Solar charging system

Abstract

To provide a solar charging system that can reduce loss of electric power.SOLUTION: In a solar charging system 1, generated electric power of a solar panel 10 is supplied to an auxiliary battery 14. A two-way DC / DC converter 18 operates in a first state in which the generated power of the solar panel 10 and the power of the auxiliary battery 14 are supplied to a driving battery 20 of a vehicle, or a second state in which the power of the driving battery 20 is supplied to the auxiliary battery 14. A control unit 34 operates in a first control mode in which it controls the two-way DC / DC converter 18 so that a voltage or a SOC of the auxiliary battery 14 is within a first range, or a second control mode in which it controls the two-way DC / DC converter 18 so that the voltage or the SOC of the auxiliary battery 14 is within a second range wider than the first range. When solar charging is being performed by the solar panel 10, the control unit 34 operates in the second control mode.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] There is a known technique for charging an accessory battery and a driving battery using the generated power of a solar panel mounted on a vehicle. Patent Document 1 discloses a vehicle charging control system that distributes power to the driving battery and the accessory battery at a first distribution ratio when the voltage of the accessory battery is equal to or higher than a predetermined value, and distributes power to the driving battery and the accessory battery at a second distribution ratio in which the ratio of power distributed to the accessory battery is higher than the first distribution ratio when the voltage of the accessory battery is lower than the predetermined value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present inventor has recognized that in a solar charging system for a vehicle, power loss may increase due to repeated charging and discharging between the accessory battery and the driving battery in a situation where sunlight is unstable.

[0005] An object of the present invention is to provide a solar charging system capable of reducing power loss.

Means for Solving the Problems

[0006] To solve the above problems, a solar charging system according to one aspect of the present invention comprises a solar panel, an auxiliary battery supplied with power generated by the solar panel, a vehicle drive battery, a DC / DC converter operating in a first state that supplies power generated by the solar panel and power from the auxiliary battery to the drive battery, or in a second state that supplies power from the drive battery to the auxiliary battery, and a control unit that controls the DC / DC converter. The control unit controls the auxiliary battery S A first control mode that controls the DC / DC converter so that the OC is within a first range, or the auxiliary battery S The DC / DC converter operates in a second control mode that controls the DC / DC converter so that the OC is within a second range wider than the first range, and operates in the second control mode when solar charging is performed by the solar panel. When solar charging is in progress, the control unit controls the DC / DC converter to the second state or the stopped state to charge the auxiliary battery when the SOC of the auxiliary battery reaches the lower limit of the second range, and controls the DC / DC converter to the first state to charge the drive battery with the power generated by the solar panel and the power of the auxiliary battery when the SOC of the auxiliary battery reaches the upper limit of the second range. [Effects of the Invention]

[0007] According to the present invention, a solar charging system that can reduce power loss can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram schematically shows the configuration of the solar charging system according to the embodiment. [Figure 2] Figure 1 shows an example of the first and second ranges of the State of Charge (SOC) of the auxiliary battery. [Figure 3] Figures 3(a) to 3(c) illustrate the charging operation of the auxiliary battery in the second control mode. [Figure 4] Figures 4(a) and 4(b) illustrate the pumping operation in the second control mode. [Figure 5] Figures 5(a) and 5(b) illustrate the operation of the first control mode. [Figure 6] This flowchart shows the control process for a solar charging system. [Modes for carrying out the invention]

[0009] Figure 1 schematically shows the configuration of the solar charging system 1 according to the embodiment. The solar charging system 1 is mounted on an electric vehicle (not shown). The electric vehicle is, for example, an electric vehicle (BEV: Battery Electric Vehicle), a hybrid vehicle (HEV: Hybrid Electric Vehicle), a plug-in hybrid vehicle (PHEV: Plug-in Hybrid Electric Vehicle), or a fuel cell vehicle (FCEV: Fuel Cell Electric Vehicle) that uses an electric motor as a power source. The electric vehicle may be a vehicle driven by a driver or an autonomous vehicle.

