Solar charging system

Abstract

To inhibit actually usable electric energy from reducing in a charge cycle of a battery.SOLUTION: A solar charging system comprises a first battery 40 for storing power generated by a solar panel 10, a second battery 50 for storing power supplied from the first battery 40, and a controller 21. The controller 21 charges the second battery 50 by performing power supply from the first battery 40 to the second battery 50 when a charging rate of the first battery 40 becomes equal to or larger than an upper limit and stops the power supply from the first battery 40 to the second battery 50 to charge the first battery 40 when the charging rate of the first battery 40 becomes equal to or smaller than a lower limit. The controller 21 executes change processing of extending a use range, which is a range from the upper limit to the lower limit, in the case that the degree of deterioration of the first battery 40 is high as compared with that in the case that the degree of deterioration is low.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a solar charging system.

Background Art

[0002] The solar charging system described in Patent Document 1 includes a solar panel, a first battery, a second battery, and a control device that controls the charging of the first battery and the second battery. The first battery stores the electric power generated by the solar panel. The second battery stores the electric power supplied from the first battery. When the charging rate of the first battery reaches or exceeds a predetermined upper limit value, this control device supplies electric power from the first battery to the second battery to charge the second battery. Further, when the charging rate of the first battery reaches or falls below a predetermined lower limit value along with the supply of electric power to the second battery, this control device stops the supply of electric power from the first battery to the second battery and charges the first battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The full charge capacity of the battery gradually decreases due to deterioration. Therefore, when the range from the above-mentioned upper limit value to the lower limit value is used as the usage range, as the deterioration of the battery progresses, the capacity range of the battery in that usage range becomes narrower. Accordingly, the amount of electric power that can actually be used in the charging cycle of the first battery that repeats charging and discharging decreases.

Means for Solving the Problems

[0005] A solar charging system for solving the above problems comprises a solar panel, a first battery for storing electricity generated by the solar panel, a second battery for storing electricity supplied from the first battery, and a control device. The control device performs a process to charge the second battery by supplying power from the first battery to the second battery when the charge level of the first battery exceeds a predetermined upper limit, and stops supplying power from the first battery to the second battery and charges the first battery when the charge level of the first battery falls below a predetermined lower limit. When the range from the upper limit to the lower limit is defined as the usage range, the control device performs a modification process to change the usage range so that it is wider than when the degradation level is low, if the degradation level of the first battery is high. [Effects of the Invention]

[0006] This helps to minimize the decrease in the amount of usable power during the battery charging cycle. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram of the solar charging system. [Figure 2] Figure 2 is a graph showing the change in the capacity of the first battery. [Figure 3] Figure 3 is a flowchart showing the steps of the process performed by the control device. [Figure 4] Figure 4 is a graph showing how the upper and lower limits are set in the example of the changes. [Modes for carrying out the invention]

[0008] <Outline configuration of a solar charging system> An embodiment of the solar charging system will be described below with reference to Figures 1 and 2. The solar charging system of this embodiment is mounted on a vehicle.

[0009] As shown in Figure 1, the solar charging system 100 includes a solar panel 10, a control unit 20, a battery monitoring unit 30, a first battery 40, a second battery 50, a relay 60, and a third converter 70.

[0010] The solar panel 10 is constructed by arranging multiple solar cells, which generate electricity from sunlight, in a panel-like configuration. The solar panel 10 is installed, for example, on the roof of a vehicle VC.

[0011] The control unit 20 includes a control device 21, a first converter 25, and a second converter 26. The control device 21 includes a CPU and a memory device. The CPU of the control device 21 executes various controls, such as power generation control of the solar panel 10, charging control of the first battery 40, and charging control of the second battery 50, by executing a program stored in the memory device of the control device 21. The first converter 25 is a DC-DC converter that converts the power generated by the solar panel 10. The second converter 26 is a DC-DC converter that converts the power converted by the first converter 25 and supplies it to the first battery 40.

