Battery charging system and charging method

Abstract

To shorten a charging time while suppressing the occurrence of problems associated with changing a target temperature of a battery according to the output power of an external power supply when charging the battery using the external power supply.SOLUTION: A charging system includes a battery that can be charged using an external power source, a heater that heats the battery, and a control device that controls the operation of the heater. The control device acquires an actual temperature of the battery and an output power of the external power source, sets a target temperature of the battery based on the output power, and drives the heater when the actual temperature is lower than the target temperature while the battery is being charged using the external power source. The control device further compares a current value of the output power with a previous value of the output power while the battery is being charged using the external power source, and updates the target temperature based on the current value if the current value exceeds the previous value, and maintains the target temperature at the current value when the current value does not exceed the previous value.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a system and method for charging a battery using an external power source.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2023-102958 discloses a battery system capable of charging (external charging) using an external power source. In this conventional system, while the temperature of the battery during external charging is lower than the reference temperature, drive control of a heater for raising the temperature of this battery is performed. However, for driving the heater, power from the battery during external charging is used. Therefore, in the conventional system, during drive control of the heater, the power supplied from the external power source to the battery and the minimum value of the power consumed by the heater are compared. And when the supply power from the external power source is smaller than the minimum value of the power consumed by the heater, the heater is driven intermittently.

[0003] Examples of documents showing the technical level of the technical field related to the present disclosure include Japanese Unexamined Patent Application Publication No. 2023-102958, Japanese Unexamined Patent Application Publication No. 2016-110957, and Japanese Unexamined Patent Application Publication No. 11-341698.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] External power supplies include those whose output power fluctuates according to the power consumption in homes and various facilities. This disclosure considers the drive control of a heater during battery charging using such an external power supply. In this case, in order to shorten the charging time, it is desirable to change the target temperature of the battery in the heater drive control according to the output power. For example, the target temperature is lowered when the output power is low, and raised when the output power is high. By changing the target temperature in this way, it is possible to reduce the power consumption by the heater when the output power is low, and shorten the charging time by raising the temperature of the battery when the output power is high.

[0006] However, if the target temperature is changed according to the output power, the actual battery temperature may fluctuate above the target temperature. When the actual temperature fluctuates above the target temperature, it is expected that the heater will repeatedly stop and restart. As a result, when the total number of times the heater stops and restarts increases, components such as relays will wear out more easily. Therefore, when changing the target temperature according to the output power, improvements are desirable from the perspective of suppressing the occurrence of malfunctions associated with this change.

[0007] One of the purposes of this disclosure is to provide a technology that can shorten the charging time when charging a battery using an external power source, while suppressing the occurrence of malfunctions caused by changes in the target temperature of the battery in accordance with the output power of the external power source. [Means for solving the problem]

[0008] The first aspect of this disclosure is a battery charging system, which has the following features: The charging system comprises a battery that can be charged using an external power source, a heater that raises the temperature of the battery, and a control device that controls the operation of the heater. The control device acquires the actual temperature of the battery and the output power of the external power supply, sets a target temperature for the battery based on the output power, and drives the heater when the actual temperature is lower than the target temperature while the battery is being charged using the external power supply. The control device further compares the current output power with the previous output power while the battery is being charged using the external power supply. If the current output power exceeds the previous output power, it updates the target temperature based on the current output power. If the current output power does not exceed the previous output power, it maintains the target temperature at the current value.