[0010] The solar charging system 1 comprises a solar panel 10, a DC / DC converter 12, an auxiliary battery 14, an auxiliary device 16, a bidirectional DC / DC converter 18, a drive battery 20, and a control device 30.

[0011] The solar panel 10 is a solar cell module, which is an assembly of solar cells that generate electricity based on sunlight. The power generated by the solar panel 10 depends on the intensity of sunlight. The solar panel 10 is connected to the input terminal of the DC / DC converter 12. The power generated by the solar panel 10 is output to the DC / DC converter 12. The solar panel 10 is installed, for example, on the roof of a vehicle.

[0012] The output terminals of the DC / DC converter 12 are connected to the auxiliary battery 14, the auxiliary 16, and the bidirectional DC / DC converter 18. The DC / DC converter 12 can convert the power generated by the solar panel 10 into power and supply it to the auxiliary battery 14, the auxiliary 16, and the bidirectional DC / DC converter 18. The DC / DC converter 12 steps down or steps up the output voltage of the solar panel 10 to a predetermined voltage according to the control of the control device 30, and outputs the stepped-down or stepped-up voltage to the auxiliary battery 14, etc. The DC / DC converter 12 performs MPPT (Maximum Power Point Tracking) control to maximize the output power of the solar panel 10.

[0013] The auxiliary battery 14 is a rechargeable secondary battery, such as a lithium-ion battery. The auxiliary battery 14 is a low-voltage battery with a lower voltage than the drive battery 20. The auxiliary battery 14 can be charged by the power generated by the solar panel 10. The auxiliary battery 14 may also be charged by the power of the drive battery 20. The auxiliary battery 14 can supply power to the auxiliary 16. The auxiliary battery 14 may also charge the drive battery 20.

[0014] Auxiliary equipment 16 is a load such as electronic equipment installed in the vehicle. Auxiliary equipment 16 may include, for example, headlights, navigation systems, audio systems, air conditioners, autonomous driving systems, advanced driver assistance systems, etc. Auxiliary equipment 16 operates using power supplied from the auxiliary battery 14.

[0015] The bidirectional DC / DC converter 18 has a first terminal and a second terminal. The first terminal is connected to the output terminal of the DC / DC converter 12 and the auxiliary battery 14. The second terminal is connected to the drive battery 20. The bidirectional DC / DC converter 18 operates in a first state, where it boosts the voltage at the first terminal and outputs the boosted voltage from the second terminal, or in a second state, where it lowers the voltage at the second terminal and outputs the lowered voltage from the first terminal, according to the control of the control device 30.

[0016] The drive battery 20 is a rechargeable secondary battery such as a lithium-ion battery, for example. The drive battery 20 can also be called a high-voltage battery. The drive battery 20 can supply electric power to an electric motor that generates the driving force of the vehicle via an inverter (not shown). The drive battery 20 can be charged with electric power supplied from a charging stand outside the vehicle via an in-vehicle charging device (not shown).

[0017] The control device 30 controls the DC / DC converter 12 and the bidirectional DC / DC converter 18 based on the output voltage of the solar panel 10, the voltage and current of the auxiliary battery 14, and the voltage of the drive battery 20 detected by a voltage sensor and a current sensor (not shown). The control device 30 includes a SOC estimation unit 32 and a control unit 34.

[0018] The configuration of the control device 30 can be realized hardware-wise by the CPU, memory, and other LSIs of an arbitrary computer, and software-wise by a program loaded into the memory, etc. Here, functional blocks realized by their cooperation are depicted. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by only hardware, only software, or combinations thereof.

[0019] The SOC estimation unit 32 sequentially estimates the estimated value of the SOC of the auxiliary battery 14 based on the voltage and current of the auxiliary battery 14, and sequentially supplies the estimated value of the SOC to the control unit 34.

[0020] The control unit 34 controls the charge and discharge of the auxiliary battery 14 by controlling the bidirectional DC / DC converter 18 based on the received estimated value of the SOC, the output voltage of the solar panel 10, the voltage and current of the auxiliary battery 14, and the voltage of the drive battery 20. Hereinafter, the estimated value of the SOC will be simply referred to as SOC.

