JP2020180891A - Disconnection detector of battery block - Google Patents

Abstract

To provide a disconnection detector of a battery block, which can determine the presence or absence of disconnection when current flows.SOLUTION: A battery ECU of a battery pack estimates reference temperature profiles as temperature of battery blocks when the battery blocks are charged and discharged without disconnection so as to estimate reference temperature. When an absolute value of difference between the estimated reference temperature and a temperature measured by a temperature sensor during the charge and discharge is a determination threshold or more, the disconnection is determined to exist in the battery blocks.SELECTED DRAWING: Figure 6

Description

The present invention relates to a disconnection detection device for a battery block having a disconnection determination unit for determining the presence or absence of disconnection of the secondary battery in a battery block having a plurality of secondary batteries connected in parallel.

Vehicles such as electric vehicles are equipped with a battery pack that stores the power supplied to the traction motor. In the battery pack, connecting a plurality of secondary batteries in series can increase the output voltage, and connecting a plurality of secondary batteries in parallel can increase the charge / discharge capacity. Therefore, by connecting a plurality of secondary batteries in parallel to form a battery block and further connecting a plurality of battery blocks in series to form a battery module, the output voltage can be adjusted while increasing the charge / discharge capacity.

In a battery pack including a battery module, a disconnection may occur in a part of a plurality of secondary batteries in the battery block, and the disconnection is detected. For example, in the disconnection inspection method disclosed in Patent Document 1, the controller first sets the internal resistance value of the battery block based on the assembled battery current value, which is the current value flowing through the battery module, and the voltage value of the battery block. To get. Next, the controller calculates the resistance ratio, which is the ratio of the internal resistance value of the reference battery block and the internal resistance value of the battery block to be inspected. Then, the controller detects the disconnection while specifying the number of disconnections of the battery block to be inspected based on the result of comparing the calculated resistance ratio with the predetermined reference resistance ratio.

Japanese Unexamined Patent Publication No. 2017-21162

In the disconnection inspection method of Patent Document 1, the disconnection is detected by utilizing the increase in the internal resistance value of the battery block that occurs when the disconnection occurs. However, since the internal resistance value of the battery block cannot be measured directly, it is calculated using the open circuit voltage, the closed circuit voltage, and the current. Since the open circuit voltage cannot be obtained when a current is flowing, the disconnection inspection method of Patent Document 1 cannot perform a disconnection inspection when a current is flowing.

An object of the present invention is to provide a disconnection detection device for a battery block capable of determining the presence or absence of disconnection when a current is flowing.

The disconnection detection device for the battery block for solving the above problems measures the temperature of the battery block having a plurality of secondary batteries charged and discharged by a charger or a load and connected in parallel, and the temperature of the battery block. The battery block includes a temperature sensor and a disconnection determination unit for determining the presence or absence of disconnection of the secondary battery in the battery block, and the disconnection determination unit is said to be charged / discharged when the charge / discharge is performed without the disconnection. When the absolute value of the difference between the estimated reference temperature, which is the temperature of the battery block, and the temperature measured by the temperature sensor during charging / discharging is equal to or greater than the determination threshold. The gist is to determine that the battery block has a disconnection.

According to this, the temperature of the battery block fluctuates due to the flow of the charging current or the discharging current. If the battery block is in a normal state, such a temperature change of the battery block can be estimated according to the charge / discharge of the secondary battery, and the reference temperature at a certain point can be estimated. If the battery block is broken, the temperature will change differently from that of the battery block in the normal state, so that the temperature measured by the temperature sensor will be different from the estimated reference temperature. Therefore, the presence or absence of disconnection of the battery block can be determined by comparing the difference between the reference temperature and the temperature measured by the temperature sensor with the determination threshold value. Therefore, it is possible to determine the presence or absence of disconnection in the battery block even when a current is flowing, such as during charging and discharging of the secondary battery.

Further, with respect to the disconnection detection device of the battery block, the disconnection determination unit determines the presence or absence of the disconnection during charging of the secondary battery, and the charging current flows at the reference temperature without the disconnection. The temperature may be determined based on the temperature change of the battery block at the time.

According to this, since the charge current of the secondary battery has a smaller fluctuation than the discharge current, it is easy to estimate the temperature change of the battery block. Therefore, the accuracy of the estimated reference temperature is higher during charging than during discharging. Therefore, the determination accuracy performed by comparing the estimated reference temperature with the temperature measured by the temperature sensor is improved.

Further, the disconnection detection device of the battery block is provided with a current sensor that measures the current flowing through the battery block when the battery block is charged and discharged, and the reference temperature is set by using the measured value of the current sensor. May be good.

According to this, the current value at the time of charging / discharging is acquired by the current sensor, and the reference temperature is estimated from the acquired current value. The amount of heat generated by the battery block changes according to the current flowing through the battery block. Therefore, even when the current is liable to fluctuate while the vehicle is running and it is difficult to predict the temperature change in advance, it is possible to determine whether or not the battery block is broken by using the measured value of the current sensor.

Further, with respect to the disconnection detection device of the battery block, the disconnection determination unit may perform correction to increase the reference temperature as the degree of deterioration of the secondary battery increases.
According to this, as the deterioration of the secondary battery progresses, the internal resistance increases and the temperature change of the battery block increases, so that the temperature of the battery block increases. Therefore, when estimating the reference temperature, the error between the reference temperature and the actual temperature of the battery block can be reduced and the accuracy of determining the presence or absence of disconnection can be improved by considering the deterioration of the secondary battery.

Further, regarding the disconnection detection device of the battery block, a battery module in which a plurality of the battery blocks are connected in series is provided, and the plurality of the battery blocks are arranged in a parallel direction in the battery module, and the plurality of temperature sensors are provided. A plurality of the battery blocks are arranged at intervals in the parallel direction of the battery blocks, and the disconnection determination unit sets the reference temperature according to the position of each temperature sensor in the battery module and the temperature measured by each temperature sensor. The presence or absence of the disconnection may be determined by comparison.

According to this, the temperature differs depending on the position of the battery block in the parallel arrangement direction. The central battery block in the parallel direction tends to have a higher temperature than the battery blocks at the ends in the parallel direction because it has low heat dissipation in addition to heat transfer from other battery blocks sandwiching the battery block. Therefore, the disconnection determination unit can determine that there is a disconnection when the temperature measured by the temperature sensor is different from the temperature characteristics according to the position in the parallel arrangement direction.