[0009] The second aspect of this disclosure is a method for charging a battery, which has the following features: The method includes the steps of: obtaining the actual temperature of a battery that can be charged using an external power source and the output power of the external power source; setting a target temperature of the battery based on the output power; driving a heater to raise the temperature of the battery when the actual temperature is lower than the target temperature while the battery is being charged using the external power source; comparing the current value of the output power with the previous value of the output power while the battery is being charged using the external power source; updating the target temperature based on the current value if the current value exceeds the previous value; and maintaining the target temperature at the current value if the current value does not exceed the previous value. [Effects of the Invention]

[0010] According to this disclosure, during battery charging using an external power supply, the current output power of the external power supply is compared with the previous output power. If the current value exceeds the previous value, the target temperature of the battery is updated based on the current value. On the other hand, if the current value does not exceed the previous value, the target temperature is maintained at the current value. In other words, the target temperature is updated only when the current value exceeds the previous value. Therefore, compared to a system where the target temperature is updated every time the output power fluctuates, it is possible to reduce the total number of times the heater is stopped and restarted after such stops. Furthermore, by updating the target temperature based on the current value which exceeds the previous value, it is possible to set the updated target temperature higher than the target temperature before the update. Therefore, it is possible to shorten the charging time. [Brief explanation of the drawing]

[0011] [Figure 1]This figure illustrates a configuration particularly relevant to a charging system according to an embodiment of the present disclosure. [Figure 2] This diagram illustrates the overview of heater drive control performed during battery charging using an external power source, and the characteristics of the embodiment. [Figure 3] This flowchart shows the process flow for heater drive control, which is particularly relevant to the embodiment. [Figure 4] This diagram illustrates a second example of heater drive control. [Figure 5] This diagram illustrates a third example of heater drive control. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure will be described below with reference to the drawings. However, structures and the like described in the embodiments below are not necessarily essential to this disclosure unless specifically stated or clearly defined in principle.

[0013] 1. Battery charging system The battery charging system according to the embodiment is mounted on a vehicle, for example. The vehicle is one that can be plugged in and charged using power supplied from an external power source located outside the vehicle. Examples of such vehicles include plug-in hybrid vehicles (PHVs) and plug-in hybrid electric vehicles (PHEVs).

[0014] Figure 1 is a diagram illustrating a configuration particularly relevant to the charging system according to the embodiment. Figure 1 shows an external power supply 10, a charging system 20, and a motor 30. The external power supply 10 is, for example, a household single-phase 100V AC power supply or a single-phase 200V AC power supply. The external power supply 10 includes a connector 11.

[0015] The charging system 20 corresponds to the configuration of the battery charging system according to the embodiment. The charging system 20 includes a charging lid 21, a power line 22, a buck-boost unit 23, a battery 24, a heater 25, a control device 26, and a temperature sensor 27.

[0016] The charging lid 21 is the part where the connector 11 is inserted. The power line 22 connects the charging lid 21 and the buck-boost unit 23. The power line 22 also connects the charging lid 21 and the heater 25. The power line 22 supplies the power received from the external power source 10 through the connector 11 to the buck-boost unit 23 and the heater 25 respectively.

[0017] The buck-boost unit 23 is a device for charging the battery 24. For example, the buck-boost unit 23 includes, for example, a buck-boost converter (not shown) and various relays (not shown). The buck-boost converter boosts the power supplied from the external power source 10 based on the control signal from the control device 26. The various relays operate based on the control signal from the control device 26 and supply the power boosted by the buck-boost converter to the battery 24.

[0018] The battery 24 is a power storage device for driving the motor 30. The battery 24 is composed of a secondary battery such as a nickel-hydrogen battery or a lithium-ion battery. For example, the battery 24 is composed of a stack in which a plurality of battery cells of about 1 to 5V are stacked.

[0019] The heater 25 is a device that generates Joule heat due to electric resistance by being energized to heat the battery 24, thereby raising the temperature of the battery 24. The temperature (actual temperature AT) of the heater 25 is measured by the temperature sensor 27 attached to the battery 24. The information on the actual temperature AT measured by the temperature sensor 27 is output to the control device 26.

[0020] The control device 26 is a computer that performs various controls in a vehicle equipped with a charging system 20. The control device 26 includes computer hardware such as a processor and memory, and operates according to the installed software such as an OS (Operating System) and application programs. The various controls performed by the control device 26 include drive control of the heater 25. Drive control of the heater 25 includes control performed during plug-in charging of the battery 24 using an external power supply 10, and control performed during the operation of the motor 30. The former drive control is performed from the viewpoint of charging efficiency, and the latter drive control is performed from the viewpoint of discharge efficiency. In this embodiment, we will focus on the former drive control.

