Method of testing at least one photovoltaic cell of a solar charge arrangement for a vehicle

Abstract

The invention relates to a method of testing at least one photovoltaic cell (2) of a solar charge arrangement (4) for a vehicle (1) using a test arrangement (5), wherein the test arrangement (5) comprises an optical sensor (6), in particular a camera (7), wherein a reverse current (11) is applied to the at least one photovoltaic cell (2), wherein the photovoltaic cell (2) in response to the reverse current (11) emits light, wherein the optical sensor (6) generates sensor data (14) by capturing the emitted light, in particular makes an image of the at least one photovoltaic cell (2), wherein the test arrangement (5) comprises a control unit (15) for outputting and / or analyzing the sensor data (14), wherein the solar charge arrangement (4) comprises a solar charge controller (16), wherein the at least one photovoltaic cell (2) is controlled by the solar charge controller (16), wherein the solar charge controller (16) controls the photovoltaic cell (2) while the photovoltaic cell (2) generates energy from sunlight, wherein the solar charge controller (16) applies the reverse current (11) to the at least one photovoltaic cell (2).

Description

[0001] Method of testing at least one photovoltaic cell of a solar charge arrangement for a vehicle

[0002] The present invention relates to a method of testing at least one photovoltaic cell of a solar charge arrangement for a vehicle according to claim 1 , to a solar charge controller according to the general part of claim 12, to a solar charge arrangement according to claim 13, to a vehicle according to claim 14 and to a test arrangement according to claim 15.

[0003] The present focus lies on self-charging electric vehicles equipped with photovoltaic cells. These vehicles are able to obtain at least a part of the power needed via the photovoltaic cells instead of either external charging, if the vehicle is an electric vehicle, or internal charging of a battery via a combustion engine. By using photovoltaic cells, the need for fuel or charging of heavy vehicles like buses, trucks but also boats and airplanes, can be reduced. Photovoltaic cells can also help reduce the environmental impact of the vehicle by using a clean, renewable energy source.

[0004] With a recent upsurge of vehicles equipped with photovoltaic cells, improvements of the manufacturing process including testing and regular maintenance of photovoltaic cells are needed. Photovoltaic cells for vehicles have different requirements regarding quality and speed of production than stationary photovoltaic cells. Further, they are subjected to harsher environmental conditions, e.g. vibrations, than stationary photovoltaic cells. It is known that the functional state of photovoltaic cells can be checked by using the effect of electroluminescence of the photovoltaic cells. By applying a voltage to the photovoltaic cells, a reverse current flows through the photovoltaic cells, causing the photovoltaic cells to emit light. This light, depending on the material of the photovoltaic cell, may be in the visual or infrared spectrum.

[0005] The emitted light can be captured by an optical sensor like a camera and evaluated by an expert or automatically. It is possible to recognize several different defects of the photovoltaic cells with this method. Electroluminescence imaging of photovoltaic cells is conventionally done by connecting an external power supply unit to the photovoltaic cells. Connecting an external power supply unit is not an efficient process and specifically problematic if the photovoltaic cells are mounted to, in particular integrated into, a vehicle.

[0006] It is an object to improve on the efficiency of testing and / or production of vehicle mounted photovoltaic cells.

[0007] The above-noted object is solved by the features of claim 1 .

[0008] The main realization of the present invention is that vehicle mounted photovoltaic cells may be part of a solar charge arrangement which comprises a solar charge controller able to generate the reverse current necessary for electroluminescence. It is therefore possible to use this solar charge controller to apply the reverse current. An external power supply unit is therefore not needed.

[0009] Proposed is a method of testing at least one photovoltaic cell of a solar charge arrangement for a vehicle using a test arrangement, wherein the test arrangement comprises an optical sensor, in particular a camera, wherein a reverse current is applied to the at least one photovoltaic cell, wherein the photovoltaic cell in response to the reverse current emits light, wherein the optical sensor generates sensor data by capturing the emitted light, in particular makes an image of the at least one photovoltaic cell, wherein the test arrangement comprises a control unit for outputting and / or analyzing the sensor data, wherein the solar charge arrangement comprises a solar charge controller, wherein the at least one photovoltaic cell is controlled by the solar charge controller, wherein the solar charge controller controls the photovoltaic cell while the photovoltaic cell generates energy from sunlight, wherein the solar charge controller applies the reverse current to the at least one photovoltaic cell.