[0021] The control unit 34 operates in either a first control mode or a second control mode. The control unit 34 operates in the first control mode when the solar panel 10 is not charging and the bidirectional DC / DC converter 18 is not operating in the first state. The control unit 34 operates in the second control mode when the solar panel 10 is charging or the bidirectional DC / DC converter 18 is operating in the first state. Solar charging is equivalent to the solar panel 10 generating electricity.

[0022] In the first control mode, the control unit 34 controls the bidirectional DC / DC converter 18 to a second state or a stopped state so that the SOC of the auxiliary battery 14 falls within a first range. In the second control mode, the control unit 34 controls the bidirectional DC / DC converter 18 to a first state, a second state, or a stopped state so that the SOC of the auxiliary battery 14 falls within a second range, which is wider than the first range.

[0023] The control unit 34 may control the bidirectional DC / DC converter 18 so that the voltage of the auxiliary battery 14 falls within a first or second range. Alternatively, the control unit 34 may control the bidirectional DC / DC converter 18 so that the voltage of the auxiliary battery 14 falls within a first or second voltage range, and the State of Charge (SOC) falls within a first or second SOC range.

[0024] Figure 2 shows an example of the first range R1 and second range R2 of the State of Charge (SOC) of the auxiliary battery 14 in Figure 1. The upper limit S2H of the second range R2 is greater than the upper limit S1H of the first range R1. The lower limit S2L ​​of the second range R2 is less than the lower limit S1L of the first range R1.

[0025] The upper limit S2H of the second range R2 may be greater than the upper limit S1H of the first range R1, and the lower limit S2L ​​of the second range R2 may be equal to the lower limit S1L of the first range R1. Alternatively, the upper limit S2H of the second range R2 may be equal to the upper limit S1H of the first range R1, and the lower limit S2L ​​of the second range R2 may be less than the lower limit S1L of the first range R1.

[0026] Next, the charging and discharging operation of the solar charging system 1 will be explained with reference to Figures 3-5. The control device 30 is not shown in Figures 3-5.

[0027] (Second control mode) Figures 3(a) to 3(c) illustrate the charging operation of the auxiliary battery 14 in the second control mode. As previously described, in the second control mode, the State of Charge (SOC) of the auxiliary battery 14 is controlled within the second range.

[0028] Figure 3(a) shows a state where solar radiation is relatively high and the power generated by the solar panel 10 is relatively large. The bidirectional DC / DC converter 18 is controlled to a stopped state. In the state shown in Figure 3(a), the power generated by the solar panel 10 is assumed to be greater than the power consumed by the auxiliary equipment 16. Therefore, the auxiliary battery 14 is charged with the generated power, and the State of Charge (SOC) of the auxiliary battery 14 increases. Since the auxiliary battery 14 can be charged using solar energy, it is highly convenient. In Figures 3-5, the arrows indicate the power supply path, and the thickness of the arrows roughly indicates the magnitude of the power.

[0029] When the situation changes from one with relatively high solar radiation to one with relatively low solar radiation, the state shown in Figure 3(b) is reached.

[0030] Figure 3(b) shows a state where solar radiation is relatively low and the power generated by the solar panel 10 is relatively small. The bidirectional DC / DC converter 18 is controlled to a stopped state. In the state shown in Figure 3(b), the power generated by the solar panel 10 is assumed to be less than the power consumed by the auxiliary equipment 16. Therefore, the state of charge (SOC) of the auxiliary battery 14 decreases due to the power consumption of the auxiliary equipment 16. When solar radiation recovers, the state returns to that shown in Figure 3(a).

[0031] If solar radiation does not recover and the SOC of the auxiliary battery 14 reaches the lower limit of the second range, the operation transitions to that shown in Figure 3(c). In other words, when solar charging is in progress, if the SOC of the auxiliary battery 14 reaches the lower limit of the second range, the control unit 34 controls the bidirectional DC / DC converter 18 to the second state in order to charge the auxiliary battery 14. Specifically, when solar charging is in progress and the bidirectional DC / DC converter 18 is stopped, if the SOC of the auxiliary battery 14 reaches the lower limit of the second range, the control unit 34 controls the bidirectional DC / DC converter 18 to the second state.

