> Quick answer: As the operating temperature of a solar panel increases, its voltage output significantly decreases while current increases slightly [1][5]. This results in reduced power output, affecting charging efficiency more in summer due to lower voltage. In winter, while panels perform better, batteries suffer from cold-induced capacity reduction.
The relationship between solar panel operating temperature and its electrical output is a critical factor for the performance of any solar-powered device, particularly solar lamps used in Romania. This article delves into how seasonal changes affect charging efficiency by examining both the impact on the solar panels themselves and the batteries they charge.
The Role of Temperature on Solar Panel Efficiency
Solar panels exhibit an inverse relationship between temperature and voltage output: as temperatures rise, voltage drops significantly while current increases only slightly [1][5]. This inverse relationship is due to changes in semiconductor properties within the photovoltaic cells. While solar panels absorb more heat during summer months, this increased temperature negatively impacts their electrical performance rather than their ability to capture sunlight.
The magnitude of power reduction per degree Celsius increase can be quantified by the temperature coefficient, typically ranging from 0.5% to 4% [5][6]. For example, a panel with a 4% temperature coefficient will lose 4% of its output for every degree above 25°C [5].
Seasonal Charging Challenges
Summer Conditions
In summer, solar panels often operate at temperatures up to 36°F (20°C) higher than ambient and can reach extreme temperatures like 149°F (65°C) in hot climates [6]. This significant temperature increase causes a substantial drop in voltage output, leading to reduced power generation. The maximum power point voltage (Vmpp) shifts downward with increasing temperature, potentially falling below the required charging voltage for batteries [5][10][12][17][21].
This temperature-induced voltage drop can be problematic, especially when panels are directly connected to batteries without intermediate converters. If the output voltage is too low, efficient or even any battery charging becomes impossible despite ample sunlight [10][12][17][21].
Winter Conditions
Conversely, winter presents a different set of challenges. Lower temperatures improve panel voltage output, but overall energy harvest decreases due to shorter daylight hours and reduced solar irradiance [5]. The primary concern in winter is not the reduced efficiency of the solar panels themselves but rather the diminished performance of batteries.
Batteries are known to suffer from reduced capacity at cold temperatures. At 0°F (-18°C), a battery’s capacity can drop to half its nominal value, which is typically 78°F (25°C) [7]. Charging in cold conditions also requires higher voltage levels, and if the battery is discharged below 80% capacity, it risks freezing and bursting at -7.8°C (18°F) [7].
Balancing Panel and Battery Performance
The interplay between solar panel and battery performance highlights the importance of intelligent system design to manage these temperature effects. For example:
- High thermal management in summer can prevent overheating but may lead to poor winter performance due to reduced charging efficiency.
- Battery warming strategies, such as placing the battery near the panel, help maintain battery warmth during cold weather but risk overheating during hot summers [14].
Key Takeaways
- Solar panels lose voltage and power output with increasing temperature, significantly impacting summer charging efficiency.
- Batteries perform poorly in winter due to reduced capacity at low temperatures, even though solar panel performance improves.
- Intelligent system design is crucial for balancing the competing effects of temperature on both solar panels and batteries.
Comparison Table: Summer vs Winter Performance
| Feature | Summer (High Temp) | Winter (Low Temp) |
|–––––––––|––––––––|––––––––-|
| Solar Panel Voltage | Decreases Significantly| Increases |
| Overall Power Output | Reduced | Relatively Higher |
| Battery Charging | Inefficient or Impractical| More Efficient but Low Capacity |
Frequently Asked Questions
[{„q”: „Why do solar panels lose efficiency in high temperatures?”, „a”: „Solar panels lose efficiency at higher temperatures due to fundamental semiconductor physics, where increased heat causes a drop in voltage output [1][5].”},
{„q”: „How does cold weather affect battery performance?”, „a”: „Cold temperatures reduce the capacity of batteries, with their capacity dropping by half at -18°C (0°F) compared to 25°C [7]. This impacts charging efficiency and overall system performance.”},
{„q”: „What is a temperature coefficient in solar panels?”, „a”: „The temperature coefficient quantifies how much power output decreases per degree Celsius increase above the standard test condition of 25°C, typically ranging from 0.5% to 4% [5][6].”}]
References
- [1] Solar_Photovoltaic_Performance_and_Efficiency_Basics__974f2aa6 — authority