[0010] According to one embodiment it is proposed that the solar charge controller comprises a bidirectional DC-DC converter and / or is an MPPT solar charge controller, preferably, that the solar charge controller comprises a first stage bidirectional DC-DC converter providing MPPT functionality and connected to the at least one photovoltaic cell, that the solar charge controller comprises an LV second stage bidirectional DC-DC converter for converting an output of the first stage bidirectional DC-DC converter into 12 V or 24 V or 48 V as the voltage of a board net of the vehicle, and / or, that the solar charge controller comprises an HV second stage bidirectional DC-DC converter for converting an output of the first stage bidirectional DC-DC converter into a high voltage of an electric vehicle.

[0011] If the solar charge controller comprises a bidirectional DC / DC converter this DC / DC converter can be used to direct the current of the photovoltaic cells during energy generation of the photovoltaic cells and can also be used for electroluminescence. The energy for generating the reverse current may come directly from the vehicle. In this embodiment, no external battery is needed. However, if the photovoltaic cells are tested before being mounted to a vehicle, an external battery may be used.

[0012] According to one embodiment it is proposed that a battery, in particular a vehicle battery, is connected to the solar charge arrangement and provides the energy for the reverse current, that a DC-DC converter of the solar charge arrangement, in particular the bidirectional DC-DC-converter, converts a voltage from the battery into a different voltage.

[0013] According to one embodiment it is proposed that a vehicle battery is connected to the LV second stage bidirectional DC-DC converter or the HV second stage bidirectional DC-DC converter and provides the energy for the reverse current, preferably, that the LV second stage bidirectional DC-DC converter or the HV second stage bidirectional DC-DC converter provides energy to the first stage bidirectional DC-DC converter which generates the reverse current.

[0014] According to one embodiment it is proposed that the solar charge arrangement comprises several strings, each string comprising at least one, preferably several, photovoltaic cells, that the solar charge arrangement comprises multiple, in particular bidirectional, first stage DC-DC converters, in particular providing MPPT functionality, that each first stage DC-DC converter controls at least one, preferably exactly one, string, preferably, that the energy provided by the battery is provided to more than one first stage bidirectional DC-DC converter at once or successively. According to one embodiment it is proposed that the solar charge arrangement comprises a vehicle communication interface, in particular CAN interface, adapted to communicate in at least one direction, preferably bidirectionally, with a vehicle, preferably, that the solar charge controller is adapted to perform a function for charging a battery of a vehicle by interacting with vehicle electronics, e.g. reading a signal from vehicle electronics or sending a signal to vehicle electronics.

[0015] According to one embodiment it is proposed that the solar charge controller comprises a telemetry interface adapted to communicate with a control unit external to the vehicle, preferably, that the control unit is part of the test arrangement, and / or, that the control unit sends a test command to the solar charge arrangement and the solar charge arrangement generates the reverse current in response to the test command.

[0016] By providing a telemetry interface, the solar charge controller may perform several functions during maintenance or normal use. For example, the solar charge controller may send functional and statistical data to a control unit during maintenance or regularly for example over a wireless connection. Enabling the solar charge controller to receive an external test command makes it possible to start the electroluminescence imaging when wanted without needing the vehicle to provide this functionality. It also makes it possible to test the solar charge arrangement when it is not connected to a vehicle in an easy manner.

[0017] According to one embodiment it is proposed that the photovoltaic cell is embedded in a vehicle part, in particular vehicle body part or retrofit vehicle part, preferably, that the vehicle part has been produced by overmolding the at least one photovoltaic cell.

[0018] According to one embodiment it is proposed that the test arrangement comprises a dark chamber, that the photovoltaic cell is placed in the dark chamber, that the sensor data is generated while the photovoltaic cell is in the dark chamber, and / or, that the testing is performed as an end of line test, in particular before the solar charge arrangement is mounted to the vehicle, and / or as a maintenance test after the solar charge arrangement has been mounted to the vehicle, preferably, that the testing is repeated as part of a regular maintenance.

[0019] End of line testing the photovoltaic cell is a good way of ensuring that no faulty photovoltaic cells are mounted to a vehicle. Testing during regular maintenance allows detecting faults early and before they are detectable by the solar charge controller alone. It is therefore possible to exchange the photovoltaic cells if they are not working properly and increase the overall produced energy. It also becomes possible to learn more about the life cycle of the photovoltaic cells and improve further generations.

