Battery system

Abstract

To provide a battery system capable of suppressing unnecessary input / output restrictions.SOLUTION: A cell system includes charging state determination means for determining whether a present charging state is a rapid charging state, estimation means for estimating the temperature difference between the inside and outside of a battery pack, and control means for restricting the input / output of the battery pack depending on an estimation result of the estimation means. The estimation means switches information to be used for estimation depending on whether a determination result by the charging state determination means is a rapid charging state or not.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a battery system.

Background Art

[0002] Patent Document 1 discloses a technique for restricting the input / output of a battery pack based on the estimated result of the maximum temperature inside the battery pack.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique disclosed in Patent Document 1, since the tendency of the temperature difference between the inside and outside is different between the normal charging state and the rapid charging state, there is a possibility that input / output restriction is performed even when it is not necessary.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a battery system capable of suppressing unnecessary input / output restriction.

Means for Solving the Problems

[0006] In order to solve the above-described problems and achieve the object, a battery system according to the present invention includes a charging state determination means for determining whether or not the current charging state is a rapid charging state, an estimation means for estimating the temperature difference between the inside and outside of the battery pack, and a control means for performing input / output restriction of the battery pack according to an estimation result of the estimation means. The estimation means is characterized in that information used for estimation is switched according to whether or not the determination result by the charging state determination means is a rapid charging state.

[0007] This allows for the estimation of the internal and external temperature difference in accordance with the rapid charging process, which reduces the internal and external temperature difference during rapid charging, thereby suppressing unnecessary input / output restrictions.

[0008] Furthermore, in the above, the information used by the estimation means for estimation is a map showing the relationship between ambient temperature and the temperature difference between the inside and outside, and the map includes an internal-to-external temperature difference map for rapid charging used during rapid charging of the battery pack, and a normal internal-to-external temperature difference map used when the battery pack is not being rapidly charged.

[0009] This allows for the estimation of the internal and external temperature difference during rapid charging, when the internal and external temperature difference is small, by using an internal and external temperature difference map for rapid charging, thereby suppressing unnecessary input / output restrictions. [Effects of the Invention]

[0010] The battery system according to the present invention has the effect of suppressing unnecessary input / output restrictions because it can estimate the internal and external temperature difference in accordance with the rapid charging process when the internal and external temperature difference is small. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows the configuration of a battery system according to an embodiment. [Figure 2] Figure 2 is a flowchart showing the procedure for limiting the input and output of a battery pack based on the estimation of the maximum internal temperature of the battery pack in a battery system according to the embodiment. [Figure 3] Figure 3 is a map showing the relationship between ambient temperature and the temperature difference between the inside and outside of the battery system according to the embodiment. [Modes for carrying out the invention]

[0012] The following describes embodiments of the battery system according to the present invention. However, the present invention is not limited to these embodiments.

[0013] In the following, we will describe a lithium-ion battery pack, that is, a battery pack made up of multiple lithium-ion unit batteries, but other types of battery packs may also be used. For example, a nickel-metal hydride battery pack may be used. Furthermore, we will describe the battery pack as being constructed by connecting multiple unit batteries in series, but of course, a battery pack may also be constructed by connecting multiple unit batteries in parallel. Alternatively, multiple unit batteries may be constructed as a single battery pack using both series and parallel connections.

[0014] The number and placement of various sensors described below are illustrative examples for illustrative purposes only; other numbers of sensors may be used, and their placement can be arbitrarily determined. For example, while an intake air temperature sensor is described as a sensor for detecting ambient temperature, sensors that detect ambient air temperature or the temperature near the battery pack can also be used.

[0015] The power supply circuit configuration, including the battery pack, will be described as using a battery pack, system main relay, voltage converter, smoothing capacitor, and inverter. However, other elements may be added as needed. For example, a configuration including a DC / DC converter and low-voltage power supply may also be used.

[0016] Furthermore, although this explanation assumes the use of one motor-generator having both motor and generator functions as the rotating electric machine connected to the power supply circuit including the battery pack, it is also possible to use two motor-generators. In that case, it is also possible to use one rotating electric machine having only motor functions and one rotating electric machine having only generator functions.

