JP6988436B2 - Battery control device - Google Patents

Description

The present invention relates to a battery control device.

In a power supply system using a storage battery in which a plurality of battery cells are connected in series, a voltage detection circuit for detecting the voltage of each battery cell and a voltage of each battery cell detected by the voltage detection circuit are equalized. A equalization circuit for this is provided. A low-pass filter circuit for removing noise included in the voltage input to the voltage detection circuit from the battery cell is provided between the voltage detection circuit and each battery cell. Then, the voltage of each battery cell is detected by measuring the voltage of the capacitor of this low-pass filter circuit. However, when discharging from each battery cell by the equalization circuit, the voltage of the capacitor fluctuates due to the voltage drop due to the contact resistance included in the path between the battery cell and the filter circuit, so the voltage is applied by the voltage detection circuit. It contributes to the error in detection. Therefore, in the technique of Patent Document 1, a configuration is disclosed in which a voltage is detected three times and the voltage detected three times is substituted into a predetermined formula to calculate the value of the battery cell after discharging by the equalization circuit. Has been done.

Japanese Unexamined Patent Publication No. 2014-81268

However, in the configuration of Patent Document 1, the voltage is detected three times with a predetermined time interval, and a waiting time for detection is required. Therefore, an extra time for the standby time is required to obtain the voltage of the battery cell, and further improvement has been desired.

The present invention has been made in view of the above problems, and a main object thereof is to provide a battery control device capable of quickly and more accurately detecting the voltage of a battery cell.

In the first means, a filter circuit (31) having a storage battery (10) in which a plurality of battery cells (C) are connected in series and a capacitor (33) provided for each battery cell and connected to the battery cell. A connecting member (L) connecting between the battery cell and the filter circuit, and a discharge switch (22) provided for each battery cell and connected in series to the battery cell via the connecting member. ) And a battery control device (20) applied to a power supply system including a discharge circuit (34) including a discharge resistance (35), which is provided for each battery cell and has noise removed by the filter circuit. Discharge determination for determining the necessity of discharge in the discharge circuit for each battery cell based on the voltage detection unit (21) that detects the voltage of the battery cell and the voltage of the battery cell detected by the voltage detection unit. Switch control that opens and closes the discharge switch of the battery cell that is determined to require discharge by the discharge determination unit a plurality of times between the detection timing at which the voltage is detected by the voltage detection unit and the detection timing. It has a part and.

The internal resistance and connection resistance of the connection member between each battery cell and the filter circuit changes due to deterioration over time, etc., and when a current for discharge is passed through the discharge circuit, the voltage drop due to the resistance at the connection member causes the connection member. The voltage of the capacitor fluctuates. Therefore, the voltage detected by the voltage detection unit after the noise is removed by the filter circuit is different from the voltage of the battery cell, which causes an error in the voltage of the battery cell. In addition, since the resistance value changes due to deterioration over time, it is difficult to calculate the measurement error in advance based on the difference between the voltage of the capacitor after equalization and the voltage of the battery cell.

In this means, the discharge switch is opened and closed between the detection timing and the detection timing of the voltage detection unit for the battery cell determined to be discharged by the discharge determination unit. When the discharge switch is closed, even if the capacitor is discharged due to a voltage drop at the connecting member, the discharge switch is opened and the capacitor tries to return to the voltage of the battery cell. By repeating these behaviors between the detection timings, the voltage error between the capacitor and the battery cell is reduced compared to the case where the discharge switch is kept closed between the detection timings. be able to. Therefore, it is possible to suppress the discharge of the capacitor due to the voltage drop in the connecting member, shorten the time to wait for the voltage of the capacitor to recover, and detect the voltage value of the battery cell with a small error without making any special correction. can.

The second means includes an abnormality detection unit that detects an abnormality in the power supply system between the detection timing at which the voltage is detected by the voltage detection unit and the detection timing, and the abnormality detection unit detects an abnormality. During the detection, the switch control unit opens and closes the discharge switch of the battery cell that needs to be discharged by the discharge determination unit, and discharges the battery in the discharge circuit.

When the discharge switch is opened and closed a plurality of times between the detection timings, the number of times the discharge switch is opened is increased, so that the time for discharging by the discharge circuit is shortened for equalization. Therefore, in this means, in addition to the discharge time originally scheduled for equalization, discharge for equalization is performed while the abnormality detection unit detects an abnormality in the battery system. Therefore, by securing the discharge time in addition to the discharge time for equalization, the necessary discharge for equalization can be performed.

In the third means, the abnormality detecting unit detects the abnormality by causing the switch control unit to close the discharge switch and detecting the result of passing a current through the circuit including the discharge circuit. When the abnormality is detected by the abnormality detection unit, the switch control unit sets the time for closing the discharge switch of the battery cell that needs to be discharged by the discharge determination unit. It is longer than the time for closing the discharge switch of the other battery cells for which discharge is not required in the determination unit.

