Solar panels 12 V for charging the car battery
Let’s find out what kind of panels you need to pick up to be able to charge a passenger car battery. Let’s take a battery with a capacity of 60 Ah, voltage 12.6. 6 cans connected in series with V = 2.1 V. Charging current is 0.1 60 = 6A. Charging time up to 12 hours. This charge can be provided by a 60W panel with a controller fitted. Battery with dimensions of 1m2 gives 15W at 12V.
So far there are no solar panel options to fully charge a car battery. It is possible to recharge the battery and partially power the onboard network. However, folding designs have emerged that can be spread out at a camping or resting spot. Panel batteries can be installed in a country house. They will gently power a car for twenty-four hours during a long parking period.
There are solar battery chargers created by the British company Ring Automotive Ltd. Manufacturer offers the RSP type, 1,5W; 2,4W; 4,8W. The devices have suction cups, crocodiles, a 2.7 m cable, and are used to recharge while parked in the sun for several days. A solar panel from this manufacturer to charge a car battery is available for 100.
Developments of Ukrainian engineers from “Kvazar” enterprise are considered to be the best so far. They have developed several models of collapsible panels. The device provides power of 90W, charging current up to 7A. Total weight of the construction is 8 kg, the price is 400.
Charging the batteries with solar panels
Nickel cadmium batteries (NCA) are often used to provide operation from radio expeditions. But, with the time of work on the air NSA must be recharged. In the conditions of expeditionary work one of the best options for recharging the batteries is the use of solar panels. The sun’s energy will do the job of recharging the batteries quite well. Let’s see how to use solar panels to charge the batteries.
Type of solar battery
The most common in the CIS countries are solar panels of the type BSK-1, BSK-2, Elektronika MCh/1. These batteries are or were formerly produced by many electronics factories. Sometimes you can also find on sale imported, mostly Chinese and Korean solar cells, with parameters comparable to the batteries types BSK-1, BSK-2, Electronics MF/1.
These solar cells can provide a charging current to the battery in the range of 35-50 milliamps, no more. And it will be with good sunshine. Consequently, with widespread solar panels can provide charging low-power batteries with a capacity of no more than 0.45 A / h. Note that the widespread type CNK-0.45 batteries have just such a capacity.
It is also necessary to take into account that in the midsummer, in July, the light period in which the battery effectively give energy, usually lasts no more than 7-9 hours. The most efficient time to work the solar panel from 10 to 17 hours. After this time, the current of the solar cells drops. The current generated by the solar panel in cloudy weather drops. Some orientation of the solar cells with respect to the position of the sun, helps to increase the current they generate, but Try spinning the batteries yourself in search of the best light, and see that it’s not an easy task.
So what can be done to increase the current generated by the solar panel? The easiest way to increase the current of solar cells is to connect them in parallel. Of course you must connect the solar cells with the same number of cells and therefore provide the same photovoltage and photovoltage. But still parallel connection of solar cells, as shown in Fig. 1, not desirable. The best results are obtained when solar cells are connected in parallel, as shown in Fig. 2.
Figure 1 Unwanted solar panels Figure 2 Parallel solar cells
Let’s look at why the parallel connection of solar cells shown in Fig. 1.
Due to the different illumination of the solar cells, the voltages they generate will be slightly different from each other. As a consequence, only one solar panel will work effectively. When you connect the solar cells in the circuit shown in Fig. 2, the voltages they generate are more evenly distributed across the solar array. As a consequence, partial shading of some of the cells will not do much damage to the solar cell operation. However, the parallel connection will require unsoldering the finished batteries and then reconnecting their cells to each other. The work is quite tedious, a grass scythe of wires between the batteries But if a large current is needed, this work will still have to be done.
To increase the voltage of the solar panel, you can connect as many solar cells in series as you want. The voltage of such a solar cell will be equal to the sum of the voltages of all of its constituent solar cells. The current given off by this battery will be limited by the current of the worst cell.
The most important disadvantage of solar cells, in my opinion, is only their relative high cost. But this drawback pays off for the effective operation of solar-charged batteries.
Charging a Car Battery with a Solar Panel and Charge Controller
Charging / recharging batteries
So, with enough solar cells you can create a solar panel with virtually any voltage and current, and capable of charging any type of batteries. It’s just the cost of such a solar panel. Of course, we should not forget that a powerful solar cell will occupy a large area for its installation. It should also be noted, if the full sunlight of the battery is a limited time of day, it is desirable to use a solar battery, which provides accelerated charging current, the value of which is in the range of 0.15-0.3 of the capacity of batteries.
Usually in radio expeditions effective work is possible in the evening and at night. During this time, the transmission on many bands is improved, there are many local stations. The use of the solar battery allows the batteries to be discharged in the evening and at night during the broadcasting operation, and to be recharged during the day.
If the solar panel provides less than the nominal charging current, less than 0.08 of the batteries’ capacity, then it is not charging, but only recharging the batteries. This means that during