Further, regarding the disconnection detection device of the battery block, the disconnection determination unit estimates the internal resistance of the battery block in the state of disconnection from the internal resistance of the battery block, and the internal resistance of the battery block in the state of the disconnection. The difference between the disconnection temperature estimated from the above and the temperature measured by the temperature sensor is equal to or less than the comparison threshold, and the absolute difference between the estimated reference temperature and the temperature measured by the temperature sensor is absolute. When the value is equal to or higher than the determination threshold value, it may be determined that the battery block has a disconnection.

According to this, as the temperature fluctuation of the battery block, in addition to the temperature fluctuation due to the disconnection of the battery block, there is the temperature fluctuation due to the internal short circuit of the secondary battery, and the temperature fluctuation of the battery block is the temperature fluctuation due to the disconnection of the battery block. It is necessary to judge whether or not. The internal resistance of the battery block in the disconnected state can be estimated from the internal resistance of the battery block in the normal state. Further, the temperature at the time of disconnection of the battery block can be estimated from the internal resistance of the battery block in the disconnected state. Then, the disconnection determination unit compares the temperature at the time of disconnection with the temperature measured by the temperature sensor, and if the measured temperature is close to the temperature at the time of disconnection, determines that the temperature fluctuation of the battery block is the temperature fluctuation due to the disconnection. Therefore, the disconnection determination unit can determine whether or not the temperature fluctuation of the battery block is a temperature fluctuation due to an internal short circuit, and by performing the temperature fluctuation in combination with the determination threshold value, the determination accuracy of the presence or absence of the disconnection can be improved. ..

According to the present invention, it is possible to determine the presence or absence of disconnection when a current is flowing.

The schematic block diagram of the vehicle of an embodiment. Top view showing the battery module. The graph which shows the temperature profile at the time of a discharge, a quick charge and a normal charge. The graph which shows the reference temperature profile at the time of quick charge and the temperature profile at the time of disconnection. The graph which shows an example of the comparison between the measurement temperature and the reference temperature and the temperature at the time of disconnection. The figure which shows the control flow which determines the presence or absence of disconnection.

Hereinafter, an embodiment in which the battery block disconnection detection device is embodied will be described with reference to FIGS. 1 to 6.
As shown in FIG. 1, the vehicle 10 is equipped with a battery pack 11, a power control unit 20, a traveling motor 21 as a load, and a vehicle ECU 31. The battery pack 11 includes a battery module 12, a temperature sensor 13, a battery monitoring unit 16, a current sensor 17, and a battery ECU 18 as a disconnection determination unit. In the present embodiment, the battery module 12, the temperature sensor 13, the current sensor 17, and the battery ECU 18 constitute a disconnection detection device for the battery block Y, which will be described later.

In the vehicle 10, the traveling motor 21 is driven by the electric power supplied from the battery module 12 of the battery pack 11. The battery module 12 is connected to the traveling motor 21 via the power control unit 20.

The power control unit 20 is connected to the positive electrode terminal of the battery module 12 via the positive electrode side power line PL1, and the positive electrode side system main relay SMR1 is provided in the positive electrode side power line PL1. Further, the power control unit 20 is connected to the negative electrode terminal of the battery module 12 via the negative electrode side power line NL1, and the negative electrode side power line NL1 is provided with the negative electrode side system main relay SMR2.

When the positive electrode side system main relay SMR1 and the negative electrode side system main relay SMR2 are turned on by the vehicle ECU 31, the power control unit 20 converts the DC power supplied from the battery module 12 into AC power to the traveling motor 21. Output. Further, when the vehicle 10 decelerates or stops while the positive electrode side system main relay SMR1 and the negative electrode side system main relay SMR2 are turned on by the vehicle ECU 31, the power control unit 20 generates a traveling motor 21. The generated AC power is converted into DC power, and the DC power is output to the battery module 12. The battery module 12 stores the regenerative power generated by the traveling motor 21.

The vehicle 10 is configured as a plug-in type hybrid vehicle or an EV vehicle capable of charging the battery module 12 with electric power from a charger 24 installed in a charging stand, a parking lot, or the like. A power receiving connector 10a is arranged on the vehicle body side of the vehicle 10. The positive electrode side charging power line PL2 and the negative electrode side charging power line NL2 are connected to the power receiving connector 10a. The positive electrode side charging power line PL2 is provided with a positive electrode side charging relay R1, and the positive electrode side charging power line PL2 is connected to the positive electrode side power line PL1 via the positive electrode side system main relay SMR1. Further, the negative electrode side charging power line NL2 is provided with a negative electrode side charging relay R2, and the negative electrode side charging power line NL2 is connected to the negative electrode side power line NL1 via the negative electrode side system main relay SMR2.

Then, the power receiving connector 10a is connected to the charger 24, and the positive electrode side charging relay R1 and the negative electrode side charging relay R2, the positive electrode side system main relay SMR1 and the negative electrode side system main relay SMR2 are turned on by the vehicle ECU 31, so that the battery The module 12 is charged by the charger 24. At this time, no electric power is output from the power control unit 20 to the traveling motor 21.

The positive electrode side system main relay SMR1 and the negative electrode side system main relay SMR2 are turned on by the vehicle ECU 31 when the ignition switch of the vehicle 10 (not shown) is turned on or when the vehicle 10 is connected to the charger 24. When the battery module 12 is in an abnormal state such as over-discharging or over-charging, the positive electrode side system main relay SMR1 and the negative electrode side system main relay SMR2 are turned off by the vehicle ECU 31, and the battery module 12 is turned off by the power control unit 20 or the charger. Block from 24.

As shown in FIG. 2, the battery module 12 includes a plurality of battery blocks Y composed of a plurality of secondary batteries 12a connected in parallel. Examples of the secondary battery 12a include a lithium ion battery and a nickel hydrogen battery. In the battery module 12, a set of battery blocks Y is composed of a pair of secondary batteries 12a adjacent to each other in the parallel direction of the secondary batteries 12a. The battery blocks Y are connected in parallel by a plate-shaped bus bar 12b. Further, each battery block Y is connected to an electrode terminal having a pole different from that of the other battery blocks Y by a bus bar 12b, and a plurality of battery blocks Y are connected in series.