As the abnormality detection performed by the abnormality detection unit, for example, there is one in which a current is passed through a circuit including a discharge circuit, such as detection of disconnection in a connecting member, and the abnormality is detected based on the result. When such an abnormality is detected, all the battery cells including the battery cells that do not need to be discharged for equalization are discharged. At this time, the discharge time of the battery cell that needs to be discharged by the discharge determination unit is made longer than the discharge time of the other battery cells that the discharge determination unit determines that discharge is unnecessary. While performing the necessary detection in all the battery cells, the battery cells that need to be discharged are discharged for a longer time than the battery cells that do not need to be discharged, so that discharge for equalization is possible.

In the fourth means, the abnormality detecting unit detects the abnormality without causing the switch control unit to close the discharge switch, and the abnormality detecting unit also detects the abnormality. The switch control unit opens and closes the discharge switch of the battery cell that needs to be discharged by the discharge determination unit.

Some of the abnormality detection performed by the abnormality detection unit is to detect an abnormality without using the result of discharging in the discharge circuit, such as measurement of the temperature of a battery cell. Even when such an abnormality is detected, the battery cell that is determined to need to be discharged is discharged for equalization. Therefore, it is possible to increase the time for discharging for equalization.

In the fifth means, the battery cells are divided into a plurality of groups so that the adjacent battery cells are in different groups from each other, and the switch control unit detects the voltage detected by the voltage detection unit. Between the timing and the detection timing, the discharge switch of the battery cell determined to be discharged by the discharge determination unit is continuously opened and closed for each group.

Between the detection timing and the detection timing of the voltage detection unit, the discharge switch is continuously opened and closed for each group for the battery cells that need to be discharged. By continuously opening and closing the discharge switch for each group, while the other groups are discharging, the discharge switch is opened in one group and the time required for the capacitor to return to the voltage of the battery cell is reached. become longer. Therefore, the voltage error between the capacitor and the battery cell can be further reduced, and the voltage value of the battery cell can be quickly calculated with almost no error.

In the sixth means, the battery cells are divided into a plurality of groups so that the adjacent battery cells are in different groups from each other, and the switch control unit detects that the voltage is detected by the voltage detection unit. Between the timing and the detection timing, the discharge switch of the battery cell determined by the discharge determination unit to be discharged is opened and closed a plurality of times with respect to the battery cell of the group.

Between the detection timing and the detection timing of the voltage detection unit, the discharge switch is opened and closed multiple times for a certain group of battery cells that need to be discharged. Discharging each group makes it easier to manage the discharged battery cells.

Schematic block diagram of the power supply system. The flowchart which shows the processing procedure in a battery control device. A flowchart showing a processing procedure of equalization processing. A time chart showing changes in cell voltage during equalization processing. The flowchart which shows the processing procedure of the abnormality determination processing with discharge. A time chart showing the on / off of the discharge switch during the abnormality determination process involving discharge. A time chart showing changes in cell voltage in other embodiments.

Hereinafter, embodiments that embody the battery control device according to the present invention will be described with reference to the drawings. The battery control device according to the present invention is applied to, for example, a power supply system mounted on a hybrid vehicle or an electric vehicle.

As shown in FIG. 1, the power supply system includes a storage battery 10. The storage battery 10 is, for example, a lithium ion storage battery, and serves as a power supply source for an in-vehicle electric load including a traveling motor (not shown) of the vehicle. The lithium ion storage battery is not limited to the lithium ion storage battery, and any storage battery such as a nickel hydrogen storage battery may be used as long as it is a storage battery in which a plurality of unit batteries are connected and supplied at a predetermined voltage.

The storage battery 10 is composed of a battery module 11 in which battery cells C1 to Cn, which are n unit batteries (n is an integer of 1 or more, approximately several to ten and several), are connected in series to each other. The storage battery 10 may be configured by connecting a plurality of battery modules 11 in series or in parallel, or may be configured by one battery module 11. In this embodiment, one battery module 11 is illustrated as an example of the storage battery 10. Further, in the following description, the battery cells C1 to Cn are collectively referred to as a battery cell C. In FIG. 1, the description after the battery cell C1 and the battery cell C9 is omitted.

Each battery module 11 is provided with a monitoring IC 20 that monitors the battery status while calculating the voltage of each battery cell C and performing equalization processing. The monitoring IC 20 is provided with a voltage detection circuit 21 and a discharge switch 22 for each battery cell C. Further, the monitoring IC 20 is provided with a control unit (not shown) for calculating the voltage of each battery cell C, controlling the discharge switch 22, and performing abnormality determination. In this embodiment, the monitoring IC 20 corresponds to the "battery control device", and the voltage detection circuit 21 corresponds to the "voltage detection unit". Further, the monitoring IC 20 may monitor a plurality of battery modules 11 collectively, or may divide one battery module 11 into a plurality of monitoring ICs 20 for monitoring. The control unit may not be provided in the monitoring IC 20, but may be provided in an ECU or the like capable of communicating with the monitoring IC 20.

