JP5907050B2 - Battery system - Google Patents

Description

  The present invention relates to a battery system in which an output voltage of each unit battery is detected for an assembled battery having a plurality of unit batteries connected in series.

  For example, as an in-vehicle power source, an assembled battery that outputs a high voltage by connecting a plurality of battery cells in series is used. With respect to the plurality of battery cells constituting the assembled battery, each output voltage at the time of charging / discharging is detected by the voltage detecting means. And the overcharge and overdischarge of a battery cell can be suppressed by controlling charging / discharging in a battery cell based on the detected output voltage.

  For example, in Patent Document 1 below, a voltage for sequentially detecting the voltage of each battery cell by selectively connecting both output terminals of each battery cell constituting the assembled battery to a pair of input terminals of the voltage detection means. A detection device is described.

Japanese Patent Laid-Open No. 11-150877

  Here, the assembled battery includes a conductive member (wiring or bus bar) that connects output terminals of a plurality of adjacent battery cells. As a method of detecting the output voltage of the battery cell, instead of connecting the voltage detection means to both output terminals of the battery cell, the conductive member for connecting the output terminals of the battery cells and the voltage detection means are connected. Method is used.

  By connecting the input terminal of the voltage detection means to the conductive member and detecting the voltage, it is possible to detect the voltage at the output terminals of the plurality of battery cells connected to the conductive member. Thereby, the number of wiring which connects an assembled battery and a voltage detection apparatus can be reduced.

  Here, the conductive member has a resistance component. For this reason, when the conductive member that connects the storage batteries and the input terminal of the voltage detection means are connected, the voltage that is decreased or increased by the amount of voltage drop due to the resistance component of the conductive member to the actual output voltage of the battery cell. Is detected as the output voltage of the battery cell.

  The present invention has been made in view of the above problems, and an object of the present invention is to accurately detect the output voltage of each of a plurality of unit batteries constituting an assembled battery.

The first configuration includes a plurality of unit cells ( 13, 43), the unit cells are arranged next to each other, and conductive members (14, 15) are provided on the positive electrode side and the negative electrode side of each unit cell. An assembled battery (10, 40) in which the unit cells are connected in series by electrically connecting the electrodes of the adjacent unit cells by the conductive member, and the positive side of the unit cell; Voltage detection means (21) for detecting an output voltage for each unit battery based on a voltage difference between the conductive members on the negative electrode side, and a voltage drop for calculating a voltage drop amount due to a resistance component of the conductive member for each unit battery Amount calculating means (26), and correcting means (27) for correcting the output voltage of the unit battery detected by the voltage detecting means with the voltage drop amount calculated by the voltage drop amount calculating means. A battery system characterized by obtaining.

  According to the above configuration, the output voltage of the unit battery can be accurately detected by correcting the output voltage of the unit battery using the voltage drop amount due to the conductive member. Thereby, charging / discharging control of a unit battery can be performed suitably, and eventually charging / discharging control of an assembled battery can be performed suitably.

Schematic which shows an assembled battery. The circuit diagram which shows the connection of a voltage detection means. The figure which shows the charging / discharging control of a battery cell. The figure which shows the internal resistance for every battery cell. The functional block diagram which shows a battery system. The correspondence table of a cell number and a conductive member, and the correspondence table of a conductive member and a resistance value. The flowchart which shows the voltage detection process of this embodiment. Schematic which shows the assembled battery in a modification.

  Hereinafter, an embodiment as an in-vehicle power supply system will be described. First, the configuration of the assembled battery as a power source will be described. The assembled battery includes a plurality of battery cells constituting a unit battery, and a series connection body formed by connecting them in series is accommodated in a case member. An output voltage is detected for each battery cell, and a state of charge (SOC) of each battery cell is calculated based on the detected output voltage.

  In the assembled battery, each battery cell is arranged as shown in FIG. The assembled battery 10 according to the present embodiment includes two battery modules 11 and 12, and each of the battery modules 11 and 12 includes 12 battery cells 13. The battery cell 13 consists of a lithium ion storage battery, and has comprised the rectangular parallelepiped shape, respectively. Hereinafter, the two battery modules 11 and 12 are also referred to as a first battery module 11 and a second battery module 12. For convenience of explanation, cell numbers such as C1, C2, C3... Are assigned to the battery cells 13, for example, the battery cell 13 with the cell number C1 is “battery cell C1” and the battery cell 13 with the cell number C2 is Also referred to as “battery cell C2”. The number of battery modules and the number of cells in each battery module may be arbitrary.