[0020] According to one embodiment it is proposed that a processing unit, in particular a microcontroller, of the solar charge arrangement provides one or more functionalities of enabling communication with the vehicle, in particular so that the vehicle allows power to be drawn from the vehicle battery, control power drawn from the vehicle battery, control step down from high voltage to intermediate voltage via the HV second stage bidirectional DC-DC converter, control step up or step down from intermediate voltage to the photovoltaic cell via the first stage bidirectional DC-DC converter, control step up or step down from low voltage to intermediate voltage via the LV second stage bidirectional DC-DC converter, increase voltage and current output to the photovoltaic cell until a pre-defined voltage and / or current is achieved at the photovoltaic cell for electroluminescence, ensure that the reverse current stays below a maximum current of the photovoltaic cell.

[0021] According to one embodiment it is proposed that the solar charge controller applies the reverse current as a defined current and measures the voltage applied or applies a defined voltage and measures the current applied, that the solar charge arrangement compares the measured current or voltage with a specified voltage or current to identify a fault of the photovoltaic cell. The solar charge controller may compare measurements made during application of the reverse current with standard values. Defective photovoltaic cells may draw more or less current than healthy photovoltaic cells thereby giving a further data point to identify faulty photovoltaic cells.

[0022] Another teaching which is of equal importance relates to a solar charge controller adapted to control at least one photovoltaic cell, wherein the solar charge controller controls the photovoltaic cell while the photovoltaic cell generates energy from sunlight.

[0023] Essential according to this further teaching is that the solar charge controller applies a reverse current to the at least one photovoltaic cell such that the photovoltaic cell in response to the reverse current emits light.

[0024] All explanations given with regard to the proposed method are fully applicable.

[0025] Another teaching which is of equal importance relates to a solar charge arrangement comprising at least one photovoltaic cell and a proposed solar charge controller.

[0026] All explanations given with regard to the proposed method and the proposed solar charge controller are fully applicable.

[0027] Another teaching which is of equal importance relates to a vehicle comprising a proposed solar charge arrangement.

[0028] All explanations given with regard to the proposed method, the proposed solar charge controller and the proposed solar charge arrangement are fully applicable.

[0029] Another teaching which is of equal importance relates to a test arrangement adapted to communicate with a proposed solar charge controller, wherein the test arrangement comprises an optical sensor, in particular a camera, wherein the optical sensor generates sensor data by capturing emitted light, in particular makes an image of the at least one photovoltaic cell, wherein the test arrangement comprises a control unit for outputting and / or analyzing the sensor data.

[0030] All explanations given with regard to the proposed method, the proposed solar charge controller, the proposed solar charge arrangement and the proposed vehicle are fully applicable.

[0031] In the following, embodiments of the invention are explained with respect to the drawing. The drawing shows in

[0032] Fig. 1 , in a) two vehicles with photovoltaic cells and b) a test arrangement,

[0033] Fig. 2, in a) a string of photovoltaic cells, in b) an equivalent circuit diagram of a photovoltaic cell during energy generation from sunlight and in c) while applying a reverse current,

[0034] Fig. 3, a solar charge controller and its connections to a vehicle battery, the photovoltaic cells and for communication with the vehicle,

[0035] Fig. 4, several first stage DC-DC controllers controlled by one microcontroller and schematically charging a battery and

[0036] Fig. 5, an overall view of a retrofit solar charge arrangement for combustion engine vehicles.

[0037] The present focus lies on a vehicle 1 with photovoltaic cells 2. Fig. 1 shows two vehicles 1 with photovoltaic cells 2 arranged on the body of the vehicle 1 as preferred vehicles 1 . The vehicle 1 may be an electric vehicle 1 or a vehicle 1 with a combustion engine. The vehicle 1 may be a bus, a truck, a boat, an airplane or any other vehicle 1 which profits from generating some electric energy via photovoltaic cells 2. Especially buses and trucks need a relevant amount of electrical energy, conventionally generated via the combustion engine and a generator.

[0038] The photovoltaic cells 2 may be integrated into the body of the vehicle 1 or secured, for example glued, on the body of the vehicle 1. Fig. 1 shows a bus and a truck. An electric vehicle 1 is propelled by an electric drive. Preferably, the vehicle 1 is a land-based electric vehicle 1. The photovoltaic cells 2 may be arranged on a roof and / or a side and / or a back of the vehicle 1 as well as on a front, in particular a front hatch.