A voltage detection circuit 21, a filter circuit 31, and a discharge circuit 34 are provided for each battery cell C. Then, connecting members L1 to L (n + 1) connecting the battery cell C and the filter circuit 31 and the discharge circuit 34 are provided. The connecting members L1 to L (n + 1) connect the positive electrode side of each battery cell C to one end of the filter circuit 31, and connect the negative electrode side of each battery cell C to the other end of the filter circuit 31. Further, regarding the connection members L2 to Ln other than the connection members L (n + 1) connected to the connection member L1 on the positive electrode side of the battery cell C1 on the highest voltage side and the negative electrode side of the battery cell Cn on the lowest voltage side, respectively. It is shared between adjacent battery cells C. For example, the connecting member L3 connecting the positive electrode side of the battery cell C3 and one end of the filter circuit 31 is the connecting member L3 connecting the negative electrode side of the battery cell C2 and the other end of the filter circuit 31. In the following description, the connecting members L1 to L (n + 1) are collectively referred to as a connecting member L. In FIG. 1, the description of the connecting member L1 and the connecting member L10 and later is omitted.

The connecting member L includes a wire harness 41 that connects the board B provided with the monitoring IC 20, a filter circuit 31, a discharge circuit 34, and the like and each battery cell C, and a connector 42 that connects the wire harness 41 and the board B. It includes a printed wiring 43 provided on the substrate B and a fuse 44 provided on the printed wiring 43. The wire harness 41 has a resistor 41a generated when a current is passed, and the printed wiring 43 has a resistor 43a generated when a current is passed. Further, the connector 42 has a contact resistance, and the element connected to the printed wiring 43 such as the fuse 44 or the printed wiring 43 has the resistance and the contact resistance of the element itself. The resistance generated when a current is passed through these connecting members L is collectively referred to as an internal resistance R. The magnitude of the internal resistance R varies with aging, ambient temperature, etc., but is generally several hundred mΩ.

The filter circuit 31 removes noise contained in the voltage input to the voltage detection circuit 21 of the monitoring IC 20 from the battery cell C. The filter circuit 31 is a low-pass filter circuit called an RC circuit, and includes a filter resistor 32 and a capacitor 33. The filter resistance 32 has a size of about several kΩ, while the capacitor 33 has a size of several μF. One end of the filter resistor 32 is connected to the connecting member L on the positive electrode side, and the other end is connected to the pin of the monitoring IC 20 connected to the voltage detection circuit 21. One end of the capacitor 33 is connected between the other end of the filter resistor 32 and the voltage detection circuit 21, and the other end of the capacitor 33 is connected to the connection member L on the negative electrode side. The filter circuit 31 may be another filter circuit as long as it is a filter circuit using a capacitor such as a low-pass filter using a coil instead of the filter resistor 32.

The discharge circuit 34 is a circuit for equalizing (balancing processing) the voltage of each battery cell C, and is provided in parallel with the filter circuit 31 for the battery cell C. The discharge circuit 34 includes a discharge switch 22 provided in the monitoring IC 20 and a discharge resistor 35. The size of the discharge resistance 35 is approximately several tens of Ω. One end of the discharge resistor 35 is connected to the connecting member L together with the filter circuit 31, and the other end is connected to a pin of the monitoring IC 20 connected to the discharge switch 22. The discharge resistor 35 is shared between the adjacent battery cells C as well as the connecting member L.

When a current flows through the discharge circuit 34, a current flows from the positive electrode side of the battery cell C to the discharge resistance 35 on the positive electrode side via the connecting member L on the positive electrode side, and a current flows through the discharge resistance 35 on the negative electrode side. The battery cell C returns to the negative electrode side via the connecting member L on the negative electrode side. Then, on this path, specifically, whether or not the discharge switch 22 is provided inside the monitoring IC 20 between the discharge resistance 35 on the positive electrode side and the discharge resistance 35 on the negative electrode side to discharge from the battery cell C. It is controlled by the control unit. The discharge of the battery cell C is divided into a group of odd-numbered battery cells C and a group of even-numbered battery cells C, and the discharge switch 22 is controlled by the control unit so that the discharge is performed at different timings for each group. To. The battery cell C may be discharged at different timings between adjacent battery cells C sharing the connecting member L. For example, the battery cell C may be divided into three groups and discharged. , The battery cell C may be discharged without being divided into groups.

The voltage detection circuit 21 is called an A / D converter and detects the voltage of the capacitor 33. One end of the voltage detection circuit 21 is connected to the filter resistor 32 and the other end is connected to the discharge resistor 35. Since the voltage of each capacitor 33 matches the voltage of each battery cell C connected in parallel in the steady state, each voltage detection circuit 21 detects the voltage of each capacitor 33 by each filter circuit 31. The voltage detection circuit 21 can detect the voltage of each battery cell C in a state where noise is removed. Each voltage detection circuit 21 detects the voltage of each capacitor 33 at a constant cycle.