The battery monitoring unit 16 of the battery pack 11 is an integrated circuit. As shown in FIG. 1, the battery monitoring unit 16 is charged / discharged from a unit control unit 16a that controls the battery monitoring unit 16 in a centralized manner, a voltage measuring unit 16b that measures the voltage across each battery block Y, and a current sensor 17. The current measuring unit 16c for acquiring the current, the temperature acquiring unit 16d for acquiring the temperature T of the battery block Y from the temperature sensor 13, and the like are provided. In the following description, the temperature measured by the temperature sensor 13 may be simply referred to as the measured temperature T. The battery monitoring unit 16 monitors the state of the secondary battery 12a by each unit. The battery monitoring unit 16 may be operated by being supplied with electric power from the battery module 12.

The temperature sensor 13 detects the temperature T of the secondary battery 12a constituting each battery block Y of the battery module 12. As shown in FIG. 2, in the present embodiment, one battery module 12 is provided with three temperature sensors 13. The battery pack 11 is attached to one of the first temperature sensor 13a installed in the battery block Y at the center of the battery module 12 in the parallel direction and the secondary battery 12a constituting the battery block Y at one end in the parallel direction of the battery module 12. It is provided with an installed second temperature sensor 13b. Further, the battery pack 11 includes a third temperature sensor 13c installed on one of the secondary batteries 12a constituting the battery block Y at the other end of the battery module 12 in the parallel arrangement direction. The battery monitoring unit 16 sets the temperature measured by the first temperature sensor 13a as the first measured temperature T1 of the battery block Y at the center of the battery module 12 in the parallel arrangement direction. Further, the temperature measured by the second temperature sensor 13b is defined as the second measured temperature T2 of the battery block Y at one end in the parallel arrangement direction of the battery module 12. Further, the temperature measured by the third temperature sensor 13c is defined as the third measured temperature T3 of the battery block Y at the other end in the parallel arrangement direction of the battery module 12.

As shown in FIG. 1, the battery ECU 18 is an electronic control unit including a CPU 18a and a storage unit 18b including a RAM, a ROM, and the like. The CPU 18a and the storage unit 18b are signal-connected. The storage unit 18b stores a program for determining the presence or absence of disconnection of the battery block Y and a program for estimating various temperature profiles described later.

The battery ECU 18 may include dedicated hardware that executes at least a part of the various processes, for example, an integrated circuit for a specific application: ASIC. The battery ECU 18 may be configured as one or more processors operating according to a computer program, one or more dedicated hardware circuits such as an ASIC, or a circuit including a combination thereof. The processor includes a CPU and memories such as RAM and ROM. The memory stores a program code or a command configured to cause the CPU to execute the process. Memory, or computer-readable medium, includes anything that can be accessed by a general purpose or dedicated computer.

The battery ECU 18 determines whether or not the battery block Y is disconnected by using the temperature or current value acquired by the battery monitoring unit 16. The battery monitoring unit 16 and the battery ECU 18 can communicate with each other by a serial interface such as SPI (Serial Peripheral Interface). As a result, the battery monitoring unit 16 and the battery ECU 18 can acquire each other's information.

Further, the battery ECU 18 calculates the charge rate: SOC (State Of Charge) of the battery module 12. SOC is estimated by the current integration method. The current integration method is a method of estimating the charge rate by integrating the charge / discharge currents of the battery module 12. When the charging / discharging of the battery module 12 is started, the battery ECU 18 acquires the value of the charging / discharging current from the battery monitoring unit 16 and integrates the product of the charging / discharging current of the battery module 12 and the predetermined cycle at predetermined cycles. By doing so, the amount of change in the charge capacity of the battery module 12 is calculated. The battery ECU 18 calculates the amount of change in the charge rate of the battery module 12 by dividing the amount of change in the charge capacity of the battery module 12 by the full charge capacity of the battery module 12. The battery ECU 18 calculates the SOC of the battery module 12 by adding or subtracting the calculated change amount of the charging rate to the charging rate before charging / discharging the battery module 12.

When the calculated SOC is equal to or less than a preset lower limit threshold value, the battery ECU 18 sends limited output power information limiting the output power Wout of the battery module 12 to the vehicle ECU 31. Further, when the calculated SOC is equal to or higher than the preset upper limit threshold value, the battery ECU 18 sends the limited regenerative power information that limits the regenerative power Win input to the battery module 12 to the vehicle ECU 31. The battery ECU 18 and the vehicle ECU 31 can communicate with each other by a communication protocol such as CAN (Controller Area Network) or LIN (Local Interconnect Network).

The vehicle ECU 31 is an electronic control unit including a CPU and a storage unit including a RAM and a ROM. The vehicle ECU 31 controls the power control unit 20 based on the limited output power information and the limited regenerative power information sent from the battery ECU 18. The vehicle ECU 31 controls the power control unit 20 so as to limit the output from the battery module 12 to the traveling motor 21 according to the limited output power information, and the battery from the traveling motor 21 according to the limited regenerated power information. The power control unit 20 is controlled so as to limit the input of regenerative power to the module 12. Although not described in detail, the power limitation by the power control unit 20 is performed by controlling the switching frequency of the switching elements constituting the power control unit 20 and reducing the duty ratio.

Next, the disconnection detection device of the battery block Y will be described. In the present embodiment, the disconnection detection device for the battery block Y includes a battery module 12 having a plurality of battery blocks Y, first to third temperature sensors 13a to 13c, a battery ECU 18 as a disconnection determination unit, and a current sensor 17. It is composed of.

When charging / discharging is performed, if there is no disconnection in each battery block Y, each of the secondary batteries 12a in each battery block Y generates heat. The calorific value Q [J] of the secondary battery 12a is expressed by the following equation.

Q = R × I ² × t ... Equation R [Ω] is the internal resistance of the secondary battery 12a, and I [A] is the charging current or discharging current flowing through the secondary battery 12a during a predetermined time t [sec]. Represents the average value of. If one of the two secondary batteries 12a constituting the battery block Y has a disconnection in the secondary battery 12a provided with the temperature sensor 13, no current flows through the one secondary battery 12a due to charging / discharging. Therefore, the calorific value Q of the secondary battery 12a becomes zero. Therefore, the temperature T measured by the temperature sensor 13 is lower than that in the case where one of the secondary batteries 12a has no disconnection.