[0017] Figure 1 shows a battery system 1, which is the part of a hybrid vehicle control system that controls the operation of a hybrid vehicle equipped with a battery pack and a rotating electric machine, that is related to the control of the input and output of the battery pack. This battery system 1 has a function to limit the input and output of the battery pack based on the surface temperature of the battery pack, but in particular, it has a function to estimate the maximum internal temperature of the battery pack and to limit the input and output based on that estimated maximum temperature.

[0018] This battery system 1 comprises a battery pack 2 composed of multiple battery cells 20, a system main relay 10, a battery pack-side smoothing capacitor 11, a voltage converter 12, an inverter-side smoothing capacitor 14, an inverter 16, a rotating electric machine 18, a current sensor 31, a temperature sensor 32, a voltage sensor 33, an intake air temperature sensor 34 as an ambient temperature sensor, an I / V / T detection unit 41 connected to these sensors to detect current I, voltage V, and temperature T respectively, a cooling airflow input unit 42 for inputting the cooling airflow value, and a control device 6 that controls the operation of these components as a whole. In this case, the control device 6 corresponds to a battery pack input / output control device.

[0019] The battery pack 2 is a rechargeable secondary battery configured to obtain a desired output voltage and output current by connecting multiple lithium-ion unit batteries in series as battery cells 20. The desired output voltage can be, for example, a terminal voltage of approximately 200V. In this case, the battery pack 2 can be configured by connecting 100 or more lithium-ion battery cells 20 in series.

[0020] The current sensor 31 provided in the battery pack 2 has a function of detecting the input / output current of the battery pack 2, and is arranged to be connected in series to at least one of both terminals of the battery pack 2. When there is one current sensor 31, the detected value of the current sensor 31 will detect the current value in the battery pack 2. When the current sensor 31 is provided at both terminals of the battery pack 2 respectively, in the I / V / T detection unit 41, the difference between the detected values of the two current sensors is obtained, and when it exceeds a predetermined allowable difference value, for example, it is detected that the current sensor 31 is abnormal.

[0021] In this way, the current sensor 31 is provided to obtain the current value input / output to the battery pack 2. The current value input / output to the battery pack 2 is due to the driving power, regenerative power, etc. of the rotating electrical machine 18 which is the load, and the magnitude of the value indicates the magnitude of the current load. In this way, the data of the current value obtained by the current sensor 31 is transmitted to the control device 6 via the I / V / T detection unit 41 as the data of the current load 51. When abnormalities between a plurality of current sensors 31 are monitored, it outputs to that effect, performs processing to obtain a correct current value, and data of one correct current value is transmitted to the control device 6.

[0022] The voltage sensor 33 provided in the battery pack 2 has a function of detecting the battery voltage of the battery cells 20 constituting the battery pack 2, and a plurality of them are used. In the example of FIG. 1, the state where five voltage sensors 33 are arranged at equal intervals along the arrangement direction of the battery cells 20 constituting one battery pack 2 is shown.

[0023] In this way, since the voltage sensor 33 has a function of detecting the respective battery voltages of the battery cells 20 at a plurality of arbitrarily determined arrangement positions in the battery pack 2, these can be called voltage detection units. The voltage sensor 33 is connected to the I / V / T detection unit 41, and via this, data of the battery voltage values of each battery cell 20 is transmitted to the control device 6.

[0024] The temperature sensors 32 provided on the battery pack 2 are positioned on the surface of the battery pack 2 and have the function of detecting the surface temperature of the battery pack; multiple sensors are used. In the example shown in Figure 1, three temperature sensors 32 are arranged at equal intervals along the direction of arrangement of the battery cells 20 of one battery pack 2.