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heat. – Temperature—Solar cells generally work best at low temperatures. Higher temperatures cause the semiconductor properties to shift, resulting in a slight increase in current, but a much larger decrease in voltage. Extreme increases in temperature can also damage the cell and other module materials, leading to shorter operating lifetimes. Since much of the sunlight shining on cells becomes heat, proper thermal management improves both efficiency and lifetime. – Reflection—A cell's efficiency can be increased by minimizing the amount of light reflected away from the cell's surface. For example, untreated silicon reflects more than 30% of incident light. Anti-reflection coatings and textured surfaces help decrease reflection. A high-efficiency cell will appear dark blue or black. Determining Conversion Efficiency Researchers measure the performance of a PV device to predict the power the cell will produce. Electrical power is the product of current and voltage. Current-voltage relationships measure the electrical characteristics of PV devices. If a certain "load" resistance is connected to the two terminals of a cell or module, the current and voltage being produced will adjust according to Ohm's law (the current through a conductor between two points is directly proportional to the potential difference across the two points). Efficiencies are obtained by exposing the cell to a constant, standard level of light while maintaining a constant cell temperature, and measuring t
- [5] Projects_With_Everyday_Dave__HEAT_-The_Enemy_of_SOLAR-_Are_Vertical_Solar_Panels_Better__Tr8llj-0Fjw — youtube
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how much energy it takes to push them out where they can move around gets lower and as this band Gap energy decreases the energy of the photons that can push it up there also decreases so if we're getting the same number of photons coming in from the Sun if we only absorb the lower energy parts of them we're going to get less energy overall well I hope that's as helpful for you as it was for me the reality is the higher energy in the Silicon we can't absorb As Much from the Sun yep okay so moving on the temperature effect is well documented in the industry and most panels come with a temperature coefficient rating the units for solar panels temperature coefficient is typically expressed as percent power per degree Celsius this indicates the percentage change in the solar panels performance usually power output for every degree Celsius in temperature change above or below the standard test condition which is 25° C or 77° F because all the specs are in Celsius and all the calculations are in Celsius I'll be doing all of today's analysis in Celsius apologies to those who love Freedom Units this rating typically varies from 3% per degree Celsius to 0.5% per degree Celsius for example in today's data I have temperatures that range from 10° CSUS in the morning to 50° C in the afternoon or a 40° swing in temperature change if if we assume a 400W panel with a coefficient of 4% per degree C we would see a 16% change in performance over that temperature swing typically we don't notice
- [6] How_hot_do_solar_panels_get_and_how_does_it_affect_my_system__3483098b — authority
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are absorbing the sun’s heat, and because they are built to be tough, high temperatures will not degrade them. Are solar panels hot to the touch? Yes, solar panels are hot to the touch. Generally speaking, solar panels are 36 degrees Fahrenheit warmer than the ambient external air temperature. When solar panels get hot, the operating cell temperature is what increases and reduces the ability for panels to generate electricity. Because the panels are a dark color, they are hotter than the external temperature because dark colors, like black, absorb more heat. For example, the ambient temperature in the desert can reach 113 degrees Fahrenheit, meaning solar panels in this climate can reach 149 degrees Fahrenheit. The physical panel and metal racking that secure them in place are definitely not meant to be touched on a particularly hot day. What is the ‘temperature coefficient’? The temperature coefficient is the percentage decrease in energy production for each increase in degree Celsius over 25, or 77 degrees Fahrenheit. A low temperature coefficient is best. The reduction in output is minimal, only about .5%, so you will probably not notice your solar panels performing any worse. For reference, the temperature coefficient from major solar panel manufacturers’ data sheets is below. For example, let’s say you have the Sunpower module and the solar cell temperature is measured at 45 degrees C. That’s 20 degrees C above STC. To find how much the power output will decrease, you mu
- [7] Exploring_the_Influence_of_Temperature_on_Battery_Charging__c19fe45e — authority
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# Exploring the Influence of Temperature on Battery Charging Source: Blog/Web URL: https://insights.acuitybrands.com/product-updates-blog/exploring-the-influence-of-temperature-on-battery-charging Author: Matt Pang Date: 2023-12-19 Did you know that temperatures play a critical role in battery charging? The efficiency of your battery’s charge and discharge cycles, its output capacity, and even its overall lifespan can be significantly influenced by the temperature. Whether it’s the sweltering heat of summer or the freezing cold of winter, each degree can make a difference. How do cold and heat affect my battery? Batteries perform best at an ideal temperature of 78 degrees Fahrenheit. When the temperature rises, batteries tend to lose charge more quickly due to increased self-discharge. On the other hand, cooler temperatures slow down this self-discharge process, but at the cost of reducing the battery’s output capacity. For instance, at the freezing point (0 degrees Fahrenheit), a battery’s capacity drops to half of what it would be at the nominal temperature of 78 degrees Fahrenheit. Furthermore, a battery that has been depleted to 80% of its capacity is susceptible to freezing and bursting at 18 degrees Fahrenheit. How does the temperature affect battery charging? Charging a battery to its full capacity in cold conditions requires a higher voltage. It’s crucial that the charging voltage adapts to the surrounding temperature of the battery to not only guarantee a complete ch