On the other hand, when the other secondary battery 12a, which is not provided with the temperature sensor 13, of the two secondary batteries 12a constituting the battery block Y has a disconnection, current flows only in one of the secondary batteries 12a. Then, since the current flows through one of the secondary batteries 12a almost twice, the calorific value Q of the one secondary battery 12a becomes about four times as large. Therefore, the temperature T measured by the temperature sensor 13 rises as compared with the case where the other secondary battery 12a has no disconnection.

Therefore, the temperature change of the battery block Y with the disconnection is different from the reference temperature which is the temperature of the battery block Y in the normal state. Therefore, if the difference between the temperature T measured by the temperature sensor 13 and the reference temperature Tb is widened and the absolute value of the temperature difference ΔT becomes equal to or higher than the preset determination threshold value, the battery block Y is said to have a disconnection. Can be judged.

The temperature change of the battery block Y varies depending on the magnitude of the current value flowing through the secondary battery 12a and also varies depending on the temperature of the secondary battery 12a and the deteriorated state. Therefore, in the present embodiment, when the disconnection determination is performed, the reference temperature Tb to be compared with the temperature T measured by the temperature sensor 13 at a certain point in time is changed depending on the situation at the time of temperature measurement of the battery block Y. The reference temperature Tb of the battery block Y at a certain point in time without disconnection can be estimated from the charge / discharge state of the battery block Y, and in the present embodiment, the reference temperature Tb correlates with the time and the temperature of the battery block Y. It is estimated from the reference temperature profile Pb having a relationship.

The storage unit 18b of the battery ECU 18 stores a program for estimating the reference temperature profile Pb according to the state of the secondary battery 12a. The reference temperature profile Pb is estimated based on the temperature profile P obtained in advance by experiments, simulations, or the like. The temperature profile P is stored in the storage unit 18b.

As shown in FIG. 3, as the temperature profile P, there are a temperature profile P1 at the time of normal charging and a temperature profile P2 at the time of quick charging. Note that quick charging is a charging method in which the charging time is shorter than that of normal charging. Therefore, in quick charging, the current value at the time of charging is larger than that in normal charging. Further, the temperature profile P3 at the time of discharging is also stored in the storage unit 18b of the battery ECU 18.

For example, the temperature profile P1 at the time of normal charging is stored as a temperature change with respect to a time when the battery temperature is 25 ° C., the environmental temperature is 25 ° C., and the normal charging is performed for 10 hours without deterioration of the battery. The other temperature profiles P are also stored as temperature changes with respect to time when charging or discharging is performed in a predetermined battery temperature, a predetermined environmental temperature, or a predetermined deterioration state.

Next, the temperature profile P when the charging current flows will be described as an example. Since the current value of the quick charge is larger than that of the normal charge, the temperature of the battery block Y in the temperature profile P2 of the quick charge is higher than that of the temperature profile P1 of the normal charge.

Therefore, the temperature profile P2 during quick charging has a higher temperature than the temperature profile P1 during normal charging at any time point. Then, both the temperature profiles P during rapid charging and normal charging show a temperature change in which the temperature rises rapidly at the start of charging and then gradually rises.

As shown by the broken line in FIG. 4, the battery ECU 18 selects the temperature profile P most suitable for the charge / discharge state of the secondary battery 12a, and estimates the reference temperature profile Pb by correcting the selected temperature profile P. .. For example, when the secondary battery 12a is normally charged, the temperature profile P1 at the time of normal charging is selected, and when the secondary battery 12a is rapidly charged, as shown by the solid line in FIG. The temperature profile P2 at the time of quick charging is selected. The correction of the selected temperature profile P is performed according to the temperature T of the battery block Y, the degree of deterioration of the secondary battery 12a, and the position of the battery block Y in the battery module 12 in the parallel direction. Therefore, the reference temperature profile Pb is estimated for each battery block Y.

Here, the temperature profile P corrected based on the battery block Y in the center in the parallel direction is represented as the first reference temperature profile Pb1, and the temperature profile P corrected based on the battery block Y at one end in the parallel direction is the second. It is expressed as a reference temperature profile Pb2. Further, the temperature profile P corrected based on the battery block Y at the other end in the parallel arrangement direction is referred to as a third reference temperature profile Pb3.

The temperature profile P indicates the temperature change of the battery charged or discharged from a predetermined temperature. When estimating the reference temperature profile Pb, the battery ECU 18 is selected so as to match the temperature T of the battery block Y at the start of charging / discharging with the temperature at the start of charging / discharging of the selected temperature profile P. Offset the entire profile P. Specifically, the temperature profiles so as to match the first to third measurement temperatures T1 to T3 of each battery block Y at the start of charging / discharging and the temperature at the start of charging / discharging of the selected temperature profile P, respectively. The first to third reference temperature profiles Pb1 to Pb3 are estimated by offsetting P.

Further, as the temperature of the secondary battery 12a decreases, the internal resistance R of the secondary battery 12a increases and the calorific value Q increases. On the other hand, as the temperature of the secondary battery 12a rises, the internal resistance R of the secondary battery 12a decreases and the calorific value Q decreases. Therefore, the battery ECU 18 corrects the selected temperature profile P so that the temperature rise of the selected temperature profile P becomes rapid when the entire selected temperature profile P is offset to the low temperature side. To do. Similarly, the battery ECU 18 corrects the selected temperature profile P so that the temperature rise of the selected temperature profile P becomes gradual when the entire selected temperature profile P is offset to the high temperature side. To do.

Specifically, the temperature at which the correction coefficient according to the ratio of the temperature at the start of charging / discharging of the selected temperature profile P and the temperature of the secondary battery 12a at the start of charging / discharging of the secondary battery 12a is selected is selected. It is corrected by multiplying the entire profile P. Further, how the temperature changes with respect to the calculated ratio is measured in advance by an experiment or the like, and the correction coefficient corresponding to the calculated ratio is stored in the storage unit 18b of the battery ECU 18.

