JP4232341B2 - Charge control device for battery pack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an assembled battery charge control device.
[0002]
[Prior art]
In general, an assembled battery including a plurality of unit batteries (hereinafter referred to as cells) is used as a battery for driving an electric vehicle. A technique is known in which a battery capacity of each cell is adjusted to be substantially uniform with respect to an assembled battery in which a plurality of cells are connected in series. Since an electric vehicle cannot charge an assembled battery mounted on the vehicle itself, the assembled battery is charged using a charger installed on a stand or the like. When charging an assembled battery, the voltage value of each cell is detected during charging, and when the voltage value of the cell with the highest detected voltage reaches a predetermined charging upper limit voltage, the charging current is gradually decreased to charge the battery. Charging is completed when the current reaches zero.
[0003]
[Problems to be solved by the invention]
The voltage (capacity) of the battery decreases due to natural discharge over time. In particular, when an assembled battery mounted on an electric vehicle is left for a long time, spontaneous discharge occurs in each cell. Since the progress of the natural discharge is different for each cell, the voltage between the cells varies. For this reason, even if the voltage of each cell is made almost uniform during charging, voltage variation occurs between cells when left for a long time. On the other hand, when at least one cell having a low voltage (capacity) is present in the assembled battery, the vehicle performs control to limit battery discharge in order to protect the battery. For this reason, as described above, if there is a cell in which discharge proceeds in the assembled battery, the output of the vehicle may be limited.
[0004]
An object of the present invention is to provide a charge control device that reduces variations in voltage generated between cells even when left for a long period of time.
[0005]
[Means for Solving the Problems]
The present invention will be described with reference to FIGS. 1 and 2 showing one embodiment.
(1) The invention described in claim 1 is applied to a battery pack charge control device including a plurality of unit cells C1 to C40. Then, voltage detection circuits C / C1 to C / C5 that detect voltages of the plurality of unit batteries C1 to C40, respectively, and determination of completion of charging of the assembled battery according to the detection voltages by the voltage detection circuits C / C1 to C / C5 Charging completion determination circuit B / C, variation detection circuit B / C for detecting variations in a plurality of detection voltages detected by voltage detection circuits C / C1 to C / C5, and variation detection circuit B / C. When the charging completion is determined by the variation determination circuit B / C for determining whether the variation exceeds a predetermined value and the charging completion determination circuit B / C, the battery pack is charged by the charging current supplied from the charger. When the variation exceeding the predetermined value is determined by the variation determination circuit B / C after the charging is terminated, the control circuit B / By providing the bets, to achieve the above object.
(2) The invention according to claim 2 further includes voltage adjustment circuits R1 to R8 and TR1 to TR8 for discharging the plurality of unit batteries C1 to C40, respectively, in the battery pack charge control device according to claim 1. The control circuit B / C determines the variation of the detected voltage by the variation determination circuit B / C and before the charging of the assembled battery is finished after the determination of the completion of charging, and the variation exceeding the predetermined value by the variation determination circuit B / C. Is determined, the voltage adjustment circuits R1 to R8 and TR1 to TR8 are instructed to discharge the corresponding unit battery.
(3) The invention according to claim 3 is the battery pack charge control device according to claim 2, wherein the corresponding unit battery is a standard of detection voltage detected by the voltage detection circuits R1 to R8, TR1 to TR8. The unit battery has a deviation exceeding a predetermined value. (4) The invention according to claim 4 is the battery pack charge control device according to any one of claims 1 to 3, wherein the voltage detection circuits C / C1 to C / C5 are assembled by the control circuit B / C. After the charging of the battery is completed, the voltages of the plurality of unit batteries C1 to C40 are detected every predetermined time, and the variation determination circuit B / C has a variation for each of the detected voltages detected every predetermined time. It is characterized by determining whether it exceeds a predetermined value.
[0006]
In the section of means for solving the above problems, the present invention is associated with the drawings of the embodiments for easy understanding. However, the present invention is not limited to the embodiments.
[0007]
【The invention's effect】
The present invention has the following effects.