[0025] The temperature sensor 32 can be, for example, a temperature-sensing element such as a thermistor. Each temperature sensor 32 is attached to the surface of the battery pack 2 by a suitable mounting means. A suitable adhesive can be used as the mounting means. Alternatively, a molding integration technique can be used in which the temperature-sensing element such as a thermistor is molded with a resin material and integrated with the battery pack 2. In the following description, the sensor will be attached to the battery pack 2 using the molding integration technique.

[0026] Thus, since the temperature sensor 32 has the function of detecting the surface temperature of the battery pack 2, it can be called a battery surface temperature sensor or battery temperature sensor. The temperature sensor 32 is connected to the I / V / T detection unit 41, and the surface temperature data of the battery pack 2 is transmitted to the control device 6 via this unit.

[0027] The intake air temperature sensor 34 has the function of detecting the ambient temperature around the battery pack 2 and is a temperature sensor installed at the intake port when the battery pack 2 is air-cooled. Since the intake air temperature sensor 34 has the function of acquiring the ambient temperature of the battery pack 2, it can also be called the ambient temperature acquisition unit. The temperature value data acquired by the intake air temperature sensor 34 is transmitted to the control device 6 via the I / V / T detection unit as intake air temperature 52 data. Hereafter, unless otherwise specified, ambient temperature refers to intake air temperature. Multiple intake air temperature sensors 34 may be installed at the intake port. In addition, another sensor may be provided as an ambient temperature detection means other than the intake air temperature sensor 34. In these cases, the detected values ​​of each sensor are averaged, and the result can be used as the ambient temperature of the battery pack 2.

[0028] The I / V / T detection unit 41 is an interface circuit provided between various sensors and the control device 6. The detected values ​​of the various sensors are, for example, analog voltage values. The I / V / T detection unit 41 has the function of converting the analog signal levels, which vary depending on the sensor, into standardized analog signals or digital signals suitable for various processing in the control device 6.

[0029] The cooling airflow input unit 42 is an interface circuit for inputting the cooling airflow value, which is the amount of air passing through the air intake when the battery pack 2 is air-cooled, to the control device 6. Specifically, the cooling airflow data indicated by the airflow switching switch or airflow setting button is acquired as an input value and transmitted to the control device 6.

[0030] The system main relay 10 is a power switch that can electrically connect or disconnect the battery pack 2, which is a high-voltage secondary battery, and the load side, which includes the rotating electric machine 18. To prevent terminal welding due to arc discharge etc. that occurs when high voltage is connected or disconnected, the system main relay 10 uses multiple relays, each independently provided on the positive busbar and the negative busbar. The timing of the connection and disconnection of these relays is set to be appropriately staggered relative to each other in order to prevent terminal welding.

[0031] The voltage converter 12 is a circuit positioned between the battery pack 2 and the inverter 16, and has a voltage conversion function. The voltage converter 12 can be configured to include a reactor and a switching element that operates under the control of the control device 6. The voltage conversion function includes a boost function that increases the voltage on the battery pack side using the energy storage function of the reactor and supplies it to the inverter side, and a step-down function that steps down the power from the inverter side and supplies it to the battery pack side as charging power.

[0032] The battery pack-side smoothing capacitor 11, located between the battery pack 2 and the voltage converter 12, and the inverter-side smoothing capacitor 14, located between the voltage converter 12 and the inverter 16, are capacitors that have the function of suppressing and smoothing fluctuations in voltage and current.

[0033] The inverter 16 is a circuit that performs power conversion between AC power and DC power. The inverter 16 is composed of multiple switching elements that operate under the control of the control device 6. The inverter 16 can perform both AC-DC conversion and DC-AC conversion. When the rotating electric machine 18 is used as a generator, the inverter 16 has an AC-DC conversion function that converts the AC three-phase regenerative power from the rotating electric machine 18 into DC power and supplies it to the battery pack as charging current. Furthermore, when the rotating electric machine 18 is used as a motor, when the vehicle is accelerating, the inverter 16 has an AC-DC conversion function that converts the DC power from the battery pack into AC three-phase drive power and supplies it to the rotating electric machine 18 as drive power. Conversely, when the vehicle is braking, the inverter 16 has an AC-DC conversion function that converts the AC three-phase regenerative power from the rotating electric machine 18 into DC power and supplies it to the battery pack as charging current.