[0012] The third converter 70 is a DC-DC converter that converts the power stored in the first battery 40 and the power generated by the solar panel 10 and supplies them to the second battery 50. The control device 21 controls the driving of the first converter 25, the second converter 26, and the third converter 70.

[0013] The battery monitoring unit 30 includes a battery control device 31. The battery control device 31 includes a CPU and a memory device. The CPU of the battery control device 31 executes a program stored in the memory device of the battery control device 31 to monitor the state of the second battery 50 and to control the opening and closing of the relay 60 for charging the second battery 50. The battery control device 31 is connected to the control device 21 so as to be able to communicate with each other. The battery control device 31 transmits the state of the second battery 50, such as input current, output current, voltage, and temperature, detected by sensors, to the control device 21. The control device 21 transmits an opening and closing instruction signal for the relay 60 to the battery control device 31.

[0014] The first battery 40 is a secondary battery that charges with electricity generated by the solar panel 10, and is, for example, a lithium-ion battery. The first battery 40 is not limited to a lithium-ion battery and may be of other types. The first battery 40 is an auxiliary battery that supplies power to the auxiliary equipment of the vehicle VC. The auxiliary equipment of the vehicle VC is, for example, an electric oil pump, a navigation system, lamps, and various sensors. The control device 21 acquires the state of the first battery 40 detected by sensors, i.e., input current, output current, voltage, temperature, etc. Based on the acquired data, the control device 21 calculates the current amount of charge stored in the first battery 40, the capacity CH, the current full charge capacity CHmax of the first battery 40, and the charge level SOC of the first battery 40. The charge level SOC is the value obtained by dividing the full charge capacity CHmax by the capacity CH.

[0015] The second battery 50 is a secondary battery that charges the power converted by the third converter 70, that is, the power stored in the first battery 40 or the power generated by the solar panel 10, and is, for example, a lithium-ion battery. The first battery 40 is not limited to a lithium-ion battery and may be of other types. The second battery 50 is a drive battery that supplies power to the motor that drives the vehicle VC.

[0016] Relay 60 is located in the circuit between the third converter 70 and the second battery 50. When relay 60 is closed, power is exchanged between the third converter 70 and the second battery 50. When relay 60 is opened, the exchange of power between the third converter 70 and the second battery 50 is interrupted.

[0017] <Regarding the charging process performed by the control device 21> The control device 21 acquires the state of charge (SOC) of the first battery 40 at predetermined intervals. When the SOC reaches or exceeds a predetermined upper limit (SOCH), the control device 21 supplies power from the first battery 40 to the second battery 50 to charge the second battery 50. Furthermore, when the SOC of the first battery 40 falls below a predetermined lower limit (SOCL) due to the power supply to the second battery 50, the control device 21 stops supplying power from the first battery 40 to the second battery 50. The control device 21 then charges the first battery 40 using the power generated by the solar panel 10. The control device 21 repeatedly performs this charging cycle for the first battery 40 while the solar charging system 100 is running. The upper limit (SOCH) is predetermined to be a value that is a predetermined value less than the value at which the first battery 40 becomes overcharged. The lower limit (SOCL) is predetermined to be a value that is a predetermined value greater than the value at which the first battery 40 becomes over-discharged.

[0018] <Regarding the change processing performed by the control device 21> The full charge capacity CHmax of the first battery 40 gradually decreases due to the deterioration of the first battery 40. Therefore, when the range from the above-mentioned upper limit value SOCH to the lower limit value SOCL is defined as the usage range UR, as the deterioration of the first battery 40 progresses, the capacity range CHR of the first battery 40 within the usage range UR becomes narrower. Consequently, the amount of electric energy EE that can actually be used in the charge cycle of the first battery 40, which repeatedly charges and discharges, decreases. Note that the capacity CH of the first battery 40 when the state of charge SOC of the first battery 40 is equal to the upper limit value SOCH is set as the maximum value of the capacity range CHR, and the capacity CH of the first battery 40 when the state of charge SOC is equal to the lower limit value SOCL is set as the minimum value of the capacity range CHR. At this time, the amount of electric energy EE is equal to the value obtained by subtracting the minimum value of the capacity range CHR from the maximum value of the capacity range CHR.