FIG. 2 is a flowchart performed by the control unit (monitoring IC 20), and this process is performed by the control unit at a predetermined timing. The timing of voltage detection of each battery cell C is scheduled in advance so that it is detected in a fixed cycle, and various abnormality diagnoses are also scheduled in advance so that it is carried out in a predetermined cycle. Then, various abnormality diagnoses are performed between the voltage detection timing and the voltage detection timing of a predetermined cycle, and equalization processing is performed in advance between the voltage detection timing and the voltage detection timing in which the abnormality diagnosis is not performed. It is scheduled.

In step S11, the voltages of all the battery cells C are acquired. Specifically, the voltage detection circuits 21 of all the battery cells C are controlled to acquire the voltage of the capacitor 33, and the voltage detected by the voltage detection circuit 21 is acquired.

In step S12, the battery cell C that needs to be discharged for equalization is set based on the voltage of each battery cell C acquired in step S11. Specifically, when the voltage of a certain battery cell C is higher than the voltage of another battery cell C, it is determined that the battery cell C needs to be discharged for equalization. In the present embodiment, the battery cell C3 and the battery cell C6 will be described below, assuming that discharge for equalization is required.

In step S13, it is determined whether or not the timing of the abnormality diagnosis is scheduled in advance. If it is determined in step S13 that it is not the timing of abnormality diagnosis, equalization processing is performed in step S30. FIG. 3 shows the procedure of equalization processing.

In step S31, the voltages of all the battery cells C are acquired. Specifically, as in step S11, the voltage of the capacitor 33 is detected by the voltage detection circuit 21 for all the battery cells C, and the voltage is acquired.

In step S32, the battery cells C that need to be discharged from the group of odd-numbered battery cells C are discharged. Specifically, in order to discharge in the discharge circuit 34 of the battery cell C3 determined to require discharge, the corresponding discharge switch 22 is turned on (closed state). Then, when a predetermined time (for example, 3 milliseconds) elapses after the discharge switch 22 is turned on, the discharge switch 22 is turned off (open state) and the discharge is terminated.

When the discharge of the odd-numbered battery cell C is completed, in step S33, the battery cell C waits for the switching time. Immediately after issuing the command to turn off the discharge switch 22, there is a possibility that current is still flowing in the discharge circuit 34, so in step S33, it waits for a time for switching (for example, about 1 millisecond). do.

In step S34, the battery cells C that need to be discharged from the group of even-numbered battery cells C are discharged. Specifically, in order to discharge in the discharge circuit 34 of the battery cell C6 that needs to be discharged, the corresponding discharge switch 22 is set to the on state (closed state). Then, when a predetermined time (for example, 3 milliseconds) elapses after the discharge switch 22 is turned on, the discharge switch 22 is turned off (open state) and the discharge is terminated. When the discharge of the even-numbered battery cell C is completed, in step S35, as in step S33, the battery cell C waits for the switching time.

Then, in steps S36 to S38, the odd-numbered battery cells C and the even-numbered battery cells C are discharged in the same manner as in steps S32 to S34. When the discharge of the battery cell C is completed in step S38, the switch is turned off in step S39 to stand by. It waits for, for example, about 1 millisecond until there is no possibility that a current is flowing through the discharge circuit 34.

Here, a time chart when such equalization processing is performed will be described with reference to FIG. FIG. 4 is a diagram showing the voltage of the battery cell C and the voltage of the capacitor 33 (indicated by a broken line) when discharging is performed. In FIG. 4, the horizontal axis represents time and the vertical axis represents the level of each signal. Further, the case where the equalization process is performed twice in succession is shown in this time chart.

First, at the timing t11, the voltage of each battery cell C is detected by the voltage detection circuit 21. Then, when the detection by the voltage detection circuit 21 is completed, the discharge switch 22 of the odd-numbered battery cell C (for example, the battery cell C3) for discharging is turned on (closed state) at the timing t12, and the discharge is performed. Will be carried out.

While discharging in the discharge circuit 34, the voltage of the capacitor 33 changes due to the voltage drop caused by the internal resistance R in the connecting member L. Specifically, in the capacitor 33 corresponding to the battery cell C3 that is discharging, the voltage of the capacitor 33 drops due to the voltage drop in the internal resistance R of the connecting member L3 and the connecting member L4. At this time, the voltage of the capacitor 33 drops due to the relationship determined by the time constant of the filter resistance 32 and the capacitor 33, and the value of the capacitor 33 is the value of the battery cell C3 by the value of the voltage drop due to the internal resistance R of the connecting member L. Decreases against.

After the discharge is performed for a predetermined time (for example, 3 milliseconds), the discharge switch 22 is turned off (open state) at the timing t13. At this time, since the interval between the timing t12 and the timing t13 is short, the voltage of the capacitor 33 drops by the amount of the voltage drop due to the internal resistance R of the connecting member L and starts to recover before becoming steady.