[0039] Here and preferably, during sunshine a battery 3 of the vehicle 1 is charged by the photovoltaic cells 2. Depending on the orientation of the sun towards the vehicle 1 , different photovoltaic cells 2 may generate different amounts of energy.

[0040] Proposed is a method of testing at least one photovoltaic cell 2 of a solar charge arrangement 4 for a vehicle 1 using a test arrangement 5, wherein the test arrangement 5 comprises an optical sensor 6, in particular a camera 7. Fig. 1 shows the test arrangement 5 only schematically. The test arrangement 5 here and preferably comprises a dark chamber 8 in which a vehicle body part 9 comprising photovoltaic cells 2 is placed at a defined position, for example in a holder 10. The camera 7 is preferably placed at a defined position relative to the vehicle body part 9 to ensure a consistent quality of the images generated.

[0041] To test the photovoltaic cell 2, a reverse current 11 is applied to the at least one photovoltaic cell 2. Here and preferably, when a photovoltaic cell 2 is mentioned, several may be present and the reverse current 11 may be applied to several photovoltaic cells 2 at once. The solar charge arrangement 4 may comprise one or several strings 12 of photovoltaic cells 2. The strings 12 may be part of one or more arrays 13 of photovoltaic cells 2 of the solar charge arrangement 4.

[0042] In response to the reverse current 11 , the photovoltaic cell 2 emits light. The optical sensor 6 generates sensor data 14 by capturing the emitted light, in particular makes an image of the at least one photovoltaic cell 2, the image then being or forming part of the sensor data 14.

[0043] The test arrangement 5 comprises a control unit 15 for outputting and / or analyzing the sensor data 14, e.g. a computer. The solar charge arrangement 4 comprises a solar charge controller 16. The solar charge controller 16 controls the at least one photovoltaic cell 2. Specifically, the solar charge controller 16 controls the photovoltaic cell 2 while the photovoltaic cell 2 generates energy from sunlight. The control may comprise a maximum power point tracking.

[0044] Additionally, it is now the case that the solar charge controller 16 applies the reverse current 11 to the at least one photovoltaic cell 2. It is therefore the solar charge controller 16 which also takes part in controlling the charging via the photovoltaic cells 2 that enables the application of the reverse current 11 . For applying the reverse current 11 , the solar charge controller 16 may apply a specific voltage to the photovoltaic cell 2. The solar charge controller 16 may gradually increase a voltage applied to the photovoltaic cell 2 until reaching the specific voltage. The specific voltage may have been preconfigured and may depend on the specific type of photovoltaic cell 2. The specific voltage may also be set through a diagnostic interface of the test arrangement 5.

[0045] Additionally or alternatively, the solar charge controller 16 may gradually increase the current applied to the photovoltaic cell 2 until reaching a specific current. The light emitted by the photovoltaic cell 2 depends on the current and additionally, the current is preferably controlled to stay below a predefined maximum to protect the photovoltaic cell 2. Therefore it may generally be the case that the solar charge controller 16 controls the reverse current via a control loop.

[0046] Fig. 2a) shows a photovoltaic string 12 with several photovoltaic cells 2 and Fig. 2b) and Fig. 2c) each show a simplified equivalent circuit of a photovoltaic cell 2. In Fig. 2b), the photovoltaic cell 2 is generating energy. In Fig. 2c), the reverse current 11 is applied to the photovoltaic cell 2. "Reverse" here and preferably means that the voltage has the same polarity and the current flows in the opposite direction compared to the normal current flow in Fig. 2b). This operation is also known as “operation in the fourth quadrant”.

[0047] Fig. 3 shows schematically a solar charge controller 16, photovoltaic strings 12 controlled by the solar charge controller 16, a high volt battery 17 (HV battery 17) and a low volt battery 18 (LV battery 18). The batteries 3 are part of an electric vehicle 1 , the HV battery 17 being for example a 400 V or 800 V battery 3 and / or the LV battery 18 being for example a 12 V battery 3 or a 24 V battery 3 or a 48 V battery 3. If the vehicle 1 is not an electric vehicle 1 , the HV battery 17 will usually not be present and the solar charge controller 16 may be simplified.