The secondary battery 12a deteriorates as the charge / discharge time becomes longer, and the internal resistance R increases as the deterioration progresses. As the deterioration of the secondary battery 12a progresses and the internal resistance R increases, the calorific value Q also increases. As a result, the temperature of the battery block Y also rises. Therefore, when estimating the reference temperature profile Pb, the battery ECU 18 corrects the selected temperature profile P according to the degree of deterioration of the secondary battery 12a.

The degree of deterioration of the secondary battery 12a is estimated from the internal resistance R of the secondary battery 12a. The internal resistance R of the secondary battery 12a can be calculated by a well-known method. For example, the internal resistance R of the secondary battery 12a can be estimated by the IV plot. The IV plot is obtained by acquiring the current value and the voltage value when the charging current or the discharging current flows through the secondary battery 12a over a predetermined period or longer. The internal resistance R of the secondary battery 12a is the value of the coefficient (inclination) of the regression line when the equation which is the regression line of the current value and the voltage value is calculated by the least squares method.

The battery ECU 18 estimates the degree of deterioration of the battery block Y from the difference between the estimated internal resistance R and the internal resistance R of the secondary battery 12a that has not deteriorated. The battery ECU 18 corrects the selected temperature profile P according to the ratio of the estimated internal resistance R to the internal resistance R of the secondary battery 12a without deterioration. The internal resistance R of the secondary battery 12a without deterioration is stored in advance in the storage unit 18b. Further, how the temperature changes with respect to the calculated ratio is measured in advance by an experiment or the like, and the correction coefficient corresponding to the calculated ratio is stored in the storage unit 18b of the battery ECU 18. Then, when estimating the reference temperature profile Pb, the temperature profile P selected according to the deterioration is corrected by using the correction coefficient stored in the storage unit 18b. The temperature of the corrected temperature profile P increases as the degree of deterioration increases.

Further, the temperature of the battery block Y differs depending on the position of the battery module 12 in the parallel arrangement direction. The battery block Y in the center of the parallel direction has low heat dissipation in addition to heat transfer from other battery blocks Y sandwiching the battery block Y in the center of the parallel direction, so that the battery block Y at the end in the parallel direction has lower heat dissipation. The temperature rises. Therefore, the temperature change differs depending on the position of the battery block Y in the parallel arrangement direction. Therefore, when estimating the reference temperature profile Pb, the battery ECU 18 corrects the selected temperature profile P by a correction coefficient different for each battery block Y. Further, how the temperature changes according to the position of the battery block Y in the parallel direction is measured in advance by an experiment or the like, and the correction coefficient according to the position of the battery block Y in the parallel direction is calculated by the battery ECU 18. It is stored in the storage unit 18b of. The first reference temperature profile Pb1 is estimated to be higher in temperature than the second reference temperature profile Pb2 and the third reference temperature profile Pb3.

Therefore, in the present embodiment, when determining the presence or absence of disconnection, the battery ECU 18 determines the charge / discharge state of the secondary battery 12a from the charging method or the like, and selects a suitable temperature profile P. Further, the battery ECU 18 estimates the first to third reference temperature profiles Pb1 to Pb3 according to the temperature, the degree of deterioration, and the position in the parallel arrangement direction of the battery module 12 from the selected temperature profile P.

As shown in FIG. 5, the battery ECU 18 measures the time from the start of charging / discharging at the time of charging / discharging. When determining the presence or absence of disconnection, in the first to third reference temperature profiles Pb1 to Pb3, the temperature corresponding to the time Tc from the start of charging / discharging at the time of determination is set to the first to third reference temperatures Tb1 to Tb3. Estimate as. Note that FIG. 5 illustrates a case where the third reference temperature Tb3 is estimated using the third reference temperature profile Pb3.

Then, the battery ECU 18 calculates the temperature difference ΔT between the first to third measurement temperatures T1 to T3 and the first to third reference temperatures Tb1 to Tb3 of each battery block Y, and the calculated temperature difference ΔT is set in advance. When the temperature difference ΔT exceeds the judgment threshold value, it is determined that the battery block Y having the temperature difference ΔT equal to or higher than the judgment threshold value has a disconnection. Therefore, the battery ECU 18 can identify the battery block Y having a disconnection. When the battery ECU 18 determines that the battery block Y has a disconnection, the battery ECU 18 uses the limited output power information that limits the output power Wout of the battery module 12 and the limited regenerative power information that limits the regenerative power Win input to the battery module 12 to the vehicle. It may be transmitted to the ECU 31.

For the determination threshold value, the temperature of the battery block Y having a disconnection and the temperature of the battery block Y having no disconnection are measured by an experiment, and the temperature difference ΔT is calculated. The temperature difference ΔT is set in consideration of a margin such as an individual difference of the temperature sensor 13 and a measurement error, and is set slightly lower than the temperature difference calculated at the time of actual measurement.

Further, the temperature fluctuation of the battery block Y fluctuates not only when the battery block Y has a disconnection as described above, but also when an internal short circuit occurs in the secondary battery 12a. Specifically, when an internal short circuit occurs in the secondary battery 12a, the temperature of the battery block Y rises. Therefore, it may not be possible to determine whether the temperature rise due to the disconnection of the battery block Y or the temperature rise due to the internal short circuit of the secondary battery 12a based on the temperature of the battery block Y alone.

In order to determine whether or not the temperature fluctuation of the battery block Y is the temperature fluctuation due to the disconnection, the battery ECU 18 estimates the temperature Tt at the time of disconnection as the temperature corresponding to the case where the battery block Y is disconnected. The disconnection temperature Tt is estimated based on the disconnection assumption profile P'obtained in advance by experiments, simulations, and the like. The disconnection assumption profile P'is stored in the storage unit 18b corresponding to the temperature profile P. The disconnection assumption profile P'includes a disconnection assumption profile P'1 during normal charging, a disconnection assumption profile P'2 during quick charging, and a disconnection assumption profile P'3 during discharge. For example, the disconnection assumption profile P'1 during normal charging has a battery temperature of 25 ° C., an environmental temperature of 25 ° C., a state in which the battery is not deteriorated, and the other secondary battery 12a in which the temperature sensor of the battery block Y is not provided. It is stored as a temperature change with respect to the time when normal charging is performed for 10 hours with a disconnection in the battery. Other assumed disconnection profiles P'are also stored as temperature changes with respect to time when charging or discharging is performed with a predetermined battery temperature, a predetermined environmental temperature, a predetermined deterioration state, and a disconnection in the secondary battery 12a. Has been done.