[0032] Figure 3(c) follows Figure 3(b), showing a state where solar radiation is relatively low, the power generated by the solar panel 10 is relatively low, and the auxiliary battery 14 is being charged using power from the drive battery 20 as well. In the state shown in Figure 3(c), the bidirectional DC / DC converter 18 operates in a second state, supplying power from the drive battery 20 to the auxiliary battery 14. As a result, the auxiliary battery 14 is charged with power from the drive battery 20 and the power generated by the solar panel 10, increasing the State of Charge (SOC) of the auxiliary battery 14. Therefore, the SOC of the auxiliary battery 14 can be increased even when solar radiation is insufficient.

[0033] When the State of Charge (SOC) of the auxiliary battery 14 reaches the upper limit of the second range due to charging, the pumping operation shown in Figure 4(a) is initiated.

[0034] On the other hand, if the conditions in Figure 3(a) continue to be relatively high in terms of solar radiation, and the State of Charge (SOC) of the auxiliary battery 14 reaches the upper limit of the second range due to charging by the power generated by the solar panel 10, the system will transition to the pumping operation shown in Figure 4(a).

[0035] Specifically, when solar charging is in progress, the control unit 34 controls the bidirectional DC / DC converter 18 to a first state so that the drive battery 20 is charged with the power generated by the solar panel 10 and the power from the auxiliary battery 14 when the State of Charge (SOC) of the auxiliary battery 14 reaches the upper limit of the second range.

[0036] Figures 4(a) and 4(b) illustrate the pumping operation in the second control mode. Figure 4(a) shows a state where there is sunlight and the solar panel 10 is generating power. In the state shown in Figure 4(a), the bidirectional DC / DC converter 18 operates in a first state, supplying power generated by the solar panel 10 and power from the auxiliary battery 14 to the drive battery 20. As a result, the drive battery 20 is charged with power from the auxiliary battery 14 and power generated by the solar panel 10. This operation is called the pumping operation. The state of charge (SOC) of the drive battery 20 increases, and the state of charge (SOC) of the auxiliary battery 14 decreases. Since the drive battery 20 can be charged with power generated by solar energy and power from the auxiliary battery 14 including said power, it is convenient and economical.

[0037] When the state of charge (SOC) of the auxiliary battery 14 reaches the lower limit of the second range in the state shown in Figure 4(a), the system transitions to the operation shown in Figures 3(a) and 3(b) described above. In other words, when solar charging is in progress, if the state of charge of the auxiliary battery 14 reaches the lower limit of the second range, the control unit 34 controls the bidirectional DC / DC converter 18 to a stopped state so that the auxiliary battery 14 is charged with the power generated by the solar panel 10. Specifically, when solar charging is in progress and the bidirectional DC / DC converter 18 is operating in the first state, if the state of charge of the auxiliary battery 14 reaches the lower limit of the second range, the control unit 34 controls the bidirectional DC / DC converter 18 to a stopped state. This allows the auxiliary battery 14 to be charged again using the power generated by the solar panel 10. If there is sufficient sunlight, the state shown in Figure 3(a) and Figure 4(a) can be repeated alternately, allowing the drive battery 20 to be repeatedly charged with power generated by solar energy.

[0038] Figure 4(b) shows the state in Figure 4(a) where there is no sunlight and the solar panel 10 has stopped generating power. In the second control mode, if the bidirectional DC / DC converter 18 is operating in the first state, i.e., in the pumping operation, the control unit 34 continues the second control mode even after solar charging is complete. Therefore, the bidirectional DC / DC converter 18, which continues to operate in the first state, continues to supply power from the auxiliary battery 14 to the drive battery 20. Thus, the SOC of the auxiliary battery 14 decreases. If the control unit 34 continues the second control mode even after solar charging is complete, and the SOC of the auxiliary battery 14 reaches the lower limit of the second range while the solar panel 10 is not generating power, it switches to the first control mode.