[0048] Here and preferably, the solar charge controller 16 comprises a bidirectional DC-DC converter 19 and / or is an MPPT solar charge controller 16 which may comprise the bidirectional DC-DC converter 19. Using a bidirectional DC-DC converter 19 is an easy and cost-efficient way of providing the reverse current 11 . During a normal mode of use of the photovoltaic cells 2, the bidirectional DC-DC converter 19 converts a voltage from the photovoltaic cell 2 to a different voltage and conducts a current generated by the photovoltaic cell 2 and may adapt the power point of the string 12 according to a maximum power point tracking algorithm (MPPT).

[0049] Preferably, the solar charge controller 16 comprises a first stage bidirectional DC-DC converter 20 providing MPPT functionality and connected to the at least one photovoltaic cell 2. Fig. 3 shows this first stage bidirectional DC-DC converter 20.

[0050] Further, the solar charge controller 16 may comprise an LV second stage bidirectional DC-DC converter 21 for converting an output of the first stage bidirectional DC-DC converter 20 into 12 V or 24 V or 48 V or the like as the voltage of a board net of the vehicle 1 . Additionally or alternatively, the solar charge controller 16 may comprise an HV second stage bidirectional DC-DC converter 22 for converting an output of the first stage bidirectional DC-DC converter 20 into a high voltage of an electric vehicle 1 . The high voltage may be a voltage of at least 60 VDC.

[0051] The bidirectional DC-DC converter 19 or converters may also be used to generate a reverse current 11 for other use cases, for example to produce heat at or near the photovoltaic cells 2.

[0052] According to one embodiment it is proposed that a battery 3, in particular a vehicle battery 3, is connected to the solar charge arrangement 4 and provides the energy for the reverse current 11 , that a DC-DC converter of the solar charge arrangement 4, in particular the bidirectional DC-DC-converter, converts a voltage from the battery 3 into a different voltage.

[0053] Further it may be the case that a vehicle battery 3 is connected to the LV second stage bidirectional DC-DC converter 21 , the battery 3 then preferably being the LV battery 18, or the HV second stage bidirectional DC-DC converter 22, the battery 3 then preferably being the HV battery 17, and provides the energy for the reverse current 11. It may be the case that the HV battery 17 and the LV battery 18 are present but only one is connected to the solar charge controller 16 or only one provides the energy for the reverse current 11 . Preferably, the LV second stage bidirectional DC-DC converter 21 or the HV second stage bidirectional DC-DC converter 22 provides energy to the first stage bidirectional DC-DC converter 20 which generates the reverse current 11 .

[0054] According to one embodiment it is proposed that the solar charge arrangement 4 comprises several strings 12, each string 12 comprising at least one, preferably several, photovoltaic cells 2, that the solar charge arrangement 4 comprises multiple, in particular bidirectional, first stage DC-DC converters 20, in particular providing MPPT functionality and that each first stage DC-DC converter 20 controls at least one, preferably exactly one, string 12. Fig. 4, which may be an embodiment of Fig. 3, shows several arrays 13 with multiple strings 12 being controlled by one MPPT first stage bidirectional DC-DC converter 20 each. The connection to the battery 3 in Fig. 4 is only schematic, there may be one or more second stage DC-DC converters connected to the first stage DC- DC converters 20, here and preferably exactly one HV second stage bidirectional DC-DC converter 22 and one LV second stage bidirectional DC-DC converter 21 .

[0055] Preferably, the energy provided by the battery 3 is provided to more than one first stage bidirectional DC-DC converter 20 at once or successively. Several photovoltaic cells 2 may therefore be tested, preferably array 13 by array 13 or string 12 by string 12.

[0056] According to one embodiment it is proposed that the solar charge arrangement 4 comprises a vehicle 1 communication interface, in particular CAN interface, adapted to communicate in at least one direction, preferably bidirectionally, with a vehicle 1 . Fig. 3 shows a connection between the solar charge controller 16 and a vehicle central unit 23.

[0057] Preferably, the solar charge controller 16 is adapted to perform a function for charging a battery 3 of a vehicle 1 by interacting with vehicle 1 electronics, e.g. reading a signal from vehicle 1 electronics or sending a signal to vehicle 1 electronics. Actually doing so may also be part of the proposed method.

