JP2007037227A - Control circuit of battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a control circuit of a battery pack for automatically removing an oxide film and preventing a formation of the oxide film. <P>SOLUTION: The quantity of a self discharge in a cell is found from a difference between a cell voltage when a vehicle stops or a bypass circuit is turned off and a cell voltage when the vehicle is activated. A relationship between the quantity of the self discharge and an uncontrolled duration of the cell is previously acquired. A stop duration of the vehicle is found from the relationship and the quantity of the self discharge. When an integral value of the stop duration exceeds a predetermined time, a current is forcibly carried to the bypass circuit. The oxide film is removed, or prevented from being formed. In the battery pack having a plurality of batteries (cells) connected in series, the problems that the current is not carried to a bypass resistor, the oxide film is formed at a terminal for detecting the voltage of the cell to which the current is not carried for a long time and a characteristic of the cell can not be accurately controlled are overcome when a fluctuation in capacities between the cell having a lower voltage is adjusted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control circuit for managing a state of charge (hereinafter abbreviated as SOC) in a battery pack composed of a plurality of single cells.

  In an assembled battery in which a plurality of single cells (hereinafter abbreviated as cells) are connected in series, each cell has a cell voltage detection terminal for voltage detection. A voltage detection means for detecting the voltage of each cell and a discharge resistor (bypass circuit) for flowing a discharge current from each cell are connected in parallel. Furthermore, based on the battery voltage detected by each of the voltage detection means described above, the current from the cell is supplied to each discharge resistor to appropriately discharge the cell power, thereby correcting cell capacity variations among multiple cells. An assembled battery control circuit is disclosed in the following “Patent Document 1”.

  In such an assembled battery control circuit, for example, the voltage of the cell having the lowest voltage (hereinafter referred to as the lowest voltage) among a plurality of cells is detected, and the power of the cells other than the lowest voltage is determined using this lowest voltage as the target voltage. Which discharges through a discharge resistor and adjusts the variation in cell capacity of a plurality of cells (Patent Document 2 below), or discharges the power of the cell with the highest voltage through the discharge resistor to vary the cell capacity A control circuit of an assembled battery (Patent Document 3 below) that adjusts the power is disclosed.

By the way, in such an assembled battery control circuit, when there is a cell that always has the lowest voltage due to, for example, deterioration of the battery or variation in characteristics, a current is not supplied to the discharge resistance connected to the cell. Does not flow, an oxide film is generated at the cell voltage detection terminal, and the voltage detection means cannot accurately detect the cell voltage, or the discharge current from the cell to the discharge resistor is reduced.
JP 2002-343171 A JP 2002-10512 A JP 2002-354684 A

  As described above, in the conventional assembled battery charge control device, when there is a cell that always has the lowest voltage, current hardly flows even when charging to this cell, and therefore an oxide film is formed at the cell voltage detection terminal. As a result, the accuracy of voltage measurement is reduced, or the discharge current is reduced during discharge. In addition, in order to prevent this oxide film formation, there may be a method in which each terminal of the cell is plated with gold. However, in a hybrid vehicle equipped with an internal combustion engine and an electric motor as a prime mover, the number of cells is large and all of the terminals are Applying gold plating to the metal is a problem in terms of cost increase.

  Therefore, an object of the present invention is to provide a control circuit for an assembled battery that prevents an oxide film from being generated at a cell voltage detection terminal of a specific cell in the assembled battery.

  In order to achieve the above object, in the present invention, voltage correction means connected to each cell to detect the voltage of each cell and select each cell in order to correct and arrange the capacity variation of each cell in the assembled battery. A bypass circuit through which a discharge current from each cell flows, and a connection between the bypass circuit and each cell based on the voltage value detected by the voltage detection means to control a current flowing through the bypass circuit. Using a circuit configuration having a cell controller CPU to control, the elapsed time from the time when the connection with the bypass circuit of the cell is finally turned off for each cell is longer than a preset time between the cell and the bypass circuit. When the state where the connection is not turned on continues, the circuit configuration is such that the discharge current is forced to flow through the bypass circuit of the cell.