[0019] FIG. 2 shows the capacity A of the non-deteriorated first battery 40 and the capacity B of the deteriorated first battery 40. As shown in this FIG. 2, the full charge capacity CHmaxb of the deteriorated first battery 40 is less than the full charge capacity CHmaxa of the non-deteriorated first battery 40. Therefore, even if the upper limit value SOCH and the lower limit value SOCL are the same and the usage range UR is the same, the capacity range CHRb of the deteriorated first battery 40 is narrower than the capacity range CHRa of the non-deteriorated first battery 40. Consequently, the amount of electric energy EEb that the deteriorated first battery 40 can actually use in the charge cycle of the first battery 40 decreases compared to the amount of electric energy EEa that the non-deteriorated first battery 40 can actually use.

[0020] When the amount of electric energy EE that can actually be used decreases in this way, the cycle of the charge cycle of the first battery 40 becomes shorter. Therefore, there is a risk that the deterioration of the first battery 40 and the deterioration of the circuit that switches the charge and discharge of the first battery 40 will progress. Also, when the cycle of the charge cycle of the first battery 40 becomes shorter, there is a risk that the cycle of the charge cycle of the second battery 50, which uses the power of the first battery 40, will also become shorter. Therefore, there is also a risk that the deterioration of the second battery 50 and the deterioration of the circuit that switches the charge and discharge of the second battery 50 will progress.

[0021] Therefore, when the degree of deterioration of the first battery 40 is high, the control device 21 executes a change process for changing the use range UR so that the use range UR becomes wider than when the degree of deterioration is low. By executing this change process, it is possible to suppress a decrease in the amount of power EE that can actually be used in the charging cycle of the first battery 40.

[0022] FIG. 3 shows the procedure of the process executed by the control device 21 to execute the change process. The control device 21 executes this process at every predetermined cycle during the operation of the solar charging system 100. In the following, the step numbers of each process are represented by numbers preceded by "S".

[0023] When starting this process, the control device 21 acquires the current fully charged capacity CHmax of the first battery 40 (S100). Next, the control device 21 determines whether or not the acquired fully charged capacity CHmax is less than or equal to the threshold value CHmaxref (S110). As the deterioration of the first battery 40 progresses and its degree of deterioration increases, the fully charged capacity CHmax decreases. Therefore, the fully charged capacity CHmax is a value indicating the degree of deterioration of the first battery 40. The threshold value CHmaxref is a value for determining that the degree of deterioration of the first battery 40 has become high enough to widen the use range UR based on the fact that the fully charged capacity CHmax is less than or equal to the threshold value CHmaxref, and is an appropriate value.

[0024] Then, in the process of S110, if the control device 21 determines that the full charge capacity CHmax is less than or equal to the threshold CHmaxref (S110: YES), the control device 21 executes a modification process to change both the upper limit SOCH and the lower limit SOCL (S120). In this modification process, the control device 21 executes a process to set the new upper limit SOCH as the value obtained by adding a default value α to the currently set upper limit SOCH. The default value α is a value that can suppress overcharging of the first battery 40. Also, in the process of S120, the control device 21 executes a process to set the new lower limit SOCL as the value obtained by subtracting a default value β from the currently set lower limit SOCL. The default value β is a value that can suppress over-discharge of the first battery 40. By executing this modification process, the value of the upper limit SOCH becomes larger and the value of the lower limit SOCL becomes smaller compared to before the modification process was executed.