[0058] Fig. 5 shows a retrofit solar charge arrangement 4 and the system boundaries towards the vehicle 1 . In this case, the vehicle 1 is a combustion engine vehicle 1. Fig. 5 shows the preferred interfaces of the solar charge controller 16. As shown in Fig. 5 but also independently, it may be the case that the solar charge controller 16 comprises a telemetry interface 24 adapted to communicate with a control unit 15 external to the vehicle 1. The telemetry interface 24 may be integrated into the solar charge controller 16 or may be a separate component from a microcontroller of the solar charge controller 16 which is here conceptually assigned to the solar charge controller 16. The external control unit 15 may be plugged into a maintenance interface of the vehicle 1 . Alternatively, the communication can also be wireless.

[0059] Preferably, the control unit 15 is part of the test arrangement 5. Additionally or alternatively, the control unit 15 may send a test command to the solar charge arrangement 4 and the solar charge arrangement 4 generates the reverse current 11 in response to the test command.

[0060] Fig. 5 shows on the right side several arrays 13 of photovoltaic cells 2 connected to the solar charge controller 16 on the left. The solar charge controller 16 comprises a telemetry interface 24, a connection to the vehicle battery 3 for charging the vehicle battery 3 and receiving energy and several first stage bidirectional DC / DC converters which are not shown. A second stage DC / DC converter is optional. The solar charge controller 16 also comprises an interface for communicating with the vehicle 1. This may for example be a CAN interface. Alternatively or additionally to being a CAN interface, the interface for communicating with the vehicle 1 may also comprise a clamp 15 interface for reading a signal on the clamp 15 and / or an interface for sensing a voltage of the LV battery 18. According to one embodiment it is proposed that the photovoltaic cell 2 is embedded in a vehicle part 9, in particular vehicle body part 9 or retrofit vehicle part 9, preferably, that the vehicle part 9 has been produced by overmolding the at least one photovoltaic cell 2.

[0061] Turning back to Fig. 1 , it may be the case that the test arrangement 5 comprises a dark chamber 8, that the photovoltaic cell 2 is placed in the dark chamber 8 and that the sensor data 14 is generated while the photovoltaic cell 2 is in the dark chamber 8.

[0062] The testing may be performed as an end of line test, in particular before the solar charge arrangement 4 is mounted to the vehicle 1 , and / or as a maintenance test after the solar charge arrangement 4 has been mounted to the vehicle 1 . Preferably, the testing is repeated as part of a regular maintenance.

[0063] Alternatively to using a dark chamber 8, the sensor data 14 may be generated at night. It may also be the case that the camera 7 is mounted on a drone. In particular for an end of line test, an external battery 3 may be connected to the solar charge controller 16.

[0064] The sensor data 14 of at least two tests may be compared to identify changes over time. The result of an end of line testing may be saved and compared to the result of a test during a regular maintenance or in case of a problem. The sensor data 14 of an end of line test may also serve as a calibration point for an automatic analysis of the sensor data 14. If a photovoltaic cell 2 is identified to be defective, the respective photovoltaic cell 2, string 12, array 13 or vehicle part 9 may be replaced.

[0065] According to one embodiment it is proposed that a processing unit 25, in particular a microcontroller, of the solar charge arrangement 4 provides one or more functionalities of enabling communication with the vehicle 1 , in particular so that the vehicle 1 allows power to be drawn from the vehicle battery 3, control power drawn from the vehicle battery 3, control step down from high voltage to intermediate voltage via the HV second stage bidirectional DC-DC converter 22, control step up or step down from intermediate voltage to the photovoltaic cell 2 via the first stage bidirectional DC-DC converter 20, control step up or step down from low voltage to intermediate voltage via the LV second stage bidirectional DC-DC converter 21 , increase voltage and current output to the photovoltaic cell 2 until a pre-defined voltage and / or current is achieved at the photovoltaic cell 2 for electroluminescence, ensure that the reverse current 11 stays below a maximum current of the photovoltaic cell 2.

[0066] It should be understood that the reverse current 11 may be split onto several photovoltaic cells 2 and in that case a maximum current may be defined per string 12 or array 13 instead of per photovoltaic cell 2.

[0067] To enhance the detection of faulty photovoltaic cells 2, the solar charge controller 16 may apply the reverse current 11 as a defined current and measure the voltage applied or apply a defined voltage and measures the current applied. The solar charge arrangement 4 or the test arrangement 5 may compare the measured current or voltage with a specified voltage or current to identify a fault of the photovoltaic cell 2. A defective photovoltaic cell 2 may draw less or more current than it should.