The disconnection assumption profiles P'1 to P'3 are lower in temperature than the temperature change when an internal short circuit occurs, and are higher in temperature than the temperature profiles P1 to P3.
When determining the presence or absence of disconnection, the battery ECU 18 selects a disconnection assumption profile P'corresponding to the selected temperature profile P that matches the charge / discharge state of the secondary battery 12a. Then, the selected disconnection assumption profile P'is corrected according to the temperature and deterioration state of the secondary battery 12a and the position of the battery block Y in the battery module 12 in the parallel arrangement direction in the same manner as the temperature profile P. Estimate the temperature profile Pt.

Here, the temperature profile Pt at the time of disconnection corrected by the correction coefficient of the battery block Y in the center of the parallel arrangement direction is referred to as the first temperature profile Pt1 at the time of disconnection, and the disconnection corrected by the correction coefficient of the battery block Y at one end in the parallel arrangement direction. It is assumed that the hourly temperature profile Pt is represented by the second disconnection time temperature profile Pt2. Further, the temperature profile Pt at the time of disconnection corrected by the correction coefficient of the battery block Y at the other end in the parallel arrangement direction is referred to as the third temperature profile Pt3 at the time of disconnection.

In the first to third disconnection temperature profiles Pt1 to Pt3, the battery ECU 18 estimates the temperature corresponding to the time Tc from the start of charging / discharging at the time of determination as the first to third disconnection temperatures Tt1 to Tt3. ..

The battery ECU 18 measures the temperature of the temperature sensor 13 higher than the first to third reference temperatures Tb1 to Tb3 when any of the measured temperatures T1 to T3 of the temperature sensor 13 is higher than the first to third reference temperatures Tb1 to Tb3. T1 to T3 are compared with each disconnection temperature Tt1 to Tt3. Then, it is determined that the battery block Y whose absolute value of the temperature difference ΔTt at the time of disconnection is equal to or less than the comparison threshold value is disconnected. That is, the battery ECU 18 determines that the battery block Y, which shows a temperature T close to the temperature Tt at the time of disconnection, has a disconnection.

The comparison threshold value is set in consideration of a margin such as an individual difference of the temperature sensor 13 and a measurement error that can be added to the disconnection assumption profile P'.
Therefore, the battery ECU 18 compares the measured temperatures T1 to T3 with the reference temperatures Tb1 to Tb3, and also compares the measured temperatures Tt1 to T3 with the disconnection temperatures Tt1 to Tt3 when the measured temperatures T1 to T3 are higher than the reference temperatures Tb1 to Tb3. When it is determined that the battery block Y has a disconnection in both determinations, it is determined that the battery block Y has a disconnection.

Next, the disconnection determination process by the battery ECU 18 will be described with reference to FIG. When the power receiving connector 10a is connected to the charger 24 and the battery module 12 is rapidly charged, it is determined whether or not the battery block Y is broken. Further, it is assumed that of the three battery blocks Y, the battery block Y at the other end of the battery module 12 in the parallel arrangement direction has a disconnection. Of the battery blocks Y at the other end of the battery module 12 in the parallel arrangement direction, the temperature when the other secondary battery 12a, which is not provided with the third temperature sensor 13c, has a disconnection is defined as the third measurement temperature T3. 3 The temperature when one of the secondary batteries 12a provided with the temperature sensor 13c has a disconnection is defined as the third measurement temperature T3'.

When the power receiving connector 10a is connected to the charger 24 and the quick charging method is selected, the vehicle ECU 31 sends information to the battery ECU 18 that the quick charging is performed. When charging is started, the battery ECU 18 measures the time from the start of charging. Further, the storage unit 18b stores the first to third measurement temperatures T1 to T3 of each battery block Y at the start of charging.

In step S1, the battery ECU 18 selects the temperature profile P that best suits the charge / discharge state. Here, since the battery ECU 18 receives the information indicating that the battery ECU 18 is rapidly charging, the temperature profile P2 at the time of rapid charging is selected.

Next, in step S2, the battery ECU 18 corrects the selected temperature profile P2 at the time of quick charging, estimates the first to third reference temperature profiles Pb1 to Pb3 for each battery block Y, and stores the storage unit 18b. Temporarily memorize.

Next, in step S3, the battery ECU 18 estimates the temperature corresponding to the timed time Tc in the estimated first to third reference temperature profiles Pb1 to Pb3 as the first to third reference temperatures Tb1 to Tb3.

Next, in step S4, the battery ECU 18 acquires and acquires the temperature difference ΔT between the first to third measurement temperatures T1 to T3 of each battery block Y and the corresponding first to third reference temperatures Tb1 to Tb3. It is determined whether or not the absolute value of the temperature difference ΔT is equal to or greater than the determination threshold. Then, if there is a battery block Y in which the temperature difference ΔT is equal to or greater than the determination threshold value, that is, if YES in step S4, the battery ECU 18 proceeds to step S5. Specifically, as shown in FIG. 5, it is determined that the temperature difference ΔT between the third measurement temperature T3, T3'and the corresponding third reference temperature Tb3 is equal to or greater than the determination threshold value.

In step S5, the battery ECU 18 determines whether or not the measured temperature T of the battery block Y whose temperature difference ΔT is equal to or greater than the determination threshold value is higher than the corresponding reference temperature Tb. Then, when the measurement temperature T is higher than the corresponding reference temperature Tb, that is, when YES in step S5, the battery ECU 18 proceeds to step S6. Specifically, as shown in FIG. 5, when there is a disconnection in the other secondary battery 12a of the battery block Y at the other end in the parallel arrangement direction of the battery module 12 in which the third temperature sensor 13c is not provided. The third measurement temperature T3 is determined to be higher than the corresponding reference temperature Tb3.

On the other hand, when the measurement temperature T is equal to or lower than the corresponding reference temperature Tb, that is, when NO in step S5, the battery ECU 18 determines that the battery block Y has a disconnection (step S7). Specifically, as shown in FIG. 5, the third measurement temperature T3'of the battery block Y at the other end in the parallel direction has a temperature difference ΔT from the third reference temperature Tb3 equal to or greater than the determination threshold value and the reference temperature. Since it is Tb or less, the battery ECU 18 determines that the battery block Y at the other end in the parallel arrangement direction has a disconnection. In this case, of the battery blocks Y at the other end in the parallel arrangement direction, one of the secondary batteries 12a provided with the third temperature sensor 13c has a disconnection, and the amount of heat generated by the one secondary battery 12a becomes small. , The third measurement temperature T3'is lower than the case where there is no disconnection.