Then, after the discharge switch 22 is turned off, after waiting for a time (for example, about 1 millisecond) for switching until the current does not flow reliably, the even-numbered battery that discharges at the timing t14. The discharge switch 22 of the cell C (for example, the battery cell C6) is turned on (closed) and discharged. Also in the battery cell C6, the voltage of the corresponding capacitor 33 changes as in the case of discharging the battery cell C3. Then, after discharging for a predetermined time (for example, 3 milliseconds), the discharge switch 22 corresponding to the even-numbered battery cell C is turned off (open state) at the timing t15. Between the timing t14 and the timing t15, the voltage of the capacitor 33 corresponding to the discharged battery cell C drops, and at the timing t15, the voltage starts to recover.

On the other hand, the voltage of the capacitor 33 of the odd-numbered battery cell C (for example, the battery cell C3) that was discharged between the timing t12 and the timing t13 is the voltage of the battery cell after the discharge switch 22 is turned off at the timing t13. It rises until it becomes equal to the voltage of C. After the discharge switch 22 is turned off at the timing t13, the voltage of the capacitor 33 gradually rises due to the relationship determined by the time constants of the filter resistor 32 and the capacitor 33. At this time, since the time during which the discharge is performed is short, the difference between the voltages of the capacitor 33 and the battery cell C becomes small, and the voltage recovery becomes easy.

Then, after waiting for a time for switching, at the timing t16, the discharge switch 22 of the battery cell C having an odd number is turned on (closed state) again, and the discharge is performed. After discharging for a predetermined time (for example, 3 milliseconds), the discharge switch 22 corresponding to the odd-numbered battery cell C is turned off (open state) at the timing t17. Then, after waiting for a time for switching, at the timing t18, the discharge switch 22 of the even-numbered battery cell C is turned on (closed state) again, and discharge is performed. After a predetermined time (for example, 1 millisecond) has elapsed, the discharge switch 22 is turned off (open state) at timing t19.

With the switch off, after a predetermined time (for example, 1 millisecond) has elapsed, the next equalization process is performed. At the timing t20, the voltage of each battery cell C is detected by the voltage detection circuit 21. This voltage is the post-discharge voltage after the discharge is performed at the timing t12 to the timing t19. At this time, the voltage of the capacitor 33 of the even-numbered battery cell C that was discharged did not return to the voltage of the battery cell C, but the voltage of the capacitor 33 dropped because the time that was discharged immediately before was short. The amount is also small, and the difference between the capacitor 33 and the battery cell C at the time of voltage detection after discharge is very small as compared with the conventional case. Then, after the timing t21, the discharge is performed in the same manner as after the timing t12.

The discharge switch 22 is opened and closed a plurality of times between the detection timing t11 and the detection timing t20 by the voltage detection circuit 21. Therefore, the discharge circuit 34 discharges the capacitor 33 for a shorter period of time than the capacitor 33 becomes steady, and the voltage error between the capacitor 33 and the battery cell C becomes small. Further, the group of the odd-numbered battery cells C and the group of the even-numbered battery cells C are alternately (consecutively) discharged. Therefore, for example, the voltage of the capacitor 33 corresponding to the even-numbered battery cell C group can be restored while the odd-numbered battery cell C group is being discharged.

Returning to the above description of FIG. 2, when the equalization process is completed, in step S14, the number of times the equalization process is performed is increased by one, and the process proceeds to step S18.

If it is determined in step S13 that it is time to perform the abnormality diagnosis, it is determined in step S15 whether the abnormality diagnosis is an abnormality diagnosis accompanied by discharge in the discharge circuit 34. In the case of an abnormality diagnosis that does not involve discharge, such as temperature measurement of the battery cell C, step S15 is denied, and while the equalization process of step S30 is performed, an abnormality diagnosis that does not involve discharge, such as temperature measurement, is performed in step S16. implement. Then, in step S17, the number of times the equalization process is performed is increased by one, and the process proceeds to step S18. In this way, even during the abnormality diagnosis that does not involve discharge, the equalization process can increase the chances of performing discharge for equalization.

On the other hand, if it is determined in step S15 that the diagnosis is an abnormality accompanied by discharge such as disconnection detection, the discharge abnormality determination process is performed in step S40. In the discharge abnormality determination process, after discharging the odd-numbered battery cell C and determining the abnormality based on the result, the discharge of the even-numbered battery cell C and the abnormality determination based on the result are continuously performed. FIG. 5 shows the procedure of the discharge abnormality determination process.

In step S41, the voltages of all the battery cells C are acquired. Specifically, as in step S11, the voltage of the capacitor 33 in the voltage detection circuit 21 is detected and the voltage is acquired for all the battery cells C.

In step S42, for each of the odd-numbered battery cells C, it is determined in step S12 whether or not the battery cells C are determined to require discharge. In the case of the battery cell C that does not need to be discharged (for example, in the case of the battery cell C5), the discharge circuit 34 discharges the battery cell C for the time required for abnormality determination (for example, 1 to several milliseconds) in step S43. In order to do so, the discharge switch 22 is turned on (closed). Then, when a predetermined time (for example, 1 to several milliseconds) elapses after the discharge switch 22 is turned on, the discharge switch 22 is turned off (open state) and the discharge is terminated.