(1) In the inventions according to claims 1 to 4, the voltage of each unit battery constituting the assembled battery is detected, and the variation in the voltage detected for each unit battery after charging of the assembled battery is predetermined. When the value was exceeded, charging the assembled battery was started again. As a result, even if spontaneous discharge occurs in the unit battery by leaving the assembled battery for a long time after the charging is completed, the assembled battery is charged when the voltage variation of the unit battery exceeds a predetermined value. By increasing the voltage of the unit battery lowered by the above, it is possible to suppress the voltage variation within a predetermined value.
(2) In particular, in the inventions according to claims 2 and 3, a voltage adjustment circuit for discharging the unit battery is provided, and the variation of the voltage of the unit battery exceeds a predetermined value before the charging of the assembled battery is finished. The voltage adjustment circuit is instructed to discharge the unit battery. As a result, the voltage of the unit battery that has risen as a result of charging can be lowered to suppress voltage variations within a predetermined value.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, an example in which the assembled battery is used as a driving battery (power source) for an electric vehicle will be described. However, the present invention is not limited to this. FIG. 1 is an overall configuration diagram of an electric system for driving an electric vehicle according to an embodiment of the present invention. In FIG. 1, 40 cells C1 to C40 are connected in series to constitute an assembled battery. Eight cells C1 to C40 are grouped and connected to cell controllers C / C1, C / C2,..., C / C5, respectively. The five cell controllers C / C1 to C / C5 manage eight cells connected to each other. Here, the number of cells constituting the assembled battery and the number of cell controllers that manage the cells are not limited to the quantities according to the present description.
[0009]
The cell controllers C / C1 to C / C5 detect the voltage of each connected cell and adjust the capacity of each connected cell based on a signal from a battery controller B / C described later. Output a signal. The cell capacity adjustment will be described later.
[0010]
Each of the five cell controllers C / C1 to C / C5 and the battery controller B / C is provided with a communication interface circuit (not shown). The cell controllers C / C1 to C / C5 are managed by the battery controller B / C via this communication interface circuit. The battery controller B / C communicates with each of the cell controllers C / C1 to C / C5 via the communication interface circuit to control each of the cell controllers C / C1 to C / C5. Battery information is received from / C1 to C / C5.
[0011]
The battery information is a voltage value of each cell detected by a voltage detection circuit (not shown) in each cell controller C / C1 to C / C5 when the cell voltage is detected. The received battery information is stored in a memory (not shown) in the battery controller B / C and used for control of the cell controllers C / C1 to C / C5. When the voltage value of the cell is higher than the predetermined voltage range, overcharge occurs, and when the voltage value of the cell is lower than the predetermined voltage range, overdischarge occurs. Thus, the state of charge of the cell can be determined from the voltage value of the cell.
[0012]
The battery controller B / C calculates an average voltage and a standard deviation from the voltage value of each cell and adjusts the capacity of each connected cell for each of the five cell controllers C / C1 to C / C5. Signal for output. Battery controller B / C is managed by controller Cr. The controller Cr controls the inverter Iv that supplies power to the motor M that drives the vehicle and the battery controller B / C based on a command value from an accelerator pedal (not shown).
[0013]
The assembled battery is charged by the charger Cgr. The charger Cgr supplies a charging current to the assembled battery according to a control signal sent from the battery controller B / C. When the battery controller B / C detects the connection of the charger Cgr, the battery controller B / C sends a control signal to the charger Cgr to supply a predetermined charging current from the charger Cgr to the assembled battery. In addition, a command for changing the charging current is sent to the charger Cgr according to the cell voltage received from the cell controllers C / C1 to C / C5.