  In each of the battery modules 11 and 12, six battery cells 13 are arranged in rows to form a cell row, and the cell rows are provided in two rows. A bus bar 14 as a conductive member is connected to the positive electrode side and the negative electrode side of each battery cell 13, and the electrodes of adjacent battery cells 13 are electrically connected by the bus bar 14.

  Specifically, the battery cells 13 arranged in the upper and lower directions in the figure are arranged so that the positive electrode and the negative electrode are alternated, and the positive electrode of one battery cell 13 and the other battery cell 13 of adjacent battery cells 13. A bus bar 14 is provided so as to span the negative electrode of the cell, and the bus bar 14 electrically connects the cells. Each battery cell 13 may have a shape other than a rectangular parallelepiped shape, or may have a cylindrical shape or a prismatic shape.

  In the first battery module 11, the positive electrode side of the battery cell C <b> 1 is a positive output terminal in the assembled battery 10, and in the second battery module 12, the negative electrode side of the battery cell C <b> 24 is a negative output terminal in the assembled battery 10. Yes. Further, the two battery modules 11 and 12 are connected via an electric wiring 15. Specifically, the bus bar 14 connected to the negative electrode of the battery cell C12 in the first battery module 11 and the bus bar 14 connected to the positive electrode of the battery cell C13 in the second battery module 12 serve as an electrical wiring 15 as a conductive member. Connected through.

Here, the bus bar 14 connected to the positive electrode side and the negative electrode side of each battery cell 13 has a different shape and size depending on which battery cell 13 is provided.
(1) A bus bar for connecting adjacent battery cells in the same cell row of the same battery module (14a in the figure)
(2) Bus bar for connecting cell rows in the same battery module (14b in the figure)
(3) A bus bar (14c in the figure) serving as a positive output terminal of the assembled battery 10 in the first battery module 11
(4) A bus bar (14d in the figure) serving as the negative output terminal of the battery pack 10 in the second battery module 12
Can be broadly divided.

  Each of these bus bars 14 has a different shape and size depending on various factors such as a distance between connected ones, that is, a distance between electrodes and interference with other members.

  By the way, in the assembled battery 10, as shown in FIG. 2, each battery cell 13 is individually connected to the voltage detection means 21, and an output voltage is detected for every battery cell 13. As shown in FIG. In this case, the cell voltage detection line 22 is connected to the bus bar 14 connected to each electrode of the battery cell 13, and in the voltage detection means 21, the voltage difference between the bus bars 14 is used as the output voltage of each battery cell 13. It is to be detected. In FIG. 1, the position indicated by “P” is the connection position of the cell voltage detection line 22 in the bus bar 14.

  When the voltage detection means 21 detects the output voltage of the battery cell 13 in this way, the connection between the connection position P of the bus bar 14 connected to the positive electrode and the negative electrode of the battery cell 13 and the positive electrode and the negative electrode of the battery cell 13. There is a concern that the detection accuracy of the output voltage of the battery cell 13 is lowered due to the resistance. More specifically, as shown in FIG. 3, the difference between the detected value of the output voltage of the battery cell 13 and the actual value is proportional to the value of the current flowing through the battery cell 13. There is a concern that the detected value is higher than the actual value of the output voltage of the battery cell 13 during charging, and the detected value is lower than the actual value of the output voltage of the battery cell 13 during discharging.

  In FIG. 3, when the output voltage of the battery cell 13 reaches a predetermined voltage value (overcharge threshold), charging the battery cell 13 is prohibited so that the battery cell 13 is not overcharged. When the battery cell 13 is charged, that is, during the time when the current value of the charge / discharge current is positive, a positive counter electromotive force is generated in the resistance of the bus bar 14 and the electric wiring 15. When the detected value of the output voltage of the battery cell 13 becomes higher than the actual value due to the positive counter electromotive force, the battery cell 13 is charged even though the actual value of the output voltage of the battery cell 13 has not reached the overcharge threshold. Will be banned.