  According to the present invention, when the oxide film is formed or may be formed on the battery terminal without being energized for a long time, the process of automatically removing the oxide film or suppressing the formation of the oxide film is performed by software. It can be easily implemented by changing the cost, and it can be realized with a simple structure while suppressing an increase in cost.

(Embodiment 1)
FIG. 1 shows a block diagram of a control circuit for an assembled battery used in the present invention. The electric power of the assembled battery 1 composed of cells (cells) C1 to Cn is supplied to the vehicle load 2. Cell controllers 41 to 4n are connected to the cell voltage detection terminals 3 of the respective cells. In each of the cells C1 to Cn, a bypass circuit 5 constituted by a cell discharge resistor and a voltage detection means 6 are connected in parallel. The voltage value detected by the voltage detection means 6 is input to the cell controller CPU (processing device) 7, and the cell controller CPU 7 bypasses if the input voltage value is lower than the preset voltage value for a long time. The cell 5 is forcibly discharged through connection between the circuit 5 and the cell (bypass circuit is turned on), and the oxide film countermeasure process for the cell voltage detection terminal 3 is performed. The operation of the cell controller CPU 7 is controlled by the main CPU 8.

  Hereinafter, the contents of processing in the cell controllers 41 to 4n will be specifically described with the cell controller 41 as an example. In FIG. 1, it is assumed that a state in which no current flows in the bypass circuit 5 of the cell controller 41 continues because the cell voltage of the cell C1 is the lowest among the cells C1 to Cn. While this state continues, the cell controller CPU 7 uses the “cell voltage (V1) at the time of previous vehicle stop” and “cell voltage (V2) at the time of starting this time” measured by the voltage detection means 6, The self-discharge amount ΔV of the battery can be obtained by the following equation.

V1-V2 = ΔV (1)
Here, although not shown in the figure, the relationship of the “self-discharge amount with respect to the leaving period” for each of the cells C1 to Cn is measured and mapped in advance and registered in the cell controller 7 or the main CPU 8. From the self-discharge amount ΔV obtained by the equation (1) and the data of this map, the “time during which the vehicle is stopped” can be obtained by the cell controller CPU 7. On the other hand, the main CPU 8 records the “time during which the vehicle has been started” every time and sends it to the cell controller CPU 7. In the cell controller CPU 7, the “time during which the vehicle has been stopped” previously obtained by the cell controller CPU 7 and the “time during which the vehicle has been started” received from the main CPU 8 are respectively integrated, and the bypass circuit 5. Estimate the total vehicle stop time before the last vehicle start-up and the last time the bypass current flowed, and the total time when the connection between the bypass circuit and the cell was disconnected (bypass circuit off) When the predetermined time is exceeded, the bypass circuit 5 is turned on and a bypass current is forced to flow through the cell voltage detection terminal 3 to remove the oxide film and prevent the generation of the oxide film.

  That is, in the present invention, when the time elapsed since the time when the bypass circuit 5 of the cell for each cell was last turned off is continued for a preset time or longer, the bypass circuit 5 is not turned on. The cell voltage detection terminal 3 is provided with an oxide film countermeasure by forcibly turning on the bypass circuit 5 of the cell and allowing a bypass current to flow. FIG. 2 is a flowchart showing this processing procedure.

First, voltage detection of the cells C1 to Cn constituting the assembled battery 1 is performed by the voltage detection means 6 mounted on the cell controllers 41 to 4n (step S01). After detecting the cell voltage, the calculation of the equation (1) is executed to calculate the self-discharge amount ΔV of the cell (step S02). From this self-discharge amount ΔV and the mapped data of “self-discharge amount with respect to vehicle leaving time”, the time during which the vehicle has been stopped is obtained (step S03). Subsequently, the time when the vehicle was last activated is received from the main CPU 8 (step S04). Then, in the last vehicle start earlier, the elapsed time T ₁ of the bypass circuit 5 finally off until the last vehicle start, obtained in the step S03 and "time had stopped the vehicle T _2" obtains the sum of the three parties of the time T _3, which has been started last vehicle, including previously last, finally the bypass circuit 5 to turn off determining the elapsed time T ₄ which has not been energized cell C1 from ( Step S05).