[0014]
The capacity adjustment circuit is a circuit that suppresses variation in the charging state as a predetermined state (for example, average voltage) by discharging the corresponding cell when the variation in the charging state of the cells C1 to C8 occurs. FIG. 2 is a diagram illustrating a capacity adjustment circuit provided between the cell controller C / C1 and the cells C1 to C8. Here, the cell controller C / C1 will be described as an example, but the other cell controllers C / C2 to C / C5 are the same as the cell controller C / C1. In FIG. 2, a resistor R1 and a transistor TR1 are a capacity adjustment circuit of the cell C1, and the cell C1 is discharged. Resistor R2 and transistor TR2 are a capacity adjustment circuit of cell C2, and discharge cell C2. Hereinafter, similarly, the resistor R8 and the transistor TR8 are the capacity adjustment circuit of the cell C8, and the cell C8 is discharged. The transistors TR1 to TR8 are turned on by an on signal sent from the cell controller C / C1, and turned off by an off signal sent from the cell controller C / C1, respectively. When the transistors TR1 to TR8 are turned on, the cells C1 to C8 are discharged through the corresponding resistors R1 to R8. The cell controller C / C1 turns on and discharges the transistor corresponding to the cell for which the variation in the charging state is determined from the voltage detection data described above.
[0015]
A flow of processing performed by the battery controller B / C will be described with reference to a flowchart. The process according to the flowcharts of FIGS. 3 and 4 is started by detecting the ignition off of the vehicle. In step S1 of FIG. 3, the battery controller B / C determines whether or not the charger Cgr is connected. When the connection of the charger Cgr is detected, an affirmative determination is made in step S1 and the process proceeds to step S2. When the connection of the charger Cgr is not detected, a negative determination is made in step S1 and the determination process is repeated.
[0016]
In step S2, the battery controller B / C starts charging the assembled battery by supplying a predetermined charging current from the charger Cgr to the assembled battery, and proceeds to step S3. In step S3, the battery controller B / C causes the cell controllers C / C1 to C / C5 to detect each cell voltage, and receives the detected cell voltage values from the cell controllers C / C1 to C / C5. Store in memory. In step S4, the battery controller B / C determines whether or not the voltage value of the cell having the maximum voltage among the cells has reached a predetermined stop voltage. If the stop voltage has been reached, an affirmative determination is made in step S4 and the process proceeds to step S5. If the stop voltage has not been reached, a negative determination is made in step S4 and the process returns to step S2.
[0017]
FIG. 5A is a diagram showing the relationship between the charging time and the charging current of the assembled battery. In FIG. 5 (a), the horizontal axis represents the charging time, and the vertical axis represents the charging current. A point A in FIG. 5A represents a state from the start of charging until the voltage value of the cell having the maximum voltage reaches the stop voltage. FIG. 5B shows the detection voltage for each cell constituting the assembled battery at the point A. In FIG. 5 (b), the horizontal axis is the cell number, and the vertical axis is the detected voltage value. In step S4, the battery controller B / C monitors the voltage value of the cell having the maximum voltage.
[0018]
When the battery controller B / C determines that the maximum cell voltage has reached the charge stop voltage at the point of time t51 in FIG. 5A, the battery controller B / C sets the charging current to 1 in step S5 in FIG. The level is lowered and the process proceeds to step S6. The amount of change in the charging current is determined in advance by the charging sequence. In step S6, the battery controller B / C causes the cell controllers C / C1 to C / C5 to detect each cell voltage, and receives the detected cell voltage values from the cell controllers C / C1 to C / C5. Store in memory.
[0019]
In step S7, the battery controller B / C determines a charge stop voltage corresponding to the charge current reduced by one level, and determines whether or not the voltage value of the cell having the maximum voltage among the cells has reached the charge stop voltage. To do. When the stop voltage is reached, step S7 is affirmed and the process proceeds to step S8. When the stop voltage is not reached, step S7 is negatively determined and the process returns to step S6.
[0020]
When the battery controller B / C determines that the maximum cell voltage has reached the charge stop voltage at the point of timing t52 in FIG. 5 (a), the battery controller B / C has the charge current at step S8 in FIG. It is determined whether it is the minimum value. If the charging current is the minimum value, an affirmative determination is made in step S8 and the process proceeds to step S9. If the charging current is not the minimum value, a negative determination is made in step S8 and the process returns to step S5. When the battery controller B / C makes a negative determination in step S8, the charging current is further reduced by one step, and the charging current is gradually reduced by determining the charging stop voltage corresponding to the new charging current, thereby charging the assembled battery. Continue.