[0034] Here, the battery pack 2, system main relay 10, battery pack-side smoothing capacitor 11, voltage converter 12, inverter-side smoothing capacitor 14, and inverter 16 are connected to the rotating electric machine 18 to form a single power supply circuit.

[0035] The rotating electric machine 18 is a motor-generator (MG) mounted on a vehicle, which functions as a motor when power is supplied from a power supply circuit including a battery pack 2, and as a generator when driven by an engine (not shown) or when the vehicle is being braked.

[0036] The control device 6 has the function of controlling the operation of each component of the battery system 1 as a whole. In particular, it has the function of limiting the input and output power of the battery pack 2 by estimating the maximum temperature inside the battery pack and controlling the operation of the voltage converter 12 and inverter 16 based on the estimated maximum temperature. Such a control device 6 can be configured with a computer or the like that is suitable for installation in a vehicle.

[0037] The control device 6 includes a maximum temperature estimation unit 60 that estimates the maximum temperature inside the battery pack 2, a temperature difference map storage unit 65 that stores the temperature difference map used in the maximum temperature estimation unit 60, and an input / output limiting unit 66 that limits the input / output power of the battery pack 2 based on the estimated maximum temperature.

[0038] The battery pack 2 can be charged using AC power or DC power by a charging device connected to a commercial power source. The control device 6 functions as a charging state determination means, for example, by communicating with the charging device to determine whether the current charging state is a fast charging state or not (for example, a non-charging state or a normal charging state).

[0039] Here, the temperature difference map storage unit 65 stores an overheat protection map, which is a map of offset temperature values ​​obtained for the temperature difference between the inside and outside of the battery with respect to the battery surface temperature, associated with at least one of the following: the intake air temperature data, which is the ambient temperature; the current load data, which is the current load data; and the cooling air volume data, which is input from the cooling air volume input unit 42 and obtained.

[0040] The maximum temperature estimation unit 60 includes an internal-external temperature difference estimation module 61 that estimates the internal-external temperature difference, which is the temperature difference between the surface temperature and the internal temperature of the battery pack 2; an R-induced temperature difference estimation module 62 that estimates the temperature difference within the battery pack due to differences in the internal resistance of each battery cell 20; a contact state-induced temperature difference estimation module 63 that estimates the temperature difference due to the contact state between the temperature sensor 32 and the battery pack 2; and a sensor-induced temperature difference estimation module 64 that estimates the temperature difference due to differences in detection characteristics among multiple temperature sensors 32.

[0041] Such functionality can be implemented by software, specifically by executing a battery pack input / output control program. A portion of this functionality may also be implemented in hardware.

[0042] The operation of this configuration, particularly the functions of the control device 6, will now be explained. Figure 2 is a flowchart showing the procedure for limiting the input and output of the battery pack 2 based on the estimation of the maximum internal temperature of the battery pack 2.

[0043] Figure 2 is a flowchart showing the procedure for limiting the input / output of the battery pack 2 based on the estimation of the maximum internal temperature of the battery pack 2, as described above. Each step corresponds to each processing step of the battery pack input / output limiting program. To limit the input / output of the battery pack 2, first, the intake air temperature, current load, cooling airflow rate, battery surface temperature, current I, voltage V, and rapid charging status are acquired (step S1). Specifically, the control device 6 acquires the intake air temperature 52, which is the ambient temperature, via the intake air temperature sensor 34, the battery surface temperature via the temperature sensor 32, the current value corresponding to the current load 51 via the current sensor 31, the battery voltage of the unit battery via the voltage sensor 33, and the cooling airflow rate data from the cooling airflow input unit 42. The control device 6 also acquires information from the charging device regarding whether the battery pack 2 is in a rapid charging state (rapid charging in progress).