On the other hand, in the case of the battery cell C that needs to be discharged (for example, in the case of the battery cell C3), in step S44, the discharge switch 22 is turned on (closed state) in order to be discharged by the discharge circuit 34. The time for discharging is longer than the discharging time in step S43, and is about half the time until the next voltage detection timing. Then, when a predetermined time (for example, several milliseconds) elapses after the discharge switch 22 is turned on, the discharge switch 22 is turned off (open state) and the discharge is terminated.

Then, in step S45, the voltages of all the battery cells C are acquired. Specifically, as in step S11, the voltage detection circuit 21 detects the discharged voltage of the capacitor 33 for all the battery cells C, and acquires the voltage. In step S46, based on the voltage detected in step S45, it is determined by a well-known method whether or not the connecting member L has a disconnection.

In steps S47 to S49, the even-numbered battery cells C are discharged in the same manner as in steps S42 to S44 for the odd-numbered battery cells C.

Then, in step S50, the voltages of all the battery cells C are acquired. Specifically, as in step S11, the voltage of the capacitor 33 is detected by the voltage detection circuit 21 for all the battery cells C, and the voltage is received. In step S51, based on the voltage detected in step S50, it is determined by a well-known method whether or not the connecting member L has a disconnection.

Here, a time chart when such a discharge abnormality determination process is performed will be described with reference to FIG. FIG. 6 is a diagram showing an on / off state of the discharge switch 22 of the battery cell C when discharging is performed. In FIG. 6, the horizontal axis represents time and the vertical axis represents the level of each signal.

First, at the timing t41, the voltage of each battery cell C is detected by the voltage detection circuit 21. Then, when the detection by the voltage detection circuit 21 is completed, the discharge switch 22 of the battery cell C having an odd number is turned on (closed state) at the timing t42, and the discharge for the abnormality determination process is performed. Specifically, the discharge switch 22 of the battery cell C having an odd number such as the battery cells C3 and C5 is turned on.

After the discharge is performed for a predetermined time (for example, 1 to several milliseconds), the discharge switch 22 of the battery cell C, which does not require discharge, is turned off (open state) at the timing t43. On the other hand, the battery cell C that needs to be discharged is continuously kept in the on state (closed state). Specifically, the discharge switch 22 of the battery cell C5 that does not require discharge is turned off (open state), while the discharge switch 22 of the battery cell C3 that requires discharge is held in the on state (closed state). ..

When a predetermined time (for example, several milliseconds) elapses from the timing t42 when the discharge switch 22 of the odd-numbered battery cell C is turned on after a further time elapses, the battery cell C requiring discharge is required to be discharged at the timing t44. The discharge switch 22 of the above is also turned off (open state). Specifically, the discharge switch 22 of the battery cell C3 is turned off at the timing t44. The discharge time of the battery cell C that needs to be discharged is preferably longer than twice the discharge time of the battery cell C that does not need to be discharged, and is preferably shorter than half of the detection timing cycle by the voltage detection circuit 21. .. Then, the voltage of the capacitor 33 lowered by the discharge is restored by the timing t45 of the detection by the next voltage detection circuit 21.

At the timing t45, the voltage is detected by the voltage detection circuit 21 for each battery cell C. The disconnection is detected based on the voltage detected at the timing t45. Then, after the timing t46, the even-numbered battery cells C are discharged in the same manner as the odd-numbered battery cells C (similar to the timing t42 and later). Specifically, at the timing t46, the discharge switch 22 of the even-numbered battery cell C is turned on. Then, the discharge switch 22 of the battery cell C4, which does not require discharging, is turned off (open state) at the timing t47. On the other hand, the discharge switch 22 of the battery cell C6, which needs to be discharged, is turned off (open state) at the timing t48.

Then, after the voltage of the capacitor 33 lowered by the discharge is restored, the voltage is detected by the voltage detection circuit 21 for each battery cell C at the timing t49. The disconnection detection is performed based on the voltage detected at this timing t49.

As described above, by discharging the battery cell C that needs to be discharged longer than the battery cell C that does not need to be discharged, it is possible to perform the discharge for equalization even when the abnormality is determined.

Returning to the above description of FIG. 2, in step S18, it is determined whether the number of equalization processes exceeds a predetermined number of times. If the number of equalization processes does not exceed the predetermined number of times, the process returns to step S13, and the abnormality determination and equalization processing are performed according to a predetermined schedule.

On the other hand, when the number of equalization processes exceeds a predetermined number, in step S19, the settings of the battery cell C and the like that require discharge set in step S12 are reset, and the process ends.

In this flowchart and the flow charts of equalization processing and discharge abnormality determination processing, the function of step S12 corresponds to the "discharge determination unit", and the functions of steps S32, S36, S42 to S44, and S47 to S49 are "switch control units". , And the functions of steps S16 and S40 correspond to the “abnormality detection unit”.