[0039] This control allows the pumping operation to continue even if solar charging ends during the pumping operation, and to supply power from the auxiliary battery 14, which includes power generated by the solar panel 10, to the drive battery 20 until it reaches the lower limit of the second range.

[0040] Furthermore, if the solar panel 10 runs out of power during the charging operation of the auxiliary battery 14 shown in Figures 3(a) to (c), solar charging will also end at that point. In the second control mode, if the bidirectional DC / DC converter 18 is not operating in the first state, i.e., not in pumping operation, the control unit 34 will switch to the first control mode when solar charging ends.

[0041] During solar charging, the system is controlled within a second range, which is wider than the first range. Therefore, when solar charging ends and the second control mode ends, the auxiliary battery 14 may be in a relatively low state of depletion or low charge, or it may be in a relatively high state of charge. If left in these states for an extended period, the auxiliary battery 14 may deteriorate.

[0042] Therefore, when the second control mode ends, the control unit 34 controls the bidirectional DC / DC converter 18 to adjust the voltage of the auxiliary battery 14 if the voltage of the auxiliary battery 14 is higher than a predetermined first voltage or lower than a predetermined second voltage. The second voltage is lower than the first voltage.

[0043] The first voltage may be a value corresponding to the upper limit of the first range, or it may be greater than the value corresponding to the upper limit of the first range and less than the value corresponding to the upper limit of the second range.

[0044] The second voltage may be a value corresponding to the lower limit of the first range, or it may be smaller than the value corresponding to the lower limit of the first range and larger than the value corresponding to the lower limit of the second range.

[0045] The value corresponding to the upper limit of the first range represents the voltage of the auxiliary battery 14 when the SOC is at the upper limit of the first range. The same applies to the value corresponding to the lower limit of the first range, etc. Note that if the first and second ranges are voltage ranges, the value corresponding to the upper limit of the first range represents the upper limit of the first range. The same applies to the value corresponding to the lower limit of the first range, etc.

[0046] Specifically, when solar charging is complete, if the voltage of the auxiliary battery 14 is higher than the first voltage, the control unit 34 controls the bidirectional DC / DC converter 18 to the first state until the voltage of the auxiliary battery 14 drops to a predetermined third voltage. As a result, power from the auxiliary battery 14 is supplied to the drive battery 20, and the voltage of the auxiliary battery 14 drops. The third voltage is lower than the first voltage and higher than the lower limit of the first range.

[0047] When solar charging is complete, if the voltage of the auxiliary battery 14 is lower than the second voltage, the control unit 34 controls the bidirectional DC / DC converter 18 to the second state until the voltage of the auxiliary battery 14 rises to a predetermined fourth voltage. As a result, power from the drive battery 20 is supplied to the auxiliary battery 14, and the voltage of the auxiliary battery 14 rises. The fourth voltage is higher than the second voltage and lower than the upper limit of the first range. The first, second, third, and fourth voltages can be determined as appropriate by experiment or simulation.

[0048] This prevents the auxiliary battery 14 from remaining in a depleted, low-charge, or high-charge state. Therefore, the deterioration of the auxiliary battery 14 can be suppressed.

[0049] (First control mode) Figures 5(a) and 5(b) illustrate the operation of the first control mode. As previously described, in the first control mode, the SOC of the auxiliary battery 14 is controlled within a first range.

[0050] Figure 5(a) shows the state in which the bidirectional DC / DC converter 18 is stopped. In the state shown in Figure 5(a), the solar panel 10 is not generating power, so the state of charge (SOC) of the auxiliary battery 14 decreases due to the power consumption of the auxiliary equipment 16.

[0051] When the SOC of the auxiliary battery 14 reaches the lower limit of the first range, the operation transitions to that shown in Figure 5(b). Specifically, in the first control mode, when the SOC of the auxiliary battery 14 reaches the lower limit of the first range, the control unit 34 controls the bidirectional DC / DC converter 18 to the second state.