  Further, when the output voltage of the battery cell 13 reaches a predetermined voltage value (overdischarge threshold), discharge in the battery cell 13 is prohibited so that the battery cell 13 is not overdischarged. When the battery cell 13 is discharged, that is, during the time when the current value of the charge / discharge current is negative, a negative counter electromotive force is generated in the resistance of the bus bar 14 and the electric wiring 15. When the detected value of the output voltage of the battery cell 13 becomes lower than the actual value due to the negative counter electromotive force, the actual value of the output voltage of the battery cell 13 does not reach the overdischarge threshold, but the battery cell 13 Discharging is prohibited.

  As described above, since the internal resistance of the battery cell 13 is detected by increasing the resistance of the bus bar 14, there arises a disadvantage that a voltage region in which charging / discharging of the battery cell 13 is permitted is narrowed. When any one of the battery cells 13 constituting the assembled battery 10 reaches the overdischarge threshold, the assembled battery 10 prohibits the discharge of the entire assembled battery 10, and any one of the battery cells 13 is overcharged. If it reaches, charging of the whole assembled battery 10 is prohibited. For this reason, if any one of the bus bar 14 and the electrical wiring 15 has a high resistance value, the region of the output voltage permitted to be charged / discharged in the entire assembled battery 10 is narrowed.

  Further, as described above, in the battery pack 10, the bus bar 14 includes parts having different shapes and dimensions, and it is conceivable that the value of the internal resistance is different for each bus bar 14. In this case, the internal resistance (error) of the bus bar 14 in the detected voltage is different for each battery cell 13, and the difference in the internal resistance is shown in FIG. In FIG. 4, the value of the internal resistance is shown for each cell number of the battery cell 13 (for convenience, “C” is shown).

  In FIG. 4, for example, when the battery cells C1 to C12 included in the first battery module 11 are viewed, the internal resistances of the battery cells C1 to C5 and C7 to C11 are substantially the same. The slight difference in the internal resistance value in each cell takes into account the connection position P (see FIG. 1) of the cell voltage detection line 22 in the bus bar 14 and various circumstances in the actual configuration. Note that a bus bar 14b (long bus bar) for inter-column connection is used on the positive electrode side of the battery cell C7, but the connection position P of the cell voltage detection line 22 is closer to the positive electrode of the battery cell C7. Therefore, the difference in internal resistance is small (see FIG. 1).

  On the other hand, in the battery cell C6, the bus bar 14b (long bus bar) for inter-column connection is used on the negative electrode side, so that the value of the resistance detected as the internal resistance is large. Further, in the battery cell C12, since the electric wiring 15 is connected to the bus bar 14 on the negative electrode side, the resistance value detected as the internal resistance is increased accordingly.

  The same applies to the second battery module 12, and the internal resistances of the battery cells C13 to C17 and C19 to C24 are substantially the same, whereas the resistance of the bus bar 14b for connecting the columns is detected as the internal resistance. The internal resistance is increasing.

  In the design stage of the battery pack 10, it is possible to suppress an increase in resistance and a variation in resistance due to the bus bar 14 and the electric wiring 15. However, it is difficult to completely eliminate the influence of these resistors. Moreover, in order to reduce these resistance values, there is a concern about an increase in manufacturing cost of the assembled battery 10. Specifically, as a method for suppressing the increase in resistance, it is conceivable to increase the cross-sectional area of the bus bar 14 or to select a material having good conductivity for the bus bar 14. In addition, as a method of suppressing resistance variation, it is conceivable to intentionally make a bus bar with relatively low resistance thin, for example, to match a bus bar with relatively high resistance, but the design becomes complicated and the cost increases. Concerned.

  Therefore, the present embodiment suppresses the influence of the voltage drop due to the resistance of the bus bar 14 in the detection of the output voltage of the battery cell 13. Specifically, the voltage drop amount in each bus bar 14 is calculated using the resistance value of each bus bar 14 and the electrical wiring 15 connecting the bus bars 14 and the current value I of the discharge current flowing through the assembled battery 10, The output voltage of each battery cell 13 is corrected using the calculated voltage drop amount.