[0021]
When the battery controller B / C determines that the maximum cell voltage has reached the charge stop voltage at the point of time t53 in FIG. 5A, the battery controller B / C makes a positive determination in step S8 of FIG. Proceed to S9. In step S9, the battery controller B / C causes the cell controllers C / C1 to C / C5 to detect each cell voltage again, and receives the detected cell voltage values from the cell controllers C / C1 to C / C5. To store in memory. In step S10, the battery controller B / C calculates the average voltage value of all the cells based on each detected cell voltage value, and proceeds to step S11.
[0022]
In step S11, the battery controller B / C calculates the standard deviation of the cell voltage value based on each cell voltage value and the average voltage value, and proceeds to step S12. In step S12, the battery controller B / C determines whether or not the standard deviation is equal to or less than a predetermined value. The standard deviation represents the cell voltage variation. For example, if the standard deviation is 0.002 (V) or less, step S12 is affirmed and the process proceeds to step S14 in FIG. 4, and if the standard deviation exceeds 0.002 (V), step S12 is negatively determined. Proceed to step S13.
[0023]
In step S13, the battery controller B / C sets the charge current to 0 (A) and the capacity adjustment circuit corresponding to the cell controller connected to the cell controller having a large variation with respect to the average voltage value. A control signal for turning on the transistor is output. As a result, the capacity of the cell is adjusted. The time for which the transistor is turned on is calculated by the battery controller B / C according to the variation, and a control signal related to the on time is output from the battery controller B / C to the cell controller. Battery controller B / C will return to step S9, if capacity adjustment is performed, and will repeat the process from step S9 to step S13 until a standard deviation becomes below a predetermined value.
[0024]
In step S14 of FIG. 4, the battery controller B / C completes charging / discharging of the assembled battery, and proceeds to step S15. In step S15, the battery controller B / C determines whether or not the time elapsed after completion of charging / discharging or after checking the cell voltage variation by the processing from step S17 to step S20 described later is equal to or longer than a predetermined time. To do. For example, if 30 minutes or more have elapsed, the determination in step S15 is affirmative and the process proceeds to step S17. If less than 30 minutes, the determination in step S15 is negative and the process proceeds to step S16. In step S16, the battery controller B / C determines whether or not the charger Cgr is disconnected. If the disconnection of the charger Cgr is detected, an affirmative determination is made in step S16 and the process of FIG. 4 is terminated. If the disconnection of the charger Cgr is not detected, a negative determination is made in step S16 and the process returns to step S15.
[0025]
In step S17, the battery controller B / C causes the cell controllers C / C1 to C / C5 to detect each cell voltage again, and receives the detected cell voltage values from the cell controllers C / C1 to C / C5. To store in memory. In step S18, the battery controller B / C calculates the average voltage value of all the cells based on each detected cell voltage value, and proceeds to step S19.
[0026]
In step S19, the battery controller B / C calculates the standard deviation of the cell voltage value based on each cell voltage value and the average voltage value, and proceeds to step S20. In step S20, the battery controller B / C determines whether or not the standard deviation is equal to or less than a predetermined value. For example, if the standard deviation is 0.002 (V) or less, the determination in step S12 is affirmative and the process returns to step S15. If the standard deviation exceeds 0.002 (V), the determination in step S20 is negative, and FIG. Return to step S2 and repeat charging.
[0027]
The embodiment described above will be summarized. The cell controller C / C1 to C / C5 detects the voltage of each cell constituting the assembled battery every 30 minutes after the completion of charging / discharging of the assembled battery, and the standard deviation of the cell voltage is 0.002 (V). Since charging / discharging is repeated again when exceeding the above (negative determination in step S20), after the charging / discharging is completed (step S14), the voltage reduced by the natural discharge generated in each cell is increased by charging, The variation of can be suppressed. Further, even when the battery voltage decreases due to a load such as a DC / DC converter connected to the assembled battery, the battery voltage can be increased to a predetermined charge stop voltage by starting charging again.