[0052] Figure 5(b) shows the state in which the auxiliary battery 14 is being charged. In the state shown in Figure 5(b), the bidirectional DC / DC converter 18 operates in a second state, supplying power from the drive battery 20 to the auxiliary battery 14. As a result, the auxiliary battery 14 is charged with power from the drive battery 20, and the state of charge (SOC) of the auxiliary battery 14 increases.

[0053] When the State of Charge (SOC) of the auxiliary battery 14 reaches the upper limit of the first range due to charging, the operation returns to that shown in Figure 5(a). Specifically, in the first control mode, when the SOC of the auxiliary battery 14 reaches the upper limit of the first range, the control unit 34 controls the bidirectional DC / DC converter 18 to a stopped state.

[0054] In the first control mode, solar charging begins when the solar panel 10 starts generating power. When solar charging begins in the first control mode, the control unit 34 switches to the second control mode.

[0055] Here, the inventors describe a comparative example they recognize. The comparative example's solar charging system has the same configuration as the solar charging system 1 of the embodiment, but the control is different. In the comparative example, a common first control range is used in both the first control mode and the second control mode. In other words, even in the second control mode, charging and discharging are controlled within a first range that is narrower than the second range of the embodiment.

[0056] In the comparative example, as in Figure 3(b), when solar radiation decreases and the power generated by the solar panel decreases in the second control mode, the SOC of the auxiliary battery may decrease due to power consumption by the auxiliary equipment. In the comparative example, compared to the embodiment, the upper limit of the control range is lower and the lower limit is higher in the second control mode, so the SOC of the auxiliary battery can decrease to the lower limit in a shorter time. When the SOC of the auxiliary battery decreases to the lower limit, the auxiliary battery is charged with the power generated and the power of the drive battery, as in Figure 3(c). In other words, in situations where solar radiation is unstable, when there is a lot of solar radiation, the power that has been boosted by a pumping operation as in Figure 4(a) and stored in the drive battery from the auxiliary battery can be used again to charge the auxiliary battery by stepping down when there is little solar radiation. At this time, losses occur in the bidirectional DC / DC converter in both the boost operation and the step-down operation.

[0057] The inventors of the present invention recognized that, in comparative examples, under conditions of unstable solar radiation, power loss increases due to the relatively frequent exchange of power between such auxiliary batteries and drive batteries.

[0058] In contrast to this comparative example, in this embodiment, the State of Charge (SOC) of the auxiliary battery 14 is controlled within a second range, which is wider than the first range, during solar charging. Therefore, in situations where solar radiation is unstable, the frequency of charging and discharging of the auxiliary battery 14 during solar charging can be reduced compared to the comparative example. In other words, the frequency of power exchange between the auxiliary battery 14 and the drive battery 20 can be reduced compared to the comparative example. Thus, power loss caused by repeated charging and discharging can be reduced.

[0059] Specifically, because the upper limit of the second range is higher than that of the first range, the SOC of the auxiliary battery 14 can be made higher than in the comparative example during solar charging as shown in Figure 3(a). As a result, the amount of power available to the auxiliary 16 increases. Therefore, even when solar radiation decreases and the situation is as shown in Figure 3(b), there is a time leeway before the SOC of the auxiliary battery 14 decreases and reaches the lower limit of the second range. Also, because the lower limit of the second range is lower than that of the first range, even in the state of reduced solar radiation shown in Figure 3(b), there is a time leeway before the SOC of the auxiliary battery 14 decreases and reaches the lower limit of the second range.

[0060] From the above, the SOC of the auxiliary battery 14 is less likely to reach the lower limit of the second range than in the comparative example. Therefore, the operation of charging the auxiliary battery 14 with the power of the drive battery 20 shown in Figure 3(c) is less likely to occur. If sunlight recovers during the state shown in Figure 3(b), the SOC of the auxiliary battery 14 can be increased again with the power generated by the solar panel 10, so the operation shown in Figure 3(c) may not occur.

[0061] Furthermore, when not charging via solar power, the State of Charge (SOC) of the auxiliary battery 14 is controlled within a relatively narrow first range, thus reducing the likelihood of the auxiliary battery 14 degrading.