  Next, the configuration of the power supply system of this embodiment will be described with reference to FIG. The voltage detection apparatus 20 included in the battery system includes a voltage detection unit 21, a current detection unit 23, a temperature detection unit 24, a storage unit 25, a voltage drop amount calculation unit 26, and a correction unit 27.

  The voltage detection means 21 is a circuit that has a voltmeter including a voltage dividing resistor and an amplifier and a multiplexer (MPX), detects the voltage of each battery cell 13, and outputs the detected value as a signal. The voltage detection means 21 is connected to the bus bar 14 at the connection position P via the cell voltage detection line 22. And the voltage detection means 21 detects the voltage difference between the adjacent connection positions P as an output voltage of the battery cell 13 pinched | interposed into both the connection positions P. FIG.

  The current detection means 23 detects the current value of the charge / discharge current flowing through the assembled battery 10 based on, for example, an output signal from the Hall element, and outputs it as a detection signal Sa. The temperature detection means 24 detects the temperature of the battery modules 11 and 12 based on the output signals from the thermistors T1 and T2, and outputs them as a detection signal St.

  The storage means 25 is composed of, for example, a ROM, and the storage means 25 stores a combination of the cell number of each battery cell 13 and the bus bar 14 and electrical wiring 15 detected as the resistance value of the battery cell 13 as a map. ing. Specifically, as shown in FIG. 6A, cell connection bus bars 14a in the same cell row correspond to cell numbers C1 to 5, C7 to 11, C13 to 17, and C19 to 23. Further, inter-row connection bus bars 14b correspond to the cell numbers C6 and C18. Further, the negative electrode bus bar 14 d of the battery module 11, the positive electrode bus bar 14 c of the battery module 12, and the series connection body of the electric wiring 15 correspond to the cell number C 12. The negative electrode bus bar 14d of the battery module 12 corresponds to the cell number C24.

  Further, the storage means 25 stores the resistance value at the reference temperature for the resistance of both bus bars 14 and electrical wiring 15 between the connection positions P of both bus bars 14 connected to the positive electrode side and the negative electrode side of the battery cell 13. Has been. Specifically, the resistance value Ra of the bus bar 14a, the resistance value Rb of the bus bar 14b, the resistance value Rc of the serial connection body of the bus bar 14c, the bus bar 14d, and the electric wiring 15, and the resistance value Rd of the negative bus bar 14d (this embodiment) Then, Rd = 0) is stored as a map shown in FIG. Here, the resistance value Rd of the bus bar 14d for the negative electrode is 0 because the negative electrode of the battery cell 13 and the connection position P in the bus bar 14d are close enough to ignore the resistance value by the bus bar 14d. is there.

  The voltage drop amount calculation means 26 reads out from the storage means 25 the types of the bus bar 14 and the electrical wiring 15 detected as the resistance value of the battery cell 13 corresponding to each battery cell 13. Further, the voltage drop amount calculation means 26 reads out the resistance value corresponding to the bus bar 14 and the electrical wiring 15 from the storage means 25. Next, the temperature T of the battery module 11 or 12 is acquired by receiving the detection signal St from the temperature detection unit 24. Then, the resistance value R (T) of the bus bar 14 and the electrical wiring 15 at the temperature T is calculated as R (T) = R (T0) × {1 + α × (T−T0)}, where α is the specific heat coefficient of each resistance. To do.

  Further, the voltage drop amount calculation means 26 acquires the current value I of the charge / discharge current flowing through the assembled battery 10 from the current detection means 23. Then, a voltage drop amount in the resistance is calculated as a product of the resistance value R (T) corresponding to the battery cell 13 and the current value I (R (T) × I).

  The correction unit 27 acquires the output voltage of the battery cell 13 detected as the voltage difference between the connection positions P from the voltage detection unit 21, and further calculates the voltage drop amount in the bus bar 14 and the electrical wiring 15 as the voltage drop amount calculation unit 26. Get from. Then, the detected value of the output voltage is corrected by adding the voltage drop amount to the detected value of the output voltage, and the result is output as the detection signal Sv.

  The control means 30 receives the detection signals Sv, Sa, St, acquires the voltage value of the output voltage of each battery cell 13 constituting the assembled battery 10, the current value of the charge / discharge current, and the temperature, and acquires the acquired voltage. The charging / discharging of the assembled battery 10 is controlled based on the value, the current value, and the temperature.

