 to the heat exchanger 11, and facilitates sliding of the heat conduction plate 21 along the upper surface of the heat exchanger 11.

  Restraint plates 22 are provided at both ends of the battery module 20, that is, at end portions in the stacking direction of the battery cells 30. The restraint plate 22 is fixed to the heat exchanger 11 by an L-shaped bracket 23 provided on the lower side, that is, on the heat exchanger 11 side. In addition, two belt-like restraining bands 24 are attached to the restraining plate 22 from the restraining plate 22 at one end toward the restraining plate 22 at the other end and at a predetermined interval in the vertical direction (vertical direction). ing. The restraint band 24 applies pressure to the battery module 20 so as to compress it in the stacking direction of the battery cells 30 (so as to shorten the length in the stacking direction). The two restraining bands 24 are attached so that the length of the restraining plate 22 in the vertical direction is substantially divided into three equal parts. For this reason, the restraint plate 22 and consequently the battery module 20 are restrained equally by the two restraint bands 24. Here, the restraint plate 22, the bracket 23, and the restraint band 24 constitute a restraint device.

  On the outer surface of the restraint plate 22 (the surface facing the adjacent restraint plate 22), a displacement sensor 25 that is a capacitance sensor that measures the distance from the restraint plate 22 of the adjacent battery module 20 is provided. The displacement sensor 25 is provided between the two restraining bands 24 on the outer surface of the restraining plate 22. Specifically, the displacement sensor 25 is provided at the center between the two restraining bands 24 in the vertical direction of the restraining plate 22. For this reason, the displacement sensor 25 can measure the displacement of the portion where the influence of the restraint of the restraining band 24 is small. The displacement sensor 25 is provided for every other battery module 20 arranged in a predetermined direction. That is, one displacement sensor 25 is provided for a pair of battery modules 20 (battery module pair). In FIG. 1, the wiring between the battery cells 30, the wiring between the battery modules 20, and the sensor cable that transmits the detection value of the displacement sensor 25 to the ECU are not shown.

  FIG. 2 shows an example in which the displacement sensor 25 is attached to the restraining plate 22. Here, the shape of the displacement sensor 25 is assumed to be a substantially disk shape.

  FIG. 2A shows an example in which a fixed guide 27 is provided on the restraint plate 22 and the displacement sensor 25 is secured to the restraint plate 22 with screws 27 ′. The fixed guide 27 supports the lower part of the displacement sensor 25. The fixed guide 27 has an inner diameter slightly larger than the outer diameter of the displacement sensor 25 and has an arc shape having a notch in a part thereof, and a hole portion into which a screw 27 ′ can be inserted into a part of the arc shape portion. Is formed. The displacement sensor 25 is fixed so that the detection surface faces outward. The sensor cable 26 that transmits the detection value of the displacement sensor 25 to the ECU extends to the outside of the battery module 20 through the notch of the fixed guide 27.

  FIG. 2B shows an example in which a groove 28 is formed in the constraining plate 22 and a displacement sensor 25 is fitted in the groove 28 (recess or notch). The displacement sensor 25 is provided with a protrusion that fits into the groove 28, and the protrusion of the displacement sensor 25 and the groove 28 are arranged so that the detection surface of the displacement sensor 25 is exposed to the outside of the restraint plate 22. Fit and fix. A sensor cable 26 that transmits the detection value of the displacement sensor 25 to the ECU extends to the outside of the battery module 20 through between the restraint plate 22 and the battery cell 30.