[0021] Motor 30 drives the vehicle equipped with the charging system 20. Power is supplied to motor 30 from battery 24. Motor 30 converts the power supplied from battery 24 into rotational energy to rotate the wheels. Note that multiple motors 30 may be provided.

[0022] 2. Heater drive control Figure 2 illustrates the overview of the drive control of the heater 25 performed during plug-in charging of the battery 24 using an external power supply 10, and the features of the embodiment. This drive control of the heater 25 is performed when the actual temperature AT is lower than the target temperature TT of the battery 24.

[0023] In this embodiment, the target temperature TT is set based on the output power OP of the external power supply 10 in order to shorten the charging time of the battery 24. For example, the target temperature TT is set to a higher temperature as the output power OP increases. When the target temperature TT is set to a high temperature, the actual temperature AT rises in a shorter time. Therefore, it becomes possible to shorten the charging time as the charging efficiency increases. On the other hand, when the target temperature TT is set to a low temperature, it becomes possible to reduce the power consumption by the heater.

[0024] In the example shown in FIG. 2, threshold values TH1 and TH2 for setting the target temperature of the battery based on the grid power (output power of the external power supply) are set. In this example, the target temperature is set by comparing the grid power with the threshold values TH1 and TH2. For example, when the grid power is smaller than the threshold value TH1, the target temperature is set to the temperature TT1. Also, when the grid power is larger than the threshold value TH2, the target temperature is set to the temperature TT2 (TT2 > TT1). Further, when the grid power is between the threshold values TH1 and TH2, the target temperature is set to the temperature TT3 (TT2 > TT3 > TT1).

[0025] In the example shown in FIG. 2, the grid power generally changes between the threshold values TH1 and TH2. However, this example includes a time period when the grid power is smaller than the threshold value TH1 and a time period when the grid power is larger than the threshold value TH2. In the time period when the grid power is smaller than the threshold value TH1, the target temperature is changed from the temperature TT3 to the temperature TT1 (TT1 < TT3). In the time period when the grid power is larger than the threshold value TH2, the target temperature is changed from the temperature TT3 to the temperature TT2 (TT2 > TT3).

[0026] When such a change in the target temperature is made, there is a possibility that the magnitude relationship between the target temperature and the actual temperature of the battery may reverse before and after the change in the target temperature. If the magnitude relationship reverses, it may affect the execution of the drive control of the heater. In the example shown in FIG. 2, the drive of the heater is stopped (from ON to OFF) after the grid power decreases and falls below the threshold value TH1 and after the grid power decreases and falls below the threshold value TH2. Also, the drive of the heater is restarted (from OFF to ON) after the grid power increases and exceeds the threshold value TH1 and after the grid power increases and exceeds the threshold value TH2.

[0027] Even if the target temperature is not changed, the heater will repeatedly stop and restart depending on the relationship between the target temperature and the actual battery temperature. However, if the target temperature is changed, the heater is expected to stop and restart more frequently than in the case where it is not changed. As a result, components such as relays will wear out more easily when the total number of times the heater stops and restarts.

[0028] Therefore, in this embodiment, the target temperature TT is updated only when the output power OP increases during plug-in charging of the battery 24 using the external power supply 10. In the example already described, the target temperature TT is set to a higher temperature as the output power OP increases. Therefore, updating the target temperature TT only when the output power OP increases means that the update of the target temperature TT is permitted only when changing to a higher temperature. Consequently, it is possible to reduce the total number of times the drive is stopped and restarted compared to when the target temperature TT is changed to a higher temperature and when it is changed to a lower temperature. In addition, it is possible to shorten the charging time by changing the target temperature TT to a higher temperature.