  FIG. 7 shows a flowchart of voltage detection processing for detecting the output voltage of the battery cell 13. This voltage detection process is performed by the voltage detection device 20 at a predetermined cycle.

  In step S <b> 10, the battery cell 13 that is the detection target of the output voltage is selected. In step S11, the output voltage of the selected battery cell 13 is detected.

  In step S12, the types of the bus bar 14 and the electrical wiring 15 corresponding to the battery cell 13 selected in step S11 are read from the storage means 25. For example, if the battery cell 13 selected in step S11 is the battery cell C1, the type of the bus bar 14 and the electrical wiring 15 corresponding to the battery cell C1 is the cell connection bus bar 14a in the cell row. In step S13, the resistance value corresponding to the read type of resistance is read from the storage means 25. In step S14, the temperature of the battery cell 13 is acquired from the output signals of the thermistors T1 and T2. In step S15, the resistance value at the current temperature is calculated based on the resistance value at the reference temperature and the temperature of the battery cell 13.

  In step S16, the current value of the charge / discharge current flowing through the assembled battery 10 is acquired from the output signal from the Hall element. In step S17, a voltage drop amount is calculated as the product of the resistance value calculated in step S15 and the current value detected in step S16. In step S18, the output voltage of the battery cell 13 is corrected by adding the amount of voltage drop to the output voltage of the battery cell 13, and the process ends.

  The effects achieved by this embodiment will be described below.

  The output voltage of the battery cell 13 can be accurately calculated by correcting the output voltage of the battery cell 13 using the voltage drop amount due to the bus bar 14 and the electric wiring 15. Thereby, charging / discharging control of the battery cell 13 can be performed suitably, and eventually charging / discharging control of the assembled battery 10 can be performed suitably.

  The conductive members such as the bus bar 14 and the electric wiring 15 have a plurality of forms that are different in at least one of shape, size, and material. When the conductive member has the same form, the conductive member has the same resistance value. Therefore, the storage means 25 stores resistance values for each form of the bus bar 14 and the electrical wiring 15. Thereby, the number of resistance values memorize | stored in the memory | storage means 25 can be reduced.

  The resistance values of the bus bar 14 and the electric wiring 15 change depending on the temperature. Therefore, by detecting the temperature of the battery cell 13 and calculating the resistance value of the bus bar 14 and the electrical wiring 15 using the temperature, the voltage drop amount due to the resistance of the bus bar 14 and the electrical wiring 15 can be accurately calculated. Can do.

(Other embodiments)
-In the assembled battery with which a battery system is provided, each unit battery may be comprised by the some battery cell. The configuration is shown in FIG. The assembled battery 40 shown in FIG. 8 includes two battery modules 41 and 42, and each of the battery modules 41 and 42 includes 12 battery cells 44. The battery cells Ca <b> 1 to Ca <b> 3, Cb <b> 1 to Cb <b> 3, Cc <b> 1 to Cc <b> 3, and Cd <b> 1 to Cd <b> 3 included in the battery module 41 constitute a unit battery 43 by connecting three battery cells 44 in parallel by the bus bar 14. . The unit batteries 43 are connected in series by the bus bar 14.

  Even when the assembled battery included in the battery system is the assembled battery 40 illustrated in FIG. 8, by using the resistance value between the terminal of the unit battery 43 and the connection position P included in the bus bar 14, the voltage based on the resistance value is used. The amount of drop can be calculated and the output voltage of the unit battery 43 can be corrected.

  In the above embodiment, the connection position P for connecting the voltage detection means 21 to the bus bar 14 is the position closer to the positive electrode of the battery cell 13, but the connection position P may be provided at the center of the bus bar 14, for example.

  Instead of detecting the temperature of the battery modules 11 and 12 by the thermistors T1 and T2, the temperature of the assembled battery 10 may be acquired based on the current value I of the charge / discharge current flowing through the assembled battery 10. Specifically, in the battery cell 13, the bus bar 14 and the electric wiring 15 based on the current value I of the charge / discharge current flowing through the assembled battery 10 and the internal resistance of the battery cell 13 and the resistance values of the bus bar 14 and the electric wiring 15. The generated Joule heat may be calculated, and the temperature of the assembled battery 10 may be acquired based on the Joule heat.