Then, the cell voltage detection time T ₅ the oxide film is estimated to be formed if no current to terminal 3, compares the time T ₄ did not energized the electrode, the non-energized time T ₄ is the when greater than the time T _5, i.e., to reach the time that might oxide film is formed (step S06 / YES), the bypass circuit 5 is turned on (step S07), the bypass circuit 5 is turned on Is measured (step S08). The measured time is determined whether a predetermined time has elapsed T ₆ that is set for preventing oxidation film removal or oxide film formation. If the predetermined time has elapsed (step S09 / YES), the bypass circuit 5 is turned off (step S10), and the normal control is resumed (step S11). If the predetermined time has not elapsed (step S09 / NO), the process returns to step S08 and the time measurement is continued until the predetermined time is reached. The above-mentioned non-energization time T ₄ is, if not reached the time T ₅ the oxide film on the cell voltage detection terminal 3 is presumed to form (step S06 / NO), remove the bypass circuit 5, returns to the normal control .

  In this circuit, for example, when the entire electrical system is shut down due to factors such as removing the battery, and the recording of the accumulated time after the bypass circuit 5 is turned off is reset, the vehicle When the activation is started, the bypass circuits 5 of all the cells are forcibly turned on for a predetermined time, and the OFF time of the bypass circuit 5 is measured again from the end of the ON process. As a result, it is possible to prevent the time of the energization process to be performed as a countermeasure against the oxide film from being delayed beyond the time that should be originally performed. When the bypass circuit 4 is turned on and energized, the bypass circuit 5 can be energized when regenerative power that is surplus power other than charging in the vehicle is generated. Thereby, the utilization efficiency of the electric power generated by the vehicle can be improved.

(Embodiment 2)
In the control circuit for an assembled battery according to the first embodiment, each cell is used as a self-discharge amount in the relationship of the mapped “self-discharge amount with respect to vehicle leaving time” for calculating the time during which the vehicle is stopped. The average value of the self-discharge amount obtained every time can also be used. FIG. 3 shows a flowchart in this case. FIG. 3 is obtained by replacing S01 to S03 in FIG. 2 with the processing of S12 to S15. In the second embodiment, the self-discharge amount is obtained for all the cells, the average value thereof is further obtained (S14), and the time during which the vehicle is stopped is calculated using this average value. According to this method, since the amount of self-discharge of each cell can be kept within the deviation from the average value, the variation in the calculated “time during which the vehicle is stopped” can be reduced, and the accuracy can be improved. It is possible to obtain the time during which the vehicle is stopped frequently.

(Embodiment 3)
In the battery pack control circuit according to the first embodiment, an average value of “time when the vehicle is stopped” obtained from the self-discharge amount of each cell voltage is obtained for each cell. It can also be used as “the time during which it was stopped”. FIG. 4 shows a flowchart in this case. In this case, the processing of S01 to S03 in FIG. 2 is replaced with S16 to S19, and the time during which the vehicle is stopped and the average value are obtained in this procedure (S18 and S19). Thereby, the influence by the dispersion | variation in the self-discharge amount for every cell can be suppressed.

(Embodiment 4)
In the assembled battery control circuit according to the first embodiment, the total voltage of the assembled battery can also be used as the cell voltage for obtaining the “time during which the vehicle is stopped”. This method can also suppress the influence of variations in the amount of self-discharge in individual cells.