[0068] Another teaching which is of equal importance relates to a solar charge controller 16 adapted to control at least one photovoltaic cell 2, wherein the solar charge controller 16 controls the photovoltaic cell 2 while the photovoltaic cell 2 generates energy from sunlight.

[0069] Essential according to this further teaching is that the solar charge controller 16 applies a reverse current 11 to the at least one photovoltaic cell 2 such that the photovoltaic cell 2 in response to the reverse current 11 emits light. The solar charge controller 16 is preferably adapted to be used in the proposed method.

[0070] All explanations given with regard to the proposed method are fully applicable. Another teaching which is of equal importance relates to a solar charge arrangement 4 comprising at least one photovoltaic cell 2 and a proposed solar charge controller 16. The solar charge arrangement 4 is preferably adapted to be used in the proposed method.

[0071] All explanations given with regard to the proposed method and the proposed solar charge controller 16 are fully applicable.

[0072] Another teaching which is of equal importance relates to a vehicle 1 comprising a proposed solar charge arrangement 4.

[0073] All explanations given with regard to the proposed method, the proposed solar charge controller 16 and the proposed solar charge arrangement 4 are fully applicable.

[0074] Another teaching which is of equal importance relates to a test arrangement 5 adapted to communicate with a proposed solar charge controller 16, wherein the test arrangement 5 comprises an optical sensor 6, in particular a camera 7, wherein the optical sensor 6 generates sensor data 14 by capturing emitted light, in particular makes an image of the at least one photovoltaic cell 2, wherein the test arrangement 5 comprises a control unit 15 for outputting and / or analyzing the sensor data 14. The test arrangement 5 may be adapted to send the test command.

[0075] All explanations given with regard to the proposed method, the proposed solar charge controller 16, the proposed solar charge arrangement 4 and the proposed vehicle 1 are fully applicable.

Claims

Claims1 . Method of testing at least one photovoltaic cell (2) of a solar charge arrangement (4) for a vehicle (1 ) using a test arrangement (5), wherein the test arrangement (5) comprises an optical sensor (6), in particular a camera (7), wherein a reverse current (11 ) is applied to the at least one photovoltaic cell (2), wherein the photovoltaic cell (2) in response to the reverse current (11 ) emits light, wherein the optical sensor (6) generates sensor data (14) by capturing the emitted light, in particular makes an image of the at least one photovoltaic cell (2), wherein the test arrangement (5) comprises a control unit (15) for outputting and / or analyzing the sensor data (14), wherein the solar charge arrangement (4) comprises a solar charge controller (16), wherein the at least one photovoltaic cell (2) is controlled by the solar charge controller (16), wherein the solar charge controller (16) controls the photovoltaic cell (2) while the photovoltaic cell (2) generates energy from sunlight, wherein the solar charge controller (16) applies the reverse current (11 ) to the at least one photovoltaic cell (2).

2. Method according to claim 1 , characterized in that the solar charge controller (16) comprises a bidirectional DC-DC converter (19) and / or is an MPPT solar charge controller (16), preferably, that the solar charge controller (16) comprises a first stage bidirectional DC-DC converter (20) providing MPPT functionality and connected to the at least one photovoltaic cell (2), that the solar charge controller (16) comprises an LV second stage bidirectional DC-DC converter (21 ) for converting an output of the first stage bidirectional DC-DC converter (20) into 12 V or 24 V or 48 V as the voltage of a board net of the vehicle (1 ), and / or, that the solar charge controller (16) comprises an HV second stage bidirectional DC-DC converter (22) for converting an output of the first stage bidirectional DC-DC converter (20) into a high voltage of an electric vehicle (1 ).

3. Method according to claim 1 or 2, characterized in that a battery (3), in particular a vehicle battery (3), is connected to the solar charge arrangement (4) and provides the energy for the reverse current (11 ), that a DC-DC converterof the solar charge arrangement (4), in particular the bidirectional DC-DC-con- verter, converts a voltage from the battery (3) into a different voltage,4. Method according to claim 3, characterized in that a vehicle battery (3) is connected to the LV second stage bidirectional DC-DC converter (21 ) or the HV second stage bidirectional DC-DC converter (22) and provides the energy for the reverse current (11 ), preferably, that the LV second stage bidirectional DC-DC converter (21 ) or the HV second stage bidirectional DC-DC converter (22) provides energy to the first stage bidirectional DC-DC converter (20) which generates the reverse current (11 ).