  FIG. 2C shows an example in which the displacement sensor 25 is attached to a hat-type metal fitting 29 (attachment tool), and the hat-type metal fitting 29 is further attached to the restraining plate 22. That is, the displacement sensor 25 is attached to the restraining plate 22 by the hat-shaped metal fitting 29. The hat-shaped metal fitting 29 has a pair of vertical wall portions opposed to each other with a space therebetween, a ceiling portion laid between one end edges of the vertical wall portion, and a pair of vertical wall portions facing each other from the other end edge of the vertical wall portion. And a flange portion extending in the opposite direction. The ceiling portion has at least a hole portion into which the sensor cable 26 can be inserted, and the flange portion has a hole portion into which the screw 29 ′ can be inserted. The displacement sensor 25 is fixed to the hat-shaped metal fitting 29 by passing the sensor cable 26 through the hole and fixing the detection surface of the displacement sensor 25 so as to be exposed in a direction opposite to the direction in which the vertical wall portion is provided. It is attached. The hat-shaped metal fitting 29 is attached to the restraining plate 22 through a flange portion with a screw 29 '. The sensor cable 26 extends from between the vertical wall portions to the outside of the battery module 20.

  3 shows the appearance of the battery cell 30, FIG. 3 (a) is a front view of the battery cell 30, FIG. 3 (b) is a cross-sectional view taken along line AA of FIG. 3 (a), and FIG. 3 (c). These are BB sectional drawing of FIG.3 (b). The battery cells 30 are stacked in the front direction to constitute the battery module 20. The battery cell 30 is obtained by coating an electrode body 31 provided with a positive electrode body and a negative electrode body with a laminate film 32, with the positive electrode terminal 33 exposed from one side surface of the battery cell and the negative electrode terminal 34 exposed from the other side surface. doing.

  FIG. 4 shows the structure of the battery cell 30 before being covered with the laminate film 32. 4 (a) is a front view of the battery cell 30, FIG. 4 (b) is a side view of the battery cell 30 as viewed from the negative electrode terminal 34 side, and FIG. 4 (c) is a view of the battery cell 30 below FIG. 4 (a). It is the figure seen from. The battery cell 30 includes a plurality of positive plates and a plurality of negative plates. The positive electrode plate has a rectangular shape, and a positive electrode current collector foil portion 35 in which the positive electrode active material is not applied to the surface of the current collector foil, and a positive electrode current collector portion 36 in which the positive electrode active material is applied to the surface of the current collector foil. It consists of. The positive electrode current collector foil portion 35 is provided on one short side of the positive electrode plate and has a certain width from the short side. The positive electrode current collector 36 is a portion of the positive electrode plate excluding the positive electrode current collector foil portion 35. The negative electrode plate has the same shape as the positive electrode plate, and the negative electrode current collector foil portion 37 in which the negative electrode active material is not applied on the surface of the current collector foil, and the negative electrode current collector in which the negative electrode active material is applied on the surface of the current collector foil Part 38. The negative electrode current collector foil portion 37 and the negative electrode current collector portion 38 have shapes common to the positive electrode current collector foil portion 35 and the positive electrode current collector portion 36, respectively.

  The positive electrode current collector 36 and the negative electrode current collector 38 are alternately stacked with separators 39 having the same shape as the positive electrode current collector 36 and the negative electrode current collector 38 interposed therebetween. At this time, the positive electrode current collector 36, the negative electrode current collector 38, and the separator 39 overlap each other. Moreover, the positive electrode current collector foil part 35 and the negative electrode current collector foil part 37 are directed to the opposite sides. A positive electrode terminal 33 is attached to the positive electrode current collector foil portion 35 of one positive electrode plate among the plurality of positive electrode plates, and a negative electrode is connected to the negative electrode current collector foil portion 37 of one negative electrode plate among the plurality of negative electrode plates. A terminal 34 is attached.

  The separator 39 is a polyolefin-based porous polymer film, and separates the positive electrode current collector 36 and the negative electrode current collector 38 to prevent a short circuit and allow lithium ions to pass therethrough.

  FIG. 5 is a graph showing the correlation between the inter-module distance and the SOC. The horizontal axis in FIG. 5 indicates the inter-module distance measured by the displacement sensor 25, and the vertical axis indicates the SOC. Moreover, the correlation between the distance between modules and SOC in the case of temperature T1, temperature T2, and temperature T3 is shown (where T1 <T2 <T3). That is, the higher the SOC, the larger the expansion amount of the battery cell 30 and the shorter the inter-module distance. Moreover, the lower the temperature, the larger the expansion amount of the battery cell 30 and the shorter the inter-module distance.