(Embodiment 5)
The energization for suppressing the formation of the oxide film at the cell voltage detection terminal 6 is performed every time the vehicle is started, that is, the bypass circuit 5 is forcibly energized only for a time set in advance as a sufficient time for the oxide film countermeasure. Is also effective. FIG. 5 shows a flowchart of the processing procedure in this case. In FIG. 5, immediately after the vehicle is started, the bypass circuit 5 is first turned on (S21). Here, measurement of the time during which the bypass circuit 5 is on (energization time) is started (S22). Next, it is determined whether or not this energization time has elapsed in advance (a time sufficient as an oxide film countermeasure). The loop of S23 / NO is circulated until the preset time is reached, and when the preset time is reached (S23 / YES), the bypass circuit is turned off and normal control is entered (S24). By this forced energization process, it is possible to prevent the bypass circuit 5 from being kept off for a long time due to the cell voltage drop, thereby preventing the formation of an oxide film at the cell voltage detection terminal 3.

The block diagram of the control apparatus structure of the assembled battery in this invention. The process flow figure in this invention. FIG. 9 is a flowchart for explaining processing in the second embodiment. FIG. 10 is a flowchart for explaining processing in the third embodiment. FIG. 6 is a flowchart for explaining processing in the fifth embodiment.

Explanation of symbols

1: Main CPU 2: Cell controller CPU 3: Voltage detection means 4: Bypass circuit 5: Cell voltage detection terminal 6: Vehicle load 7: Assembly battery

Claims (8)

In order to correct the capacity variation of each unit cell of the assembled battery formed by connecting the unit cells in series, voltage detection means connected to each unit cell and detecting the voltage of each unit cell, A bypass circuit that is selectively connected to the unit cell and through which a discharge current flows from each unit cell, and controls the connection between the bypass circuit and each unit cell based on the voltage value detected by the voltage detection means; In a control circuit for an assembled battery having a cell controller CPU for controlling a current flowing through the bypass circuit,
For each single cell, the time elapsed since the connection between the single cell and the bypass circuit was last turned off was continued for a preset time or longer and the connection between the single cell and the bypass circuit was not turned on. In the case, the battery pack control circuit is characterized in that a discharge current is forced to flow through the bypass circuit of the unit cell. The assembled battery control circuit according to claim 1,
Data that shows the relationship between the self-discharge amount of the unit cell and the unit cell leaving period is previously stored as a map,
The vehicle is stopped from the difference voltage between the unit cell voltage at the time when the connection between the bypass circuit and the unit cell is finally turned off and the unit cell voltage at the time of starting this time, and the data described in the map. An assembled battery control circuit comprising a calculating means for calculating the time that has been spent. The assembled battery control circuit according to claim 1,
When the record of the elapsed time from the time when the power supply unit is removed and the connection between the bypass circuit and the unit cell before the time is turned off is reset, The connection with the bypass circuit is forcibly turned on for a predetermined time and then turned off again, and the time when the connection between the bypass circuit and the unit cell is turned off is measured again from the end of the off process. A battery pack control circuit. The assembled battery control circuit according to claim 1,
An assembled battery control circuit for forcibly energizing the bypass circuit when regenerative power in a vehicle, that is, surplus power other than charging is charged in the assembled battery. In the assembled battery control circuit according to claim 1 or 2,
An assembled battery control circuit using an average value of self-discharge amounts of all the single cells as a self-discharge amount for calculating the time during which the vehicle is stopped. In the assembled battery control circuit according to claim 1 or 2,
An assembled battery control circuit using an average value of the vehicle stop time calculated from the self-discharge of the cell voltage obtained for each cell as the vehicle stop time. . In the assembled battery control circuit according to claim 1 or 2,
An assembled battery control circuit, wherein a total voltage of the assembled battery is used as the unit cell voltage for obtaining a time during which the vehicle is stopped. The assembled battery control circuit according to any one of claims 1 to 7,
The time for turning on the connection between the bypass circuit and the unit cell and energizing is a predetermined time sufficient for removing the oxide film formed on the voltage detection terminal of the unit cell or suppressing the formation of the oxide film. A battery pack control circuit.

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