5. Method according to one of the preceding claims, characterized in that the solar charge arrangement (4) comprises several strings (12), each string (12) comprising at least one, preferably several, photovoltaic cells (2), that the solar charge arrangement (4) comprises multiple, in particular bidirectional, first stage DC-DC converters (20), in particular providing MPPT functionality, that each first stage DC-DC converter (20) controls at least one, preferably exactly one, string (12), preferably, that the energy provided by the battery (3) is provided to more than one first stage bidirectional DC-DC converter (20) at once or successively.

6. Method according to one of the preceding claims, characterized in that the solar charge arrangement (4) comprises a vehicle (1 ) communication interface, in particular CAN interface, adapted to communicate in at least one direction, preferably bidirectionally, with a vehicle (1 ), preferably, that the solar charge controller (16) is adapted to perform a function for charging a battery (3) of a vehicle (1 ) by interacting with vehicle (1 ) electronics, e.g. reading a signal from vehicle (1 ) electronics or sending a signal to vehicle (1 ) electronics.

7. Method according to one of the preceding claims, characterized in that the solar charge controller (16) comprises a telemetry interface (24) adapted to communicate with a control unit (15) external to the vehicle (1 ), preferably, that the control unit (15) is part of the test arrangement (5), and / or, that the control unit (15) sends a test command to the solar charge arrangement (4) and the solar charge arrangement (4) generates the reverse current (11 ) in response to the test command.

8. Method according to one of the preceding claims, characterized in that the photovoltaic cell (2) is embedded in a vehicle part (9), in particular vehicle body part (9) or retrofit vehicle part (9), preferably, that the vehicle part (9) has been produced by overmolding the at least one photovoltaic cell (2).

9. Method according to one of the preceding claims, characterized in that the test arrangement (5) comprises a dark chamber (8), that the photovoltaic cell (2) is placed in the dark chamber (8), that the sensor data (14) is generated while the photovoltaic cell (2) is in the dark chamber (8), and / or, that the testing is performed as an end of line test, in particular before the solar charge arrangement (4) is mounted to the vehicle (1 ), and / or as a maintenance test after the solar charge arrangement (4) has been mounted to the vehicle (1 ), preferably, that the testing is repeated as part of a regular maintenance.

10. Method according to one of the preceding claims, characterized in that a processing unit (25), in particular a microcontroller, of the solar charge arrangement (4) provides one or more functionalities of enabling communication with the vehicle (1 ), in particular so that the vehicle(1 ) allows power to be drawn from the vehicle battery (3), control power drawn from the vehicle battery (3), control step down from high voltage to intermediate voltage via the HV second stage bidirectional DC-DC converter (22), control step up or step down from intermediate voltage to the photovoltaic cell(2) via the first stage bidirectional DC-DC converter (20), control step up or step down from low voltage to intermediate voltage via the LV second stage bidirectional DC-DC converter (21 ), increase voltage and current output to the photovoltaic cell (2) until a pre-defined voltage and / or current is achieved at the photovoltaic cell (2) for electroluminescence, ensure that the reverse current (11 ) stays below a maximum current of the photovoltaic cell (2).11 . Method according to one of the preceding claims, characterized in that the solar charge controller (16) applies the reverse current (11 ) as a defined current and measures the voltage applied or applies a defined voltage andmeasures the current applied, that the solar charge arrangement (4) compares the measured current or voltage with a specified voltage or current to identify a fault of the photovoltaic cell (2).

12. Solar charge controller adapted to control at least one photovoltaic cell (2), wherein the solar charge controller (16) controls the photovoltaic cell (2) while the photovoltaic cell (2) generates energy from sunlight, characterized in that the solar charge controller (16) applies a reverse current (11 ) to the at least one photovoltaic cell (2) such that the photovoltaic cell (2) in response to the reverse current (11 ) emits light.

13. Solar charge arrangement comprising at least one photovoltaic cell (2) and a solar charge controller (16) according to claim 12.

14. Vehicle comprising a solar charge arrangement (4) according to claim 13.

15. Test arrangement adapted to communicate with a solar charge controller (16) according to claim 12, wherein the test arrangement (5) comprises an optical sensor (6), in particular a camera (7), wherein the optical sensor (6) generates sensor data (14) by capturing emitted light, in particular makes an image of the at least one photovoltaic cell (2), wherein the test arrangement (5) comprises a control unit (15) for outputting and / or analyzing the sensor data

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