[0044] Next, four temperature differences are estimated. Specifically, the internal-external temperature difference is estimated (step S2), the R-induced temperature difference is estimated (step S7), the sensor contact state-induced temperature difference is estimated (step S8), and the sensor-induced temperature difference is estimated (step S9).

[0045] The internal-to-external temperature difference estimation (step S2) is a process of estimating the internal-to-external temperature difference of the battery, which is the difference between the internal temperature of the battery pack 2 and the battery surface temperature actually detected by the temperature sensor 32, according to the ambient temperature. This process is performed by the function of the internal-to-external temperature difference estimation module 61 in the maximum temperature estimation unit 60 of the control device 6. The internal-to-external temperature difference estimation module 61 is an estimation means for estimating the internal-to-external temperature difference of the battery pack 2.

[0046] Specifically, the temperature difference, which is the difference between the battery surface temperature actually detected by the temperature sensor 32 and the internal temperature of the battery pack 2, is estimated by considering the intake air temperature 52 data, which is the ambient temperature acquired via the intake air temperature sensor 34, the current load 51 data, which is acquired via the current sensor 31, and the cooling air volume data, which is acquired via the cooling air volume input unit 42. In order to accurately estimate the temperature difference, it is preferable to consider all of the intake air temperature 52 data, current load 51 data, and cooling air volume data, but if there is sufficient capacity in the input / output limits of the battery pack 2, for example, only the intake air temperature 52 data may be used. Alternatively, the intake air temperature 52 data and the current load 51 data may be considered.

[0047] For estimating the internal-external temperature difference, a map showing the relationship between the factors considered above and the internal-external temperature difference can be used. For example, Figure 3 is a map showing the relationship between ambient temperature and internal-external temperature difference in a battery system 1 according to an embodiment, with the intake air temperature 52 as the ambient temperature. A map showing the relationship between ambient temperature and internal-external temperature difference, such as the one shown in Figure 3, can be used by reading a map stored in the temperature difference map storage unit 65. This map is a mapping of data obtained in advance through experiments, etc., with ambient temperature on the horizontal axis and the internal-external temperature difference based on the battery surface temperature on the vertical axis, i.e., internal-external temperature difference = (internal temperature of battery pack 2) - (battery surface temperature measured by temperature sensor 32).

[0048] The temperature difference between the inside and outside of the device increases as the ambient temperature decreases from room temperature (RT). This characteristic is determined by the structure of the battery pack 2 and can therefore be determined in advance. The map of the determined ambient temperature and the temperature difference between the inside and outside of the device is stored in the temperature difference map storage unit 65 of the control device 6. Therefore, to estimate the temperature difference between the inside and outside of the device, for example, the ambient temperature can be used as a search key to search the map showing the relationship between the ambient temperature and the temperature difference between the inside and outside of the device, and the corresponding temperature difference can be read out.

[0049] Furthermore, in the battery system 1 according to this embodiment, there are two maps showing the relationship between ambient temperature and the internal-external temperature difference: an internal-external temperature difference map for rapid charging used during rapid charging of the battery pack 2, and a normal internal-external temperature difference map used when the battery pack 2 is not being rapidly charged. The internal-external temperature difference map for rapid charging and the normal internal-external temperature difference map are stored in the temperature difference map storage unit 65 of the control device 6. The internal-external temperature difference estimation module 61 switches the map (information) used to estimate the internal-external temperature difference according to the determination result of whether or not rapid charging is in progress.

[0050] Furthermore, the map showing the relationship between ambient temperature and the temperature difference between the inside and outside may be in a format other than a map, as long as it associates ambient temperature with the temperature difference between the inside and outside. For example, it may be in the form of a lookup table that tables the relationship between ambient temperature and the temperature difference between the inside and outside, or it may be in the form of a function that takes ambient temperature as input and outputs the temperature difference between the inside and outside.