- [10] US20250253703A1_-_Method_for_directly_charging_battery__c5959e18 — patent
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it is discovered that in the latest unit time interval there are severe or violent weather changes, it is determined that the battery is not adapted to be charged. – the latest weather change conditions such as the ambient temperature, the illuminance and the like – the maximum power point voltage is generally low on cloudy days, the maximum power point voltage cannot match the desired battery charging voltage even though the number of series-connected photovoltaic panels is adjusted to a maximum value, whereupon the secondary battery is not adapted to be directly charged, and the reminding information is triggered to be generated and displayed. – step S 2 judging whether the target number of series-connected photovoltaic panels is equal to the current number of series-connected photovoltaic panels, if YES, executing step S 4 , otherwise, executing step S 3 . – step S 2 for example, if the target number of series-connected photovoltaic panels is 6 and the current number of series-connected photovoltaic panels is also 6 , it is not necessary to adjust the number of series-connected photovoltaic panels of each of the photovoltaic panel series branches, and the process may jump to step S 3 , otherwise performing step S 3 to adjust the number of series-connected photovoltaic panels of each of the photovoltaic panel series branches. – step S 3 generating a first control signal according to the target number of series-connected photovoltaic panels, and transmitting the first contro
- [12] CN115425732A_-_Direct_battery_charging_method_device_system__a08a7f92 — patent
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the maximum power point voltage of each photovoltaic panel series branch recorded in the latest unit period can reflect the latest weather changes (such as ambient temperature and illuminance, etc.), if it is found that there is If the weather changes badly or violently, it can be deemed not suitable for charging. For example, the maximum power point voltage on cloudy days will generally be low. When it is not suitable to directly charge the secondary battery, the generation and display of the reminder message will be triggered. S2.判断所述光伏板串联目标数是否等于所述当前光伏板串联数，若是，则执行步骤S4，否则执行步骤S3。S2. Determine whether the target number of photovoltaic panels connected in series is equal to the current number of photovoltaic panels connected in series, if yes, execute step S4, otherwise execute step S3. 在所述步骤S2中，举例的，若所述光伏板串联目标数为6，所述当前光伏板串联数也为6，则无需调整所述各个光伏板串联支路的光伏板串联数，可跳过步骤S3，反之就需要执行步骤S3来调整所述各个光伏板串联支路的光伏板串联数。In the step S2, for example, if the target number of photovoltaic panels connected in series is 6, and the current number of photovoltaic panels connected in series is also 6, there is no need to adjust the number of photovoltaic panels connected in series in each branch of photovoltaic panels connected in series. Step S3 is skipped, otherwise step S3 needs to be executed to adjust the number of photovoltaic panels connected in series in each photovoltaic panel series branch. S3.根据所述光伏板串联目标数，生成第一控制信号，并将所述第一控制信号传送至所述光伏板电压转换电路，以便所述光伏板电压转换电路在响应所述第一控制信号后，使所述各条光伏板串联支路的光伏板串联数分别调整至所述光伏板串联目标数，然后执行步骤S
- [14] US5367442A_-_Self-contained_solar_powered_lamp_-_Google_Patents__17774f1c — patent
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specified by the manufacturer. At temperatures higher than the operating temperature, the charge acceptance capabilities of the electrical storage device decrease substantially. This is undesirable because sunlight to power the solar cell array is available only during a relatively short period of time each day. The current level generated by the solar cell array when in excess of the charge acceptance of the electrical storage device causes it to overheat and sustain damage, thereby causing the overall performance of the solar powered lamp to deteriorate. In one approach to overcome this problem, the electrical storage device may be arranged remote from the solar cell array. Although this prevents the electrical storage device from absorbing heat generated by the solar cell array, thus, maintaining the operating temperature at a normal level in hot weather, it is not satisfactory during cold weather because the electrical storage device is unable to provide current sufficient to illuminate the bulb at temperatures below its operating temperature. The electrical storage device is therefore typically placed in heat transfer proximity to the solar cell array so that heat absorbed by the solar cell array on a sunny day helps elevate the temperature of the power source to its normal operating temperature even if the ambient temperature is low. Moreover, existing solar lighting devices are configured in a manner which does not provide for the flow of air through the lamp. This fur
- [17] US20250253703A1_-_Method_for_directly_charging_battery__c5959e18 — patent