[0028]
In the above description, an electric vehicle has been described as an example. However, the present invention can also be provided to a hybrid vehicle (HEV) equipped with an engine and a motor.
[0029]
The battery controller B / C determines that the variation in the cell voltage is large when the standard deviation of the detected cell voltage exceeds 0.002 (V), but the standard deviation value described above was used for the explanation. It does not have to be a value.
[0030]
Further, the battery controller B / C completes charging / discharging of the assembled battery (step S15), or when 30 minutes have elapsed after the standard deviation is determined to be 0.002 (V) or less (positive determination in step S20). The voltage of each cell of the assembled battery is detected to check the voltage variation (step S17 to step S20). However, the interval for performing such a diagnosis does not have to be every 30 minutes as described above. It may be performed every hour.
[0031]
In the above description, after charging the assembled battery, that is, after affirmative determination is made in step S8 with the charging current at the minimum value, the cell voltage variation is checked to discharge cells having a large variation with respect to the average voltage value. Then, the capacity was adjusted (step S13), and when the variation was equal to or less than a predetermined value, it was considered that the charging was completed (step S14). Instead of this, if an affirmative determination is made in step S8, it may be considered that the charging is completed (step S14).
[0032]
The correspondence between each component in the claims and each component in the embodiment of the invention will be described. The cells C1 to C40 are unit batteries, the cell controllers C / C1 to C / C5 are voltage detection circuits, The battery controller B / C corresponds to the charge completion determination circuit, the variation detection circuit, the variation determination circuit, and the control circuit, and the capacity adjustment circuit (resistors R1 to R8 and transistors TR1 to TR8) corresponds to the voltage adjustment circuit.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an electric system for driving an electric vehicle according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a capacity adjustment circuit.
FIG. 3 is a flowchart illustrating a flow of processing performed by a battery controller during charging.
FIG. 4 is a flowchart illustrating a flow of processing performed by a battery controller during charging.
5A is a diagram showing a relationship between charging time and charging current, and FIGS. 5B and 5C are diagrams showing voltages for each cell constituting the assembled battery. FIG.
[Explanation of symbols]
B / C ... battery controller, C1-C40 ... cell,
C / C1 to C / C5 ... cell controller,
Cgr ... charger, R1-R8 ... resistor,
TR1 to TR8 ... transistor

Claims (4)

In a battery pack charge control device composed of a plurality of unit batteries,
A voltage detection circuit for detecting a voltage of each of the plurality of unit cells;
A charging completion determination circuit that determines completion of charging of the assembled battery according to a detection voltage by the voltage detection circuit;
A variation detection circuit for detecting variations in the plurality of detection voltages detected by the voltage detection circuit;
A variation determination circuit for determining whether or not the variation detected by the variation detection circuit exceeds a predetermined value;
When the completion of charging is determined by the charging completion determination circuit, the charging of the assembled battery by the charging current supplied from the charger is terminated, and the variation exceeding a predetermined value by the variation determination circuit after the charging is terminated. And a control circuit that starts charging the assembled battery again when the battery pack is determined. In the assembled battery charge control device according to claim 1,
A voltage adjusting circuit for discharging each of the plurality of unit cells;
The control circuit determines a variation in the detection voltage by the variation determination circuit before ending charging of the assembled battery after determining the completion of charging, and when the variation determination circuit determines a variation exceeding a predetermined value, A battery pack charge control device that instructs a voltage adjustment circuit to discharge a corresponding unit battery. In the assembled battery charge control device according to claim 2,
The relevant unit battery is a unit battery in which a standard deviation of a detection voltage detected by the voltage detection circuit exceeds a predetermined value. In the assembled battery charge control device according to any one of claims 1 to 3,
The voltage detection circuit detects the voltage of each of the plurality of unit cells every predetermined time after the charging to the assembled battery is finished by the control circuit,
The assembled battery charge control device, wherein the variation determination circuit determines whether or not the variation exceeds a predetermined value for each of the detected voltages detected every predetermined time.

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