  FIG. 6 is a graph showing the correlation between the change amount δ of the inter-module distance and the SOC. The change amount δ is obtained by subtracting the initial value of the inter-module distance from the inter-module distance measured by the displacement sensor 25. As shown in FIG. 5, since the inter-module distance varies depending on the temperature, the initial value of the inter-module distance is associated with the temperature, and the initial value of the inter-module distance is determined by the temperature measured by the temperature sensor. For example, the distance between modules when the SOC is 60% is selected. Therefore, the inter-module distance variation δ is calculated from the inter-module distance measured by the displacement sensor 25 and the initial value of the inter-module distance selected based on the temperature measured by the temperature sensor. Here, if the amount of change δ takes a negative value, it means that the SOC has become less than the initial value, and if the amount of change δ takes a positive value, it means that the SOC has become greater than the initial value. Show. Then, when the change amount δ of the inter-module distance when the SOC is larger than the initial value, for example, 95%, is set as a threshold value, and the change amount δ of the inter-module distance becomes a value larger than the threshold value, the ECU It is estimated that the assembled battery 10 is in an overcharged state. Here, the ECU functions as an estimation unit.

  FIG. 7 is a graph showing the correlation between the distance change threshold and the temperature. As shown in FIG. 5, the higher the temperature, the smaller the expansion amount associated with the change in the SOC of the battery cell 30. Therefore, the higher the temperature, the smaller the change amount threshold, and the lower the temperature, the larger the change amount threshold. That is, the higher the temperature, the smaller the threshold value of the change amount, and the higher the temperature, the easier it is estimated that the overcharged state is established.

  FIG. 8 is a flowchart when the charge amount suppression control is performed. The flowchart shown in FIG. 8 is executed by the ECU at a predetermined cycle.

  First, the cell temperature T measured by the temperature sensor is acquired (S101), and it is determined whether or not the cell temperature T is less than a threshold value (S102). If it is determined that the cell temperature T is not less than the threshold (S102: NO), the cell is overheated, so the main relay is shut off (S103) and the process is terminated.

  On the other hand, when it is determined that the cell temperature T is less than the threshold (S102: YES), the correlation between the measured cell temperature T and the threshold of the change amount of the inter-module distance shown in FIG. In addition to selecting a threshold for the change amount of the inter-module distance, the inter-module distance at which the measured SOC at the cell temperature T is 60% is selected as the initial inter-module distance value X0 (S104). On the other hand, the inter-module distance X detected by the displacement sensor 25 is acquired (S105), and the inter-module distance change δ is calculated by subtracting the initial inter-module distance value X0 from the acquired inter-module distance X. (S106). Then, it is determined whether or not the change amount δ is larger than the threshold value (S107). If it is determined that the amount of change δ is greater than the threshold (S107: YES), a charge amount suppression command is output (S108). On the other hand, if it is not determined that the amount of change δ is greater than the threshold (S107: NO), the series of processing ends.

  This embodiment has the following effects by the above configuration.

  -Since the displacement sensor 25 is provided between the battery modules 20 containing the some battery cell 30, the number of the displacement sensors 25 which comprise a battery monitoring apparatus can be reduced. Further, when the battery capacity increases due to charging and each battery cell 30 expands, the battery cells 30 are stacked in close contact with each other or through the heat conduction plate 21 in the predetermined direction. Inflates. Thereby, the distance between the two battery modules 20 constituting the battery module pair is shortened. Therefore, by measuring the distance between the battery modules 20 constituting the battery module pair by the displacement sensor 25, the expansion of all the battery cells 30 included in the battery module 20 constituting the battery module pair is detected as an overcharged state. Can be reflected. Furthermore, the amount of expansion per battery cell is small even in an overcharged state, and measurement is difficult. By measuring the distance between the battery modules 20 including the plurality of battery cells 30, the total expansion amount of the plurality of battery cells 30 can be acquired as the amount of change in the distance between the battery modules 20. Therefore, the overcharged state of the assembled battery 10 can be accurately determined.