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battery charging voltage according to the desired battery charging voltage of the secondary battery and the current maximum power point voltage of the individual photovoltaic panel. – the current maximum power point voltage which is also an interval value with an upper and lower offset range, such as [38V,42V] – the target number of series-connected photovoltaic panels is 6. Therefore, the target number of the series-connected photovoltaic panels needed currently can be accurately determined through the construction and application of the voltage linear database (namely, the current maximum power point voltage of an individual photovoltaic panel). – step S 1 specifically, the step of, according to a desired battery charging voltage of the secondary battery, a current number of series-connected photovoltaic panels and a current maximum power point voltage of each of the photovoltaic panel series branches, determining a target number of series-connected photovoltaic panels which are of the photovoltaic panel series branch and enable the maximum power point voltage to match the desired battery charging voltage includes but not limited to: judging whether the secondary battery can be charged according to the maximum power point voltage of each photovoltaic panel series branch as recorded in the latest unit time period; if YES, determining the target number of series-connected photovoltaic panels which are of the photovoltaic panel series branch and enable the maximum power point
- [21] WO2024017031A1_-_Battery_direct-charging_method_and_apparatus__0fca7623 — patent
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S1, specifically, according to the battery charging demand voltage of the secondary battery, the current number of photovoltaic panels in series and the current maximum power point voltage of each photovoltaic panel series branch, the series connection of the photovoltaic panels is determined. The target number of photovoltaic panels in series of the branch and making the maximum power point voltage match the battery charging demand voltage, including but not limited to: based on the maximum power of each photovoltaic panel series branch recorded in the most recent unit period point voltage to determine whether the secondary battery can be charged; if so, based on the battery charging demand voltage of the secondary battery and the current number of photovoltaic panels in series and the current maximum power point of each photovoltaic panel series branch. Voltage, determine the target number of photovoltaic panels in series of the photovoltaic panel series branch and make the maximum power point voltage match the battery charging demand voltage, otherwise trigger the generation and display of a reminder message indicating that it is not currently rechargeable. Specifically, the most recent unit period may be, but is not limited to, the most recent 1 minute, the most recent 3 minutes, the most recent 10 minutes, etc. Since the maximum power point voltage of each photovoltaic panel series branch recorded in the latest unit period can reflect recent weather changes (such as ambi
heat. – Temperature—Solar cells generally work best at low temperatures. Higher temperatures cause the semiconductor properties to shift, resulting in a slight increase in current, but a much larger decrease in voltage. Extreme increases in temperature can also damage the cell and other module materials, leading to shorter operating lifetimes. Since much of the sunlight shining on cells becomes heat, proper thermal management improves both efficiency and lifetime. – Reflection—A cell's efficiency can be increased by minimizing the amount of light reflected away from the cell's surface. For example, untreated silicon reflects more than 30% of incident light. Anti-reflection coatings and textured surfaces help decrease reflection. A high-efficiency cell will appear dark blue or black. Determining Conversion Efficiency Researchers measure the performance of a PV device to predict the power the cell will produce. Electrical power is the product of current and voltage. Current-voltage relationships measure the electrical characteristics of PV devices. If a certain "load" resistance is connected to the two terminals of a cell or module, the current and voltage being produced will adjust according to Ohm's law (the current through a conductor between two points is directly proportional to the potential difference across the two points). Efficiencies are obtained by exposing the cell to a constant, standard level of light while maintaining a constant cell temperature, and measuring t
how much energy it takes to push them out where they can move around gets lower and as this band Gap energy decreases the energy of the photons that can push it up there also decreases so if we're getting the same number of photons coming in from the Sun if we only absorb the lower energy parts of them we're going to get less energy overall well I hope that's as helpful for you as it was for me the reality is the higher energy in the Silicon we can't absorb As Much from the Sun yep okay so moving on the temperature effect is well documented in the industry and most panels come with a temperature coefficient rating the units for solar panels temperature coefficient is typically expressed as percent power per degree Celsius this indicates the percentage change in the solar panels performance usually power output for every degree Celsius in temperature change above or below the standard test condition which is 25° C or 77° F because all the specs are in Celsius and all the calculations are in Celsius I'll be doing all of today's analysis in Celsius apologies to those who love Freedom Units this rating typically varies from 3% per degree Celsius to 0.5% per degree Celsius for example in today's data I have temperatures that range from 10° CSUS in the morning to 50° C in the afternoon or a 40° swing in temperature change if if we assume a 400W panel with a coefficient of 4% per degree C we would see a 16% change in performance over that temperature swing typically we don't notice