[0029] 3. Processing Example Figure 3 is a flowchart showing the processing flow for drive control of the heater 25, which is particularly relevant to this embodiment. The routine shown in Figure 3 is repeatedly executed by the processor of the control unit 26, for example, while the connector 11 is inserted into the charging lid 21 (i.e., during plugging in).

[0030] The routine shown in Figure 3 first acquires the output power OP and the actual temperature AT (step S11). The output power OP information may be obtained from the external power supply 10 or from the step-up / step-down unit 23. The actual temperature AT information is obtained from the temperature sensor 27.

[0031] Following the processing in step S11, it is determined whether the current value OP(k) of the output power OP is greater than the previous value OP(k-1) (step S12). The current value OP(k) is the latest value of the output power OP obtained in the processing of step S11. The previous value OP(k-1) is, for example, a past value of the output power OP obtained in the processing of step S11 of the previous routine. In another example, the previous value OP(k-1) is the output power OP obtained in the history of the output power OP at a predetermined time before the acquisition time of the current value OP(k).

[0032] If the result of step S12 is positive, steps S13 and S14 are performed. Otherwise, steps S13 and S14 are skipped and step S15 is performed. Note that in step S12, a simple comparison of the current value OP(k) and the previous value (k-1) may be performed, or a predetermined margin may be added to the previous value (k-1) before comparing it with the current value (k) in order to detect a significant increase in output power OP while allowing for some fluctuation in output power OP. Also, immediately after plugging in, the previous value (k-1) does not exist. Therefore, in this case, steps S13 and S14 are performed exceptionally.

[0033] In step S13, the target temperature TT is set. The target temperature TT is set to a higher temperature as the output power OP increases. In step S14, the target temperature TT is updated using the latest target temperature TT set in step S13. If steps S13 and S14 are not performed, the target temperature TT is not updated. In this case, the current value of the target temperature TT is maintained. The current value of the target temperature TT is the value set in step S13 prior to the last routine.

[0034] In step S15, it is determined whether or not the heater 25 is running. If the result of the determination in step S15 is positive, the process in step S16 is performed. Otherwise, the process in step S17 is performed.

[0035] In steps S16 and S17, the target temperature TT and the actual temperature AT are compared, respectively. The target temperature TT is the latest value of the target temperature TT. The actual temperature AT is the latest value of the actual temperature AT obtained in step S11. In step S16, it is determined whether the actual temperature AT is greater than or equal to the target temperature TT. In step S17, it is determined whether the actual temperature AT is less than the target temperature TT. If the result of step S16 is positive, and the result of step S17 is negative, the heater 25 is stopped (step S18). If the result of step S16 is negative, and the result of step S17 is positive, the heater 25 is driven (step S19).

[0036] 4. Another processing example In this embodiment, a part of the processing example (first processing example) described in Figure 3 can be modified. Figure 4 is a diagram illustrating a second processing example of heater drive control. Figure 5 is a diagram illustrating a third processing example of heater drive control.

[0037] In the second processing example shown in Figure 4, the output power OP at the start of charging (time t0) is set to the reference value OPref. Then, during plug-in charging, it is determined whether the current value OP(k) exceeds the reference value OPref. This determination is performed, for example, following the process in step S11 in Figure 3. If it is determined that the current value OP(k) exceeds the reference value OPref, the process in step S12 is performed; otherwise, the process in step S15 in Figure 3 is performed.

[0038] If the determination of whether the current value OP(k) exceeds the reference value OPref is performed following the process in step S11 of Figure 3, the following effect can be expected. That is, if the output power OP is large at the start of charging, it is expected that the output power OP will temporarily decrease during plug-in charging (time t1 or t3 in Figure 4). However, if the above determination is performed during the time period when the output power OP increases following this temporary decrease (for example, the time period before time t2 or t4 in Figure 4), the processes in steps S12 to S14 of Figure 3 can be skipped.