According to the embodiment described above, the following effects are obtained.

The internal resistance R of the connection member L between each battery cell C and the filter circuit 31 changes due to deterioration over time, and when a current for discharging is passed through the discharge circuit 34, the internal resistance R of the connection member L changes. The voltage of the capacitor 33 fluctuates due to the voltage drop of. Therefore, the voltage detected by the voltage detection circuit 21 after the noise is removed by the filter circuit 31 is different from the voltage of the battery cell C, which causes an error in the voltage of the battery cell C. Further, since the internal resistance R changes due to deterioration over time or the like, it is difficult to calculate the measurement error in advance based on the difference between the voltage of the capacitor 33 and the voltage of the battery cell C after equalization.

In the present embodiment, the discharge switch 22 is opened and closed between the detection timing t11 and the detection timing t20 in the voltage detection circuit 21 for the battery cell C determined to require discharge. By closing the discharge switch 22, even if the capacitor 33 is discharged due to the voltage drop in the connecting member L, the discharge switch 22 is opened and the capacitor 33 tries to return to the voltage of the battery cell C. do. By repeating these behaviors between the detection timing t11 and the detection timing t20, the capacitor 33 and the battery cell C are compared with the case where the discharge switch 22 is kept closed between the detection timing t11 and the detection timing t20. The voltage error of can be reduced. Therefore, the discharge of the capacitor 33 due to the voltage drop in the connection member L can be suppressed, the time for waiting for the voltage of the capacitor 33 to recover can be shortened, and the voltage of the battery cell C can be reduced without any special correction. The value of can be detected.

When the discharge switch 22 is opened and closed a plurality of times between the detection timing t11 and the detection timing t20 as in the present embodiment, the number of times the discharge switch 22 is opened increases, so that the discharge circuit 34 is used for equalization. The time for discharging is shortened. Therefore, in the present embodiment, in addition to the discharge time originally scheduled for equalization, the discharge for equalization is performed while the abnormality of the battery system is detected. Therefore, by securing the discharge time in addition to the discharge time for equalization, the necessary discharge for equalization can be performed.

In the abnormality detection, for example, a disconnection detection in the connecting member L or the like, a current is passed through a circuit including the discharge circuit 34, and the abnormality is detected based on the result. At the time of such abnormality detection, all the battery cells C including the battery cell C which does not need to be discharged for equalization are discharged. At this time, the discharge time of the battery cell C that needs to be discharged is made longer than the discharge time of the other battery cells C that are determined not to need to be discharged. While performing necessary detection in all battery cells C, the battery cell C that needs to be discharged discharges for a longer time than the battery cell C that does not need to discharge, so that discharge for equalization is possible.

Some abnormality detection detects an abnormality without using the result of discharging in the discharge circuit 34, such as measurement of the temperature of the battery cell C. Even when such an abnormality is detected, the battery cell C, which is determined to require discharging, is discharged for equalization. Therefore, it is possible to increase the time for discharging for equalization.

Between the detection timing t11 and the detection timing t20 in the voltage detection circuit 21, the discharge switch 22 is continuously opened and closed for each group of the battery cells C that need to be discharged. By continuously opening and closing the discharge switch 22 for each group, the discharge switch 22 is opened in one group and the capacitor 33 returns to the voltage of the battery cell C while the other groups are discharging. The time for this will be longer. Therefore, the voltage error between the capacitor 33 and the battery cell C can be further reduced, and the voltage value of the battery cell C can be quickly calculated with almost no error.

<Other embodiments>
The present invention is not limited to the above embodiment, and may be implemented as follows, for example.

-In the above embodiment, during the equalization process, the odd-numbered battery cell C group and the even-numbered battery cell C group and the group were continuously discharged, but as shown in FIG. 7, Between the detection timing t61 and the detection timing t68, the discharge switch 22 of the battery cell C determined to require discharge of one group may be opened and closed a plurality of times.

First, at the timing t61, the voltage of each battery cell C is detected by the voltage detection circuit 21. Then, when the detection by the voltage detection circuit 21 is completed, the discharge switch 22 of the odd-numbered battery cell C (for example, the battery cell C3) for discharging is turned on (closed state) at the timing t62, and the discharge is performed. Will be carried out. Meanwhile, the voltage of the corresponding capacitor 33 drops below the voltage of the battery cell C due to the voltage drop at the internal resistance R of the connecting member L.

After the discharge is performed for a predetermined time (for example, 3 milliseconds), the discharge switch 22 is turned off (open state) at the timing t63. Then, after the discharge switch 22 is turned off, after waiting for a time (for example, about 1 millisecond) for switching until the current does not flow reliably, the odd-numbered number that discharges again at the timing t64. The discharge switch 22 of the battery cell C (for example, the battery cell C3) is turned on (closed) and discharged. In this way, at timings t65 to timing t67, the discharge switch 22 of the odd-numbered battery cell C is opened and closed at a predetermined cycle.