[0062] Next, the overall operation of the solar charging system 1 with the above configuration will be explained. Figure 6 is a flowchart showing the control process of the solar charging system 1. The process in Figure 6 is executed repeatedly.

[0063] If the second control mode is not started (N in S10), the control unit 34 operates in the first control mode, controls the SOC of the auxiliary battery 14 within the first range (S20), and terminates the process.

[0064] If the second control mode is started (Y in S10), the control unit 34 operates in the second control mode and controls the state of charge (SOC) of the auxiliary battery 14 within the second range (S12). If the second control mode is not terminated (N in S14), the process returns to S12.

[0065] When the second control mode is terminated (Y in S14), if the voltage of the auxiliary battery 14 is higher than the first voltage or lower than the second voltage (Y in S16), the control unit 34 controls the bidirectional DC / DC converter 18 to adjust the voltage of the auxiliary battery 14 (S18), and the process moves to S20. If the conditions of S16 are not met (N in S16), the process moves to S20.

[0066] The present invention has been described above based on embodiments. The embodiments are merely illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of each component and each processing process, and that such modifications also fall within the scope of the present invention. [Explanation of Symbols]

[0067] 1...Solar charging system, 10...Solar panel, 12...DC / DC converter, 14...Auxiliary battery, 16...Auxiliary equipment, 18...Bidirectional DC / DC converter, 20...Drive battery, 30...Control device, 32...SOC estimation unit, 34...Control unit.

Claims

1. Solar panels and An auxiliary battery supplied with power generated by the aforementioned solar panel, The vehicle's drive battery, A DC / DC converter that operates in a first state, supplying power generated by the solar panel and power from the auxiliary battery to the drive battery, or in a second state, supplying power from the drive battery to the auxiliary battery, A control unit that controls the DC / DC converter, Equipped with, The control unit, The DC / DC converter operates in a first control mode that controls the DC / DC converter so that the SOC of the auxiliary battery is within a first range, or in a second control mode that controls the DC / DC converter so that the SOC of the auxiliary battery is within a second range wider than the first range. When charging using the aforementioned solar panel, the system operates in the second control mode. The control unit, when solar charging is in progress, When the State of Charge (SOC) of the auxiliary battery reaches the lower limit of the second range, the DC / DC converter is controlled to the second state or the stopped state to charge the auxiliary battery. When the State of Charge (SOC) of the auxiliary battery reaches the upper limit of the second range, the DC / DC converter is controlled to the first state so as to charge the drive battery with the power generated by the solar panel and the power of the auxiliary battery. A solar charging system characterized by the following features.

2. The control unit, When solar charging is in progress and the DC / DC converter is stopped, if the SOC of the auxiliary battery reaches the lower limit of the second range, the DC / DC converter is controlled to the second state. When solar charging is in progress and the DC / DC converter is operating in the first state, if the SOC of the auxiliary battery reaches the lower limit of the second range, the DC / DC converter is controlled to a stopped state. In the first control mode, when the SOC of the auxiliary battery reaches the lower limit of the first range, the DC / DC converter is controlled to the second state, and when the SOC of the auxiliary battery reaches the upper limit of the first range, the DC / DC converter is controlled to the stopped state. The solar charging system according to claim 1.

3. When the second control mode ends, the control unit If the voltage of the auxiliary battery is higher than a predetermined first voltage, the DC / DC converter is controlled to the first state. If the voltage of the auxiliary battery is lower than a predetermined second voltage which is lower than the first voltage, the DC / DC converter is controlled to the second state. A solar charging system according to claim 1 or 2, characterized by the features described above.

4. The control unit, If the DC / DC converter is not operating in the first state in the second control mode, when solar charging is complete, the system switches to the first control mode. In the second control mode, if the DC / DC converter is operating in the first state, the second control mode continues even after solar charging is completed, and when the SOC of the auxiliary battery reaches the lower limit of the second range, the system switches to the first control mode. A solar charging system according to claim 1 or 2, characterized by the features described above.

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