[0039] In an embodiment where the target temperature TT is set to a higher temperature as the output power OP increases, when an increase in output power OP occurs following a temporary decrease, the target temperature TT will not be set higher than the current value. In this regard, by performing the above determination, it is possible to avoid setting and updating the target temperature TT to a lower value than the current value (i.e., the processing in steps S13 and S14 in Figure 3), and to maintain the current value of the target temperature TT.

[0040] In the third processing example shown in Figure 5, the maximum value OPmax of the output power OP from the start of charging to the present is recorded. Then, during plug-in charging, it is determined whether the current value OP(k) exceeds the maximum value OPmax. This determination is performed, for example, following the process in step S11 in Figure 3. If it is determined that the current value OP(k) exceeds the maximum value OPmax, the process in step S12 is performed; otherwise, the process in step S15 in Figure 3 is performed.

[0041] If the determination of whether the current value OP(k) exceeds the maximum value OPmax is performed following the process in step S11 of Figure 3, the following effect can be expected. That is, if the output power OP is small at the start of charging, it is expected that the output power OP will temporarily increase during plug-in charging (times t5 to t6 and t7 to t8 in Figure 5). Therefore, by performing the above determination during this period of increased output power OP, it becomes possible to set and update a target temperature TT higher than the current value (i.e., the processes in steps S13 and S14 of Figure 3).

[0042] In an embodiment where the target temperature TT is set to a higher temperature as the output power OP increases, a target temperature TT higher than the current value will not be set unless the output power OP exceeds the maximum value OPmax from the start of charging to the present. In this regard, by performing the above determination, if the output power OP exceeds the maximum value OPmax from the start of charging to the present, the target temperature TT can be reliably set and updated based on the latest maximum value OPmax. Otherwise, the target temperature TT set based on the output power OP, which is the maximum value OPmax from the start of charging to the present, can be maintained. [Explanation of symbols]

[0043] 10…External power supply, 11…Connector, 20…Charging system, 21…Charging lid, 22…Power line, 23…Step-up / step-down unit, 24…Battery, 25…Heater, 26…Control unit, 27…Temperature sensor, 30…Motor, AT…Actual temperature, OP…Output power, OP(k)…Current value, OP(k-1)…Previous value, OPmax…Maximum value, OPref…Reference value, TT…Target temperature

Claims

1. A battery that can be charged using an external power source, A heater for raising the temperature of the aforementioned battery, A control device for controlling the drive of the heater, Equipped with, The control device is The actual temperature of the battery and the output power of the external power supply are obtained. Based on the output power, the target temperature of the battery is set. During charging of the battery using the external power supply, the heater is driven if the actual temperature is lower than the target temperature. The control device further, During the charging of the battery using the external power supply, the current value of the output power is compared with the previous value of the output power. If the current value exceeds the previous value, the target temperature is updated based on the current value; if the current value does not exceed the previous value, the target temperature is maintained at the current value. A battery charging system characterized by the following.

2. The control device further, The output power value at the start of charging the battery using the external power supply is set to a reference value. The current value is compared with the reference value, If the current value exceeds the reference value, a comparison is made between the current value and the previous value. A battery charging system according to feature 1.

3. The control device further, The maximum output power is recorded from the start of charging the battery using the external power supply. The current value is compared with the maximum value, If the current value exceeds the maximum value, a comparison is made between the current value and the previous value. The charging system according to claim 1.

4. The steps include obtaining the actual temperature of a battery that can be charged using an external power supply and the output power of the external power supply, The steps include setting a target temperature for the battery based on the output power, The steps include: driving a heater to raise the temperature of the battery when the actual temperature is lower than the target temperature while the battery is being charged using the external power supply; During the charging of the battery using the external power supply, the step of comparing the current value of the output power with the previous value of the output power, If the current value exceeds the previous value, the target temperature is updated based on the current value; if the current value does not exceed the previous value, the target temperature is maintained at the current value. A method for charging a battery, characterized by including [a certain element].

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