  -A lithium ion battery has the characteristic that the amount of expansion resulting from the state of charge increases as the temperature decreases. Therefore, when the threshold value is not changed, if the temperature is higher than the temperature assumed when the threshold value is set, the distance change amount is less than the threshold value, even though it is not estimated that the battery is overcharged. There is a risk of overcharging. On the other hand, if the temperature is lower than the temperature assumed when setting the threshold value, the amount of change in the distance is not less than the threshold value, and even if it is estimated that the battery is in an overcharged state, it may not actually be in an overcharged state. is there. In the present embodiment, a temperature sensor that measures the temperature of the battery module 20 is provided, and the threshold value of the change amount δ is set lower as the temperature measured by the temperature sensor is higher. Therefore, if the temperature is high, it can be estimated that the battery is overcharged even if the amount of change in distance is small. Also, if the temperature is low, it is not estimated that the battery is overcharged if the distance change is small.

  -Since the assembled battery 10 is comprised by the some battery module 20, when any battery module 20 deteriorates, only the deteriorated battery module 20 can be replaced | exchanged.

  -Since the displacement sensor 25 is provided for every battery module pair, it is not necessary to provide the displacement sensor 25 between all the battery modules 20, and the number of the displacement sensors 25 can be reduced. In addition, the expansion of all the battery cells 30 included in the assembled battery 10 can be reflected in the estimation of the overcharge state while reducing the number of the displacement sensors 25.

  The restraint plate 22 is provided at both ends of the battery module 20, and the lower end of the restraint plate 22 is joined to the heat exchanger 11. Furthermore, a restraint band 24 is provided to apply pressure to the battery module 20. Therefore, the electrodes in the battery cell 30 can be brought into close contact with each other, the reaction in the battery cell 30 is stabilized, and the power generation efficiency is increased. Moreover, since the clearance gap between the battery cells 30 can be reduced more, when measuring the distance between the battery modules 20 with the displacement sensor 25, the distance according to the expansion amount based on a charge condition can be measured more. .

  When a cooling air flow path formed of resin is provided between the battery cells 30, shrinkage (creep deformation) of components constituting the cooling air flow path may occur. Therefore, the restraint load applied to the battery module 20 from the restraint device including the restraint plate 22, the bracket 23, and the restraint band 24 needs to be set high considering the contraction. In this embodiment, since the flow path of the cooling air is not provided between the battery cells 30, the restraint load of the restraint device can be reduced, and the suppression of the change of the battery cell 30 by the restraint device can be reduced. Thereby, the change in the distance between the battery modules 20 becomes more based on the charged state, and the overcharged state can be accurately determined. In addition, since the heat conductive board 21 is formed with the metal, shrinkage | contraction can be suppressed.

  -If the heat conductive plate 21 is a structure which does not slide with respect to a thermal radiation part, the expansion of the battery cell 30 will be inhibited by the heat conductive plate 21. FIG. Since the heat conducting plate 21 and the heat radiating portion are slidably contacted, the expansion of the battery cell 30 is not hindered by the heat conducting plate 21, and the expansion of the battery module 20 can be detected more accurately. It becomes possible.

<Modification>
In the above embodiment, whether or not the overcharge state is estimated by determining whether or not the change amount δ of the inter-module distance exceeds the threshold value, but the inter-module distance X is shorter than the threshold value. It may be determined whether or not the battery is in an overcharged state by determining whether or not it has become.

  -In the said embodiment, although it was assumed that it was an overcharge state, it is good also as what estimates SOC. From FIG. 5, the SOC can be estimated by measuring the temperature and the distance between the modules. Further, in the estimation of the SOC, the SOC may be estimated using the change amount δ of the inter-module distance.

  In the above embodiment, the displacement sensors 25 are provided every other battery module 20 arranged in a predetermined direction, but may be provided in all battery modules 20. In addition, the displacement sensor 25 may be provided only in the battery module 20 placed in a high temperature environment in which the battery cells 30 are likely to deteriorate.