In step S6, the battery ECU 18 estimates the first to third disconnection temperature profiles Pt1 to Pt3, and estimates the first to third disconnection temperatures Tt1 to Tt3. Then, the temperature difference ΔTt at the time of disconnection between the measured temperature T higher than the reference temperature Tb and the corresponding first to third disconnection temperatures Tt1 to Tt3 is acquired, and the acquired temperature difference ΔTt at the time of disconnection is equal to or less than the comparison threshold value. Judge whether or not. Then, if there is a battery block Y in which the temperature difference ΔTt at the time of disconnection is equal to or less than the comparison threshold value, that is, if YES in step S6, the battery ECU 18 determines that the battery block Y has a disconnection (step S7). Specifically, as shown in FIG. 5, the third measurement temperature T3 of the battery block Y at the other end in the parallel direction has a temperature difference ΔT from the third reference temperature Tb3 equal to or greater than the determination threshold value and the third disconnection. Since the temperature difference ΔTt at the time of disconnection from the hourly temperature Tt3 is equal to or less than the comparison threshold value, the battery ECU 18 determines that the battery block Y at the other end in the parallel arrangement direction has a disconnection. In this case, of the battery blocks Y at the other end in the parallel arrangement direction, the other secondary battery 12a not provided with the third temperature sensor 13c has a disconnection, and the other secondary battery 12a provided with the third temperature sensor 13c is provided. Since the amount of heat generated by the battery 12a is large, the third measurement temperature T3 is higher than when there is no disconnection.

On the other hand, if there is a battery block Y in which the temperature difference ΔTt at the time of disconnection is larger than the comparison threshold value, that is, if NO in step S6, the battery ECU 18 determines that there is no disconnection in the battery block Y (step S8). At this time, it may be determined that the secondary battery 12a of the battery block Y has an internal short circuit. When determining that an internal short circuit has occurred, the battery ECU 18 sends information to the vehicle ECU 31 that an internal short circuit has occurred. Then, the vehicle ECU 31 turns off the positive electrode side system main relay SMR1 and the negative electrode side system main relay SMR2.

If there is no battery block Y whose temperature difference ΔT is equal to or greater than the determination threshold value, that is, if NO in step S4, the battery ECU 18 determines that there is no disconnection (step S8).
After that, the battery ECU 18 ends the process.

As shown in FIG. 5, when the battery block Y at the other end in the parallel arrangement direction has a disconnection, the third measurement temperature T3, T3'is abnormally larger or smaller than the third reference temperature Tb3. If the three battery blocks Y are normal, the first to third measurement temperatures T1 to T3 are arranged side by side so as to follow the first to third reference temperature profiles Pb1 to Pb3 as shown by the broken line in FIG. The first measurement temperature T1 in the center of the direction has the highest temperature. However, if the battery block Y at the other end in the parallel arrangement direction has a disconnection, the arrangement of the first to third measurement temperatures T1 to T3 will be different from the normal state, so that the battery ECU 18 will perform the first to third measurements. Based on the temperatures T1 to T3, it is possible to determine whether or not the battery block Y is broken.

According to the above embodiment, the following effects can be obtained.
(1) The battery ECU 18 estimates the reference temperature profile Pb of the battery block Y when the charging current is flowing through the battery block Y, and estimates the reference temperature Tb. The temperature T of the battery block Y with a disconnection becomes a temperature different from the reference temperature Tb of the normal battery block Y, and the difference is widened. Therefore, the presence or absence of disconnection of the battery block Y can be determined by comparing the difference between the estimated reference temperature Tb and the measured temperature T with the determination threshold value. Therefore, it is possible to determine whether or not there is a disconnection in the battery block Y even when a charging current is flowing through the secondary battery 12a.

(2) The battery ECU 18 determines whether or not there is a disconnection during charging of the secondary battery 12a. Since the charging current of the secondary battery 12a has a smaller fluctuation than the discharging current, it is easy to estimate the reference temperature profile Pb at the time of charging. Therefore, the accuracy of the estimated reference temperature profile Pb at the time of charging is higher than that of the reference temperature profile Pb at the time of discharging, and the accuracy of determining the presence or absence of disconnection is high.

(3) The battery ECU 18 corrects the reference temperature profile Pb to increase as the degree of deterioration of the secondary battery 12a increases. As the deterioration of the secondary battery 12a progresses, the internal resistance R of the secondary battery 12a increases and the amount of heat generated by the secondary battery 12a increases, so that the temperature of the battery block Y increases. Therefore, when estimating the reference temperature profile Pb, by considering the deterioration of the secondary battery 12a, the error between the reference temperature profile Pb and the actual temperature change is reduced, and the accuracy of determining the presence or absence of disconnection is improved. Can be done.

(4) The battery module 12 is configured by arranging a plurality of battery blocks Y in parallel, and a temperature sensor 13 is arranged in each battery block Y. The first to third temperature sensors 13a to 13c are arranged at intervals in the parallel direction. Then, the battery ECU 18 compares the first to third reference temperatures Tb1 to Tb3 corresponding to the positions of the temperature sensors 13a to 13c with the measured temperatures T1 to T3 to determine the presence or absence of disconnection. The temperatures of the first to third reference temperatures Tb1 to Tb3 differ depending on the positions of the battery blocks Y in the parallel arrangement direction. Therefore, the battery ECU 18 can determine that there is a disconnection when the measured temperatures T1 to T3 differ from the temperature characteristics according to the positions of the first to third reference temperatures Tb1 to Tb3 in the parallel direction.

(5) The battery ECU 18 estimates the temperature profile Pt at the time of disconnection as the temperature change of the battery block Y in the state of disconnection, and estimates the temperature Tt at the time of disconnection. Then, when the difference between the measured temperature T and the temperature Tt at the time of disconnection is equal to or less than the comparison threshold value and the difference between the measured temperature T and the measured temperature T is equal to or greater than the determination threshold value, it is determined that the battery block Y has a disconnection. To do. Therefore, the battery ECU 18 can determine whether or not the temperature fluctuation of the battery block Y is a temperature fluctuation due to an internal short circuit, and by performing the temperature fluctuation in combination with the determination threshold value, it is possible to improve the determination accuracy of the presence or absence of disconnection. ..