[0025] Then, if the control device 21 has finished processing S120, or if it has made a negative determination in processing S110, it will terminate the execution of this process for the current cycle. <Operation and Effects of This Embodiment> (1) If the full charge capacity CHmax is less than or equal to the threshold CHmaxref, the modification process is executed, which increases the upper limit SOCH and decreases the lower limit SOCL. Therefore, when the degradation level of the first battery 40 is high, the usage range UR is modified to be wider than when the degradation level is low.

[0026] When the operating range UR is widened, the capacity range CHR of the first battery 40 widens during the charging cycle of the first battery 40. Therefore, it is possible to suppress the decrease in the amount of energy EE that can actually be used during the charging cycle of the first battery 40.

[0027] (2) Since the decrease in the amount of power EE that can actually be used during the charging cycle of the first battery 40 can be suppressed, the shortening of the charging cycle period of the first battery 40 can also be suppressed. As a result, the deterioration of the first battery 40 and the deterioration of the circuit that switches between charging and discharging the first battery 40 can also be suppressed.

[0028] (3) By suppressing the shortening of the charging cycle period of the first battery 40, the shortening of the charging cycle period of the second battery 50, which uses the power of the first battery 40, can also be suppressed. As a result, the deterioration of the second battery 50 and the deterioration of the circuit that switches between charging and discharging the second battery 50 can also be suppressed.

[0029] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0030] • A value different from the full charge capacity CHmax may be used to indicate the degree of degradation of the first battery 40. For example, the longer the cumulative usage time of the first battery 40, the more the first battery 40 degrades. Therefore, the cumulative usage time of the first battery 40 may be used as a value indicating the degree of degradation of the first battery 40. Also, the longer the cumulative mileage of the vehicle VC, the more the first battery 40 degrades. Therefore, the cumulative mileage of the vehicle VC may be used as a value indicating the degree of degradation of the first battery 40.

[0031] As shown in Figure 4, as a modification process, a process may be executed to variably set the upper limit SOCH and the lower limit SOCL such that the upper limit SOCH increases and the lower limit SOCL decreases as the full charge capacity CHmax of the first battery 40 decreases. In this case, the decrease in the amount of energy EE that can actually be used in the charging cycle of the first battery 40 can be suppressed more precisely.

[0032] The degradation level of the first battery 40 is classified into classes. The upper limit value SOCH and the lower limit value SOCL may be changed so that the usage range UR widens for classes with a higher degradation level.

[0033] • In the modification process, both the upper limit SOCH and the lower limit SOCL were changed, but it is also acceptable to change only the upper limit SOCH or only the lower limit SOCL. In the above embodiment, the operating range UR was changed based on the degree of degradation of the first battery 40, but the operating range UR may be changed based on other requirements.

[0034] For example, the operating range UR may be changed based on the temperature of the first battery 40. More specifically, if the temperature of the first battery 40 is high, it is conceivable to suppress the input current and output current of the first battery 40 in order to suppress the temperature rise. In this case, when suppressing the input current and output current, it is desirable to increase the voltage of the first battery 40 in order to suppress the decrease in power. Therefore, by increasing the upper limit SOHL of the operating range UR and widening the operating range UR, the voltage of the first battery 40 can be increased, thereby ensuring power while suppressing the temperature rise of the first battery 40.

[0035] Furthermore, for example, when the temperature of the first battery 40 is low, the apparent capacity tends to decrease. Therefore, when the temperature of the first battery 40 is low, by widening the operating range UR compared to when it is high, it becomes possible to suppress the decrease in the amount of energy EE that can actually be used in the charging cycle of the first battery 40.

[0036] Furthermore, the operating range UR may be changed, for example, to suppress the deterioration of the circuit (such as a relay circuit) that switches between charging and discharging the first battery 40, or the circuit (such as a relay circuit) that switches between charging and discharging the second battery 50. In other words, widening the operating range UR suppresses the shortening of the charging cycle period of the first battery 40. Therefore, the increase in the number of times the first battery 40 switches between charging and discharging is suppressed, and thus the deterioration of the circuit that switches between charging and discharging the first battery 40 is suppressed. Also, if the shortening of the charging cycle period of the first battery 40 is suppressed, the shortening of the charging cycle period of the second battery 50, which uses the power of the first battery 40, is also suppressed. Therefore, the increase in the number of times the second battery 50 switches between charging and discharging is suppressed, and thus the deterioration of the circuit that switches between charging and discharging the second battery 50 is suppressed.