[0051] In Figure 2, the internal-to-external temperature difference estimation module 61 determines whether or not rapid charging is in progress (step S3) during the internal-to-external temperature difference estimation (step S2). If the internal-to-external temperature difference estimation module 61 determines that rapid charging is in progress (Yes in step S3), it selects an internal-to-external temperature difference map for rapid charging (step S4). The internal-to-external temperature difference estimation module 61 then decides that the map to be used for internal-to-external temperature difference estimation is the internal-to-external temperature difference map for rapid charging (step S6). On the other hand, if the internal-to-external temperature difference estimation module 61 determines that rapid charging is not in progress (No in step S3), it selects a normal internal-to-external temperature difference map (step S5). The internal-to-external temperature difference estimation module 61 then decides that the map to be used for internal-to-external temperature difference estimation is the normal internal-to-external temperature difference map (step S6). Using the internal-to-external temperature difference map determined in step S6, the internal-to-external temperature difference estimation module 61 estimates the internal-to-external temperature difference.

[0052] The R-induced temperature difference estimation (step S7) is a process of estimating the internal resistance R of each battery cell 20 from the voltage V and current I of each battery cell 20 at multiple placement locations, and estimating the temperature difference within the battery pack 2 caused by the difference in the internal resistance R of each battery cell 20. This process is performed by the function of the R-induced temperature difference estimation module 62 of the maximum temperature estimation unit 60.

[0053] The sensor contact state-induced temperature difference estimation (step S8) is a process of estimating in advance the maximum value of the deviation between the actual surface temperature of the battery pack 2 and the detected value of each temperature sensor 32, which occurs due to the contact state between the multiple temperature sensors 32 and the surface of the battery pack 2. This process is performed by the contact state-induced temperature difference estimation module 63 of the maximum temperature estimation unit 60.

[0054] After the four temperature difference estimation processes are completed, the maximum temperature estimation unit 60 then estimates the maximum temperature inside the battery pack (step S10). The maximum temperature estimation unit 60 then determines whether the estimated maximum temperature is above a predetermined threshold temperature (step S11). Preferably, the smoke emission temperature T0, which is a characteristic of lithium-ion batteries, is used as the threshold temperature. If the battery pack 2 is not a lithium-ion battery, the threshold temperature set according to the characteristics of that battery type can be used as T0. If the determination in step S11 is affirmative, the input / output control unit of the control device 6 limits the input / output power of the battery pack 2 to prevent smoke emission (step S12). If step S12 is executed, or if the determination in step S11 is denied, the series of battery pack input / output control processes ends.

[0055] The battery system 1 according to this embodiment can estimate the internal and external temperature difference in accordance with the rapid charging process when the internal and external temperature difference is small, thereby suppressing unnecessary input / output restrictions. [Explanation of Symbols]

[0056] 1. Battery System 2 Battery Packs 6. Control device 10 System Main Relays 11. Smoothing capacitor on the battery pack side 12 Voltage Converters 14. Inverter-side smoothing capacitor 16 Inverters 18 Rotating Electric Machines 20 battery cells 31 Current Sensor 32 Temperature Sensors 33 Voltage Sensor 34. Intake air temperature sensor 41 I / V / T detection unit 42 Cooling airflow input section 60 Maximum temperature estimation part 61. Module for estimating the temperature difference between inside and outside the building. 62 R-induced temperature difference estimation module 63 Contact-Induced Temperature Difference Estimation Module 64 Sensor-Induced Temperature Difference Estimation Module 65 Temperature difference map memory unit 66 Input / Output Limiting Section

Claims

1. A charging state determination means for determining whether the current charging state is a fast charging state or not, An estimation means for estimating the temperature difference between the inside and outside of the battery pack, A control means for limiting the input / output of the battery pack according to the estimation result of the estimation means, A battery system equipped with, The battery system is characterized in that the estimation means switches the information used for estimation depending on whether the determination result by the charging state determination means is a rapid charging state or not.

2. The information used by the estimation means for estimation is a map showing the relationship between ambient temperature and the temperature difference between the inside and outside, The battery system according to claim 1, characterized in that the map includes an internal-to-external temperature difference map for use during rapid charging of the battery pack, and a normal internal-to-external temperature difference map for use when the battery pack is not being rapidly charged.

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