(6) The battery ECU 18 corrects the reference temperature profile Pb to be higher as the temperature of the secondary battery 12a is lower. When the temperature of the secondary battery 12a is low, the internal resistance R of the secondary battery 12a increases and the amount of heat generated by the secondary battery 12a increases, so that the temperature of the battery block Y increases. Therefore, when estimating the reference temperature profile Pb, by adding the temperature of the secondary battery 12a, the error between the reference temperature profile Pb and the actual temperature change is reduced and the accuracy of determining the presence or absence of disconnection is improved. Can be done.

In addition, this embodiment can be implemented by changing as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
○ At the time of discharging the battery module 12, the presence or absence of disconnection may be determined by estimating the reference temperature profile Pb at the time of discharging.

○ The determination using the disconnection temperature Tt may be performed before the determination using the reference temperature Tb.
○ The presence or absence of disconnection of the battery block Y may be determined only by the determination using the reference temperature Tb without performing the determination using the disconnection temperature Tt.

○ The reference temperature Tb may be estimated using the measured value of the current sensor 17. In this case, the current during charging / discharging is measured by the current sensor 17 and acquired by the battery monitoring unit 16. The battery ECU 18 acquires the measured value of the current sensor 17 from the battery monitoring unit 16 and calculates the time average of the acquired current value. The calorific value Q of the battery block Y is estimated based on the current value flowing through the battery block Y, and the temperature of the battery block Y is estimated from the calorific value Q. Since the calorific value Q of the battery block Y changes according to the current flowing through the battery block Y, the current tends to fluctuate while the vehicle is running, and even when it is difficult to predict the temperature change in advance, the current sensor 17 The reference temperature Tb can be estimated using the measured value of, and the presence or absence of disconnection of the battery block Y can be determined from the comparison between the reference temperature Tb and the measured temperature T.

○ The number of battery blocks Y constituting the battery module 12 may be four or more.
○ The temperature sensor 13 may not be provided in each battery block Y. Even when the battery block Y not provided with the temperature sensor 13 is disconnected, the temperature change of the temperature sensor 13 close to the disconnected battery block Y is different from the case where there is no disconnection. Therefore, even in this case, it can be determined that any of the battery blocks Y of the battery module 12 has a disconnection.

○ When estimating the reference temperature profile Pb, it is not necessary to make corrections based on the degree of deterioration of the secondary battery 12a of the temperature profile P. Further, it is not necessary to correct the temperature profile P by the temperature of the secondary battery 12a.

○ The number of secondary batteries 12a connected in parallel in the battery block Y may be three or more. In this case, as the number of secondary batteries 12a increases, the calorific value Q of the battery block Y decreases, so that the temperature of the reference temperature profile Pb is also set to decrease.

○ The number of battery blocks Y constituting the battery module 12 may be one.
○ The reference temperature profile Pb may be stored in advance in the storage unit of the battery ECU 18.

○ As a method of determining whether the temperature fluctuation of the battery block Y is due to the disconnection of the battery block Y or the internal short circuit of the secondary battery 12a, other than comparing the measured temperature T with the temperature Tt at the time of disconnection, the battery block The voltage across Y may be compared. When an internal short circuit occurs, the voltage across the battery block Y drops, but when the wire is broken, the voltage across the battery block Y does not drop. Therefore, the voltage across the battery block Y is compared with the voltage across the battery block Y in a state where there is no disconnection, and when the voltage difference is equal to or less than the threshold value, it is determined that the battery block Y has a disconnection.

T ... temperature (measured temperature), Tb ... reference temperature, Tt ... disconnection temperature, Y ... battery block, 12 ... battery module, 12a ... secondary battery, 13 ... temperature sensor, 17 ... current sensor, 18 ... disconnection determination unit Battery ECU as, 21 ... Traveling motor as load, 24 ... Charger.

Claims (6)

A battery block having multiple secondary batteries charged and discharged by a charger or load and connected in parallel.
A temperature sensor that measures the temperature of the battery block and
It has a disconnection determination unit for determining the presence or absence of disconnection of the secondary battery in the battery block.
The disconnection determination unit estimates a reference temperature which is the temperature of the battery block when the charging / discharging is performed without the disconnection.
When the absolute value of the difference between the estimated reference temperature and the temperature measured by the temperature sensor during charging / discharging is equal to or greater than the determination threshold value, it is determined that the battery block has a disconnection. A device for detecting disconnection of a battery block. The disconnection determination unit determines the presence or absence of the disconnection during charging of the secondary battery, and the reference temperature is based on the temperature change of the battery block when the charging current is flowing without the disconnection. The battery block disconnection detection device according to claim 1, which is the temperature determined by the above. The disconnection of the battery block according to claim 1, further comprising a current sensor that measures the current flowing through the battery block when the battery block is being charged and discharged, and the reference temperature is set by using the measured value of the current sensor. Detection device. The disconnection detecting device for a battery block according to any one of claims 1 to 3, wherein the disconnection determining unit makes a correction to increase the reference temperature as the degree of deterioration of the secondary battery increases. A battery module in which a plurality of the battery blocks are connected in series is provided, the plurality of the battery blocks are arranged in a parallel direction in the battery module, and the temperature sensors are spaced apart in the parallel direction of the plurality of battery blocks. The disconnection determination unit determines the presence or absence of the disconnection by comparing the reference temperature according to the position of each temperature sensor in the battery module with the temperature measured by each temperature sensor. The battery block disconnection detection device according to any one of claims 1 to 4. The disconnection determination unit estimates the internal resistance of the battery block in the state of disconnection from the internal resistance of the battery block, the temperature at the time of disconnection estimated from the internal resistance of the battery block in the state of disconnection, and the above. When the difference from the temperature measured by the temperature sensor is equal to or less than the comparison threshold, and the absolute value of the difference between the estimated reference temperature and the temperature measured by the temperature sensor is equal to or greater than the determination threshold. The battery block disconnection detection device according to any one of claims 1 to 5, wherein it is determined that the battery block has a disconnection.