are absorbing the sun’s heat, and because they are built to be tough, high temperatures will not degrade them. Are solar panels hot to the touch? Yes, solar panels are hot to the touch. Generally speaking, solar panels are 36 degrees Fahrenheit warmer than the ambient external air temperature. When solar panels get hot, the operating cell temperature is what increases and reduces the ability for panels to generate electricity. Because the panels are a dark color, they are hotter than the external temperature because dark colors, like black, absorb more heat. For example, the ambient temperature in the desert can reach 113 degrees Fahrenheit, meaning solar panels in this climate can reach 149 degrees Fahrenheit. The physical panel and metal racking that secure them in place are definitely not meant to be touched on a particularly hot day. What is the ‘temperature coefficient’? The temperature coefficient is the percentage decrease in energy production for each increase in degree Celsius over 25, or 77 degrees Fahrenheit. A low temperature coefficient is best. The reduction in output is minimal, only about .5%, so you will probably not notice your solar panels performing any worse. For reference, the temperature coefficient from major solar panel manufacturers’ data sheets is below. For example, let’s say you have the Sunpower module and the solar cell temperature is measured at 45 degrees C. That’s 20 degrees C above STC. To find how much the power output will decrease, you mu
# Exploring the Influence of Temperature on Battery Charging Source: Blog/Web URL: https://insights.acuitybrands.com/product-updates-blog/exploring-the-influence-of-temperature-on-battery-charging Author: Matt Pang Date: 2023-12-19 Did you know that temperatures play a critical role in battery charging? The efficiency of your battery’s charge and discharge cycles, its output capacity, and even its overall lifespan can be significantly influenced by the temperature. Whether it’s the sweltering heat of summer or the freezing cold of winter, each degree can make a difference. How do cold and heat affect my battery? Batteries perform best at an ideal temperature of 78 degrees Fahrenheit. When the temperature rises, batteries tend to lose charge more quickly due to increased self-discharge. On the other hand, cooler temperatures slow down this self-discharge process, but at the cost of reducing the battery’s output capacity. For instance, at the freezing point (0 degrees Fahrenheit), a battery’s capacity drops to half of what it would be at the nominal temperature of 78 degrees Fahrenheit. Furthermore, a battery that has been depleted to 80% of its capacity is susceptible to freezing and bursting at 18 degrees Fahrenheit. How does the temperature affect battery charging? Charging a battery to its full capacity in cold conditions requires a higher voltage. It’s crucial that the charging voltage adapts to the surrounding temperature of the battery to not only guarantee a complete ch
it is discovered that in the latest unit time interval there are severe or violent weather changes, it is determined that the battery is not adapted to be charged. – the latest weather change conditions such as the ambient temperature, the illuminance and the like – the maximum power point voltage is generally low on cloudy days, the maximum power point voltage cannot match the desired battery charging voltage even though the number of series-connected photovoltaic panels is adjusted to a maximum value, whereupon the secondary battery is not adapted to be directly charged, and the reminding information is triggered to be generated and displayed. – step S 2 judging whether the target number of series-connected photovoltaic panels is equal to the current number of series-connected photovoltaic panels, if YES, executing step S 4 , otherwise, executing step S 3 . – step S 2 for example, if the target number of series-connected photovoltaic panels is 6 and the current number of series-connected photovoltaic panels is also 6 , it is not necessary to adjust the number of series-connected photovoltaic panels of each of the photovoltaic panel series branches, and the process may jump to step S 3 , otherwise performing step S 3 to adjust the number of series-connected photovoltaic panels of each of the photovoltaic panel series branches. – step S 3 generating a first control signal according to the target number of series-connected photovoltaic panels, and transmitting the first contro