  -Connection with the battery modules 11 and 12 may replace the connection by the electrical wiring 15, and may join the bus bars 14 directly.

  The resistance value stored in the storage unit 25 may be calculated by the following method. The internal resistance value of each battery cell 13 is acquired in advance. Then, after the battery cell 13, the bus bar 14, and the electric wiring 15 are combined to complete the assembled battery 10, the resistance value between the connection positions P is detected. By subtracting the internal resistance value of the battery cell 13 from the detected resistance value between the connection positions P, the resistance values of the bus bar 14 and the electrical wiring 15 can be calculated. By calculating the resistance value of the bus bar 14 and the electrical wiring 15 by this method, the variation of the resistance value due to the contact between the bus bar 14 and the electrical wiring 15 and the battery cell 13 and the individual difference of the bus bar 14 and the electrical wiring 15 is taken into consideration. The amount of voltage drop can be calculated, and the output voltage of the battery cell 13 can be calculated more accurately.

DESCRIPTION OF SYMBOLS 10,40 ... Assembly battery, 13 ... Battery cell (unit battery), 43 ... Unit battery, 14 ... Bus bar (conductive member), 15 ... Electric wiring (conductive member), 21 ... Voltage detection means, 26 ... Voltage drop amount calculation Means 27: Correction means.

Claims (5)

A plurality of unit cells (13, 43) are provided, the unit cells are arranged next to each other, and a conductive member (14, 15) is connected to the positive electrode side and the negative electrode side of each unit cell. An assembled battery (10, 40) in which the unit cells are connected in series by electrically connecting the electrodes of the adjacent unit cells by
Voltage detection means (21) for detecting an output voltage for each unit cell based on a voltage difference between the conductive member on the positive electrode side and the negative electrode side of the unit cell;
Voltage drop amount calculating means (26) for calculating a voltage drop amount due to the resistance of the conductive member for each unit battery;
Correction means (27) for correcting the output voltage of the unit battery detected by the voltage detection means by the voltage drop amount calculated by the voltage drop amount calculation means;
Temperature acquisition means (24) for acquiring the temperature of the assembled battery;
With
The voltage drop amount calculating means calculates a voltage drop amount due to a resistance component of the conductive member for each unit battery based on the temperature of the assembled battery acquired by the temperature acquisition means. . A storage means (25) for storing the resistance value of each unit battery with respect to the resistance of the conductive member between the positive electrode side and the negative electrode side connection position (P) to which the voltage detection means is connected,
The voltage drop amount calculating means reads a resistance value of the resistance of the conductive member for each unit cell from the storage means, and calculates a voltage drop amount due to the resistance of the conductive member based on the resistance value. The battery system according to claim 1, characterized in that: The conductive member is provided in a plurality in the assembled battery, and has a plurality of forms in which at least one of shape, size and material is different,
The storage means stores a resistance value for each form of the conductive member,
The voltage drop amount calculation means reads the resistance value of the corresponding conductive member for each unit battery from the storage means, and calculates the voltage drop amount for each unit battery based on the read resistance value. The battery system according to claim 2. The assembled battery includes a plurality of battery modules (11, 12) including a plurality of the unit batteries, and each unit battery of the plurality of battery modules is electrically connected to each other by the conductive member. ,
As the conductive member, a first conductive member (14a) used in a part for electrically connecting the unit cells in the battery module, and a second conductive member (14c) serving as a positive electrode output terminal in the battery module, A third conductive member (14d) serving as a negative electrode output terminal in the battery module, and a fourth conductive member (15) electrically connecting the battery modules by the positive electrode output terminal and the negative electrode output terminal. Have
4. The battery system according to claim 2, wherein a resistance value of each of the first to fourth conductive members is stored in the storage unit. 5. Current detection means (23) for detecting a current value of a charge / discharge current flowing in the assembled battery;
The temperature acquisition means calculates the amount of heat generated in the assembled battery based on the current value of the charge / discharge current of the assembled battery detected by the current detection means, and acquires the temperature of the assembled battery based on the amount of generated heat. The battery system according to any one of claims 1 to 4, wherein:

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