  In the above embodiment, the battery cell 30 is a laminate type lithium ion battery, but it may be a can type lithium ion battery. A battery other than the lithium ion battery can also be employed as the battery cell 30.

  In the above embodiment, the displacement sensor 25 is a capacitance sensor. However, a displacement sensor other than the capacitance sensor, for example, an eddy current sensor or the like can also be employed.

  In the said embodiment, although the example of attachment of the displacement sensor 25 was shown in FIG. 2, other attachment methods can also be employ | adopted.

  In the above embodiment, the number of the restraining bands 24 is two, but may be other than two. In addition, the two restraining bands 24 are attached so that the length of the restraining plate 22 in the vertical direction is divided into approximately three equal parts, but the attaching method of the restraining band 24 is not limited to this.

  In the above embodiment, the inter-module distance when the SOC is 60% is the initial value X0 of the inter-module distance, but the inter-module distance when the SOC is other than 60% is the initial value X0 of the inter-module distance. Also good. In addition, the amount of change δ between the modules when the SOC is 95% is used as a threshold for determining whether or not the battery is in an overcharged state. However, the SOC for determining whether or not the battery is overcharged is limited to 95%. It will never be done.

  In the said embodiment, although the assembled battery 10 shall be mounted in vehicles, such as a hybrid car, it is good also as what is mounted in vehicles other than a vehicle.

  DESCRIPTION OF SYMBOLS 10 ... Battery assembly, 20 ... Battery module, 21 ... Heat conduction board, 25 ... Displacement sensor, 30 ... Battery cell.

Claims (8)

A battery module pair in which two battery modules (20) including a plurality of battery cells (30) stacked in close contact with each other in a predetermined direction or in close contact via a predetermined member (21) are arranged in the predetermined direction. A battery monitoring device for monitoring the state of charge of the assembled battery (10) including:
A displacement sensor (25) provided between the two battery modules of the battery module pair for measuring a distance between the battery modules;
An estimation unit that estimates an overcharged state of the assembled battery based on the distance measured by the displacement sensor;
A battery monitoring device comprising: A battery module pair in which two battery modules (20) including a plurality of battery cells (30) stacked in close contact with each other in a predetermined direction or in close contact via a predetermined member (21) are arranged in the predetermined direction. A battery monitoring device for monitoring the state of charge of the assembled battery (10) including:
A displacement sensor (25) provided between the two battery modules of the battery module pair for measuring a distance between the battery modules;
Based on the distance measured by the displacement sensor and a correlation between the distance and the state of charge, an estimation unit that estimates a state of charge of the assembled battery;
A battery monitoring device comprising: The battery monitoring device further includes a temperature sensor that measures the temperature of the battery module,
The estimation unit makes it easier to estimate an overcharged state in the estimation of the overcharged state based on the distance measured by the displacement sensor, as the temperature measured by the temperature sensor is higher. The battery monitoring apparatus according to 1. The battery monitoring device further includes a temperature sensor that measures the temperature of the battery module,
The estimation unit estimates the charging state higher in the estimation of the charging state based on the distance measured by the displacement sensor as the temperature measured by the temperature sensor is higher. The battery monitoring device described. The estimation unit of the battery monitoring device according to claim 1 or 2,
A plurality of battery module pairs;
The displacement sensors respectively provided in the battery module pair;
A battery pack comprising: The estimation unit of the battery monitoring device according to claim 3 or 4,
A plurality of battery module pairs;
The displacement sensors respectively provided in the battery module pair;
A temperature sensor for measuring the temperature of the battery module;
A battery pack comprising:   The assembled battery according to claim 5 or 6, further comprising a restraining device (22, 23, 24) for applying pressure so as to reduce a length of the battery module in the predetermined direction. The predetermined member is a heat conductive plate that conducts heat of the battery cell to the heat radiating portion (11),
The assembled battery according to any one of claims 5 to 7, wherein the plurality of battery cells are stacked in close contact with each other through the heat conducting plate in the predetermined direction.