the maximum power point voltage of each photovoltaic panel series branch recorded in the latest unit period can reflect the latest weather changes (such as ambient temperature and illuminance, etc.), if it is found that there is If the weather changes badly or violently, it can be deemed not suitable for charging. For example, the maximum power point voltage on cloudy days will generally be low. When it is not suitable to directly charge the secondary battery, the generation and display of the reminder message will be triggered. S2.判断所述光伏板串联目标数是否等于所述当前光伏板串联数，若是，则执行步骤S4，否则执行步骤S3。S2. Determine whether the target number of photovoltaic panels connected in series is equal to the current number of photovoltaic panels connected in series, if yes, execute step S4, otherwise execute step S3. 在所述步骤S2中，举例的，若所述光伏板串联目标数为6，所述当前光伏板串联数也为6，则无需调整所述各个光伏板串联支路的光伏板串联数，可跳过步骤S3，反之就需要执行步骤S3来调整所述各个光伏板串联支路的光伏板串联数。In the step S2, for example, if the target number of photovoltaic panels connected in series is 6, and the current number of photovoltaic panels connected in series is also 6, there is no need to adjust the number of photovoltaic panels connected in series in each branch of photovoltaic panels connected in series. Step S3 is skipped, otherwise step S3 needs to be executed to adjust the number of photovoltaic panels connected in series in each photovoltaic panel series branch. S3.根据所述光伏板串联目标数，生成第一控制信号，并将所述第一控制信号传送至所述光伏板电压转换电路，以便所述光伏板电压转换电路在响应所述第一控制信号后，使所述各条光伏板串联支路的光伏板串联数分别调整至所述光伏板串联目标数，然后执行步骤S
specified by the manufacturer. At temperatures higher than the operating temperature, the charge acceptance capabilities of the electrical storage device decrease substantially. This is undesirable because sunlight to power the solar cell array is available only during a relatively short period of time each day. The current level generated by the solar cell array when in excess of the charge acceptance of the electrical storage device causes it to overheat and sustain damage, thereby causing the overall performance of the solar powered lamp to deteriorate. In one approach to overcome this problem, the electrical storage device may be arranged remote from the solar cell array. Although this prevents the electrical storage device from absorbing heat generated by the solar cell array, thus, maintaining the operating temperature at a normal level in hot weather, it is not satisfactory during cold weather because the electrical storage device is unable to provide current sufficient to illuminate the bulb at temperatures below its operating temperature. The electrical storage device is therefore typically placed in heat transfer proximity to the solar cell array so that heat absorbed by the solar cell array on a sunny day helps elevate the temperature of the power source to its normal operating temperature even if the ambient temperature is low. Moreover, existing solar lighting devices are configured in a manner which does not provide for the flow of air through the lamp. This fur
battery charging voltage according to the desired battery charging voltage of the secondary battery and the current maximum power point voltage of the individual photovoltaic panel. – the current maximum power point voltage which is also an interval value with an upper and lower offset range, such as [38V,42V] – the target number of series-connected photovoltaic panels is 6. Therefore, the target number of the series-connected photovoltaic panels needed currently can be accurately determined through the construction and application of the voltage linear database (namely, the current maximum power point voltage of an individual photovoltaic panel). – step S 1 specifically, the step of, according to a desired battery charging voltage of the secondary battery, a current number of series-connected photovoltaic panels and a current maximum power point voltage of each of the photovoltaic panel series branches, determining a target number of series-connected photovoltaic panels which are of the photovoltaic panel series branch and enable the maximum power point voltage to match the desired battery charging voltage includes but not limited to: judging whether the secondary battery can be charged according to the maximum power point voltage of each photovoltaic panel series branch as recorded in the latest unit time period; if YES, determining the target number of series-connected photovoltaic panels which are of the photovoltaic panel series branch and enable the maximum power point
S1, specifically, according to the battery charging demand voltage of the secondary battery, the current number of photovoltaic panels in series and the current maximum power point voltage of each photovoltaic panel series branch, the series connection of the photovoltaic panels is determined. The target number of photovoltaic panels in series of the branch and making the maximum power point voltage match the battery charging demand voltage, including but not limited to: based on the maximum power of each photovoltaic panel series branch recorded in the most recent unit period point voltage to determine whether the secondary battery can be charged; if so, based on the battery charging demand voltage of the secondary battery and the current number of photovoltaic panels in series and the current maximum power point of each photovoltaic panel series branch. Voltage, determine the target number of photovoltaic panels in series of the photovoltaic panel series branch and make the maximum power point voltage match the battery charging demand voltage, otherwise trigger the generation and display of a reminder message indicating that it is not currently rechargeable. Specifically, the most recent unit period may be, but is not limited to, the most recent 1 minute, the most recent 3 minutes, the most recent 10 minutes, etc. Since the maximum power point voltage of each photovoltaic panel series branch recorded in the latest unit period can reflect recent weather changes (such as ambi