[0037] Therefore, the control device 21 estimates the degree of degradation of the switching circuit that switches between charging and discharging the first battery 40 and the second battery 50, based on, for example, the cumulative startup time of the solar charging system 100 and the number of times the switching circuit switches between charging and discharging. When the degree of degradation of the switching circuit is high, the control device 21 may perform a process to change the operating range UR so that the operating range UR is wider than when the degree of degradation is low. In this case, the rate at which the switching circuit deteriorates can be suppressed.

[0038] The first battery 40 was an auxiliary battery that supplied power to the auxiliary equipment of the vehicle VC, but it may also be a battery used for other purposes. The second battery 50 was a drive battery that supplied power to the motor driving the vehicle VC, but it may be a battery used for other purposes.

[0039] Although the battery control device 31 controlled the opening and closing of the relay 60, the control device 21 may directly control the opening and closing of the relay 60. The third converter 70 may be provided within the control unit 20.

[0040] The battery control device 31 may be located within the control unit 20. • The solar charging system 100 was applied to vehicle VCs, but it may also be applied to things other than vehicle VCs.

[0041] The control device 21 is not limited to one that includes a CPU and a memory device and executes software processing. For example, it may include a dedicated hardware circuit, such as an ASIC, that performs hardware processing on at least a portion of what is processed by software in the above embodiment. In other words, the control device may have any of the following configurations (a) to (c): (a) It includes a processing device that executes all of the above processing according to a program and a program storage device such as a ROM that stores the program. (b) It includes a processing device and a program storage device that execute a portion of the above processing according to a program and a dedicated hardware circuit that executes the remaining processing. (c) It includes a dedicated hardware circuit that executes all of the above processing. Here, the software execution device equipped with the processing device and the program storage device, and the dedicated hardware circuit may be one or any number of them. In other words, the above processing can be executed by a processing circuit that includes at least one of one or more software execution devices and one or more dedicated hardware circuits. The program storage device, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0042] 10…Solar panels 20…Control Unit 21...Control device 25…First converter 26…Second converter 30…Battery monitoring unit 30…Battery control unit 31...Battery control unit 40…First Battery 50... Second battery 60… Relay 70...Third converter 100...Solar charging system VC…Vehicle

Claims

1. A solar panel, a first battery for storing the electricity generated by the solar panel, A solar charging system comprising a second battery for storing power supplied from the first battery, and a control device, The first battery is an auxiliary battery that supplies power to the vehicle's auxiliary equipment. The control device performs the following process: when the charge level of the first battery exceeds a predetermined upper limit, it supplies power from the first battery to the second battery to charge the second battery; and when the charge level of the first battery falls below a predetermined lower limit, it stops supplying power from the first battery to the second battery and charges the first battery. When the range from the upper limit to the lower limit is defined as the usable range, The control device is When the degree of degradation of the first battery is high, a modification process is performed to change the usage range so that it becomes wider than when the degree of degradation is low. If the temperature of the first battery is high, the following process is performed: suppressing the output current from the first battery and increasing the upper limit compared to when the temperature is low. Solar charging system.

2. The modification process is a process of changing the usage range such that the usage range becomes wider as the degree of degradation of the first battery increases. The solar charging system according to claim 1.

3. The aforementioned modification process is a process that increases the value of the upper limit and decreases the value of the lower limit compared to before the execution of the modification process. The solar charging system according to claim 1.

4. The second battery is a drive battery that supplies power to the motor that drives the vehicle. The solar charging system according to claim 1.

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