Then, in the off state of the switch, after a predetermined time (for example, 1 millisecond) has elapsed, the next equalization process is performed. At the timing t68, the voltage is detected by the voltage detection circuit 21 for each battery cell C. This voltage is the post-discharge voltage after the discharge is performed at the timing t62 to the timing t67. Then, after the timing t68, the even-numbered battery cells C are discharged in the same manner as after the timing t62.

Between the detection timing t61 and the detection timing t68 in the voltage detection unit, the discharge switch 22 is opened and closed a plurality of times for the battery cell C of a certain group for the battery cell C that needs to be discharged. By discharging each group, it becomes easier to manage the discharged battery cell C.

-In the above embodiment, the voltage detection circuit 21 detects the voltage at a fixed cycle, but if the voltage is detected at a predetermined cycle scheduled in advance, the interval between the detection timing and the detection timing is not constant. good.

-In the above embodiment, the voltage detected by the voltage detection circuit 21 is not corrected, but the value of the battery cell C may be calculated from the detected voltage of the capacitor 33 by a well-known method. ..

In the above embodiment, the odd-numbered battery cell C group and the even-numbered battery cell C group are discharged twice between the detection timing t11 and the detection timing t20, but the number of times is different. You may. For example, the number of times of discharging may be different for each group, such as discharging the group of the odd-numbered battery cells C twice and discharging the group of the even-numbered battery cells C once. In this case, in the equalization process after the equalization process in which the group of the odd-numbered battery cells C is discharged a lot, the number of discharges is final, such as the group of the even-numbered battery cells C being discharged a lot. It should be the same as.

10 ... Storage battery, 20 ... Monitoring IC, 21 ... Voltage detection circuit, 22 ... Discharge switch, 31 ... Filter circuit, 32 ... Filter resistance, 33 ... Capacitor, 34 ... Discharge circuit, 35 ... Discharge resistance, C ... Battery cell, L … Connecting member.

Claims (6)

A storage battery (10) in which a plurality of battery cells (C) are connected in series, a filter circuit (31) provided for each battery cell and having a capacitor (33) connected to the battery cell, and the battery cell. A connection member (L) connecting between the filter circuit, a discharge switch (22) provided for each battery cell and connected in series to the battery cell via the connection member, and a discharge resistance (35). ), A battery control device (20) applied to a power supply system including the discharge circuit (34).
A voltage detection unit (21) provided for each battery cell and detecting the voltage of the battery cell from which noise has been removed by the filter circuit, and a voltage detection unit (21).
Based on the voltage of the battery cell detected by the voltage detection unit, a discharge determination unit that determines the necessity of discharge in the discharge circuit for each battery cell for equalization, and a discharge determination unit.
A switch control unit that opens and closes the discharge switch of the battery cell that is determined to require discharge by the discharge determination unit a plurality of times between the detection timing at which the voltage is detected by the voltage detection unit and the detection timing. Equipped with
When the switch control unit opens and closes the discharge switch a plurality of times, after closing and opening the discharge switch, the passage of time for recovering the voltage drop of the capacitor caused by the closing of the discharge switch. A battery control device that later closes the discharge switch again. An abnormality detection unit for detecting an abnormality in the power supply system is provided between the detection timing at which the voltage is detected by the voltage detection unit and the detection timing.
While the abnormality detection unit detects an abnormality, the switch control unit opens and closes the discharge switch of the battery cell that needs to be discharged by the discharge determination unit, and discharges in the discharge circuit. The battery control device according to claim 1. The abnormality detection unit detects the abnormality by causing the switch control unit to close the discharge switch and detecting the result of passing a current through the circuit including the discharge circuit.
When the abnormality is detected by the abnormality detection unit, the switch control unit sets the time for closing the discharge switch of the battery cell that needs to be discharged by the discharge determination unit. The battery control device according to claim 2, wherein the discharge switch of the other battery cell that does not require discharge is made longer than the time for closing the discharge switch. The abnormality detection unit detects the abnormality without causing the switch control unit to close the discharge switch.
The battery control according to claim 2, wherein when the abnormality detection unit detects the abnormality, the switch control unit opens and closes the discharge switch of the battery cell that needs to be discharged by the discharge determination unit. Device. The battery cells are divided into a plurality of groups so that the adjacent battery cells are in different groups from each other.
The switch control unit opens and closes the discharge switch of the battery cell for which the discharge determination unit determines that discharge is necessary between the detection timing at which the voltage is detected by the voltage detection unit and the detection timing. The battery control device according to any one of claims 1 to 4, which is continuously performed for each. The battery cells are divided into a plurality of groups so that the adjacent battery cells are in different groups from each other.
The switch control unit determines that the battery cell of a certain group needs to be discharged by the discharge determination unit between the detection timing at which the voltage is detected by the voltage detection unit and the detection timing. The battery control device according to any one of claims 1 to 4, wherein the discharge switch of the battery cell is opened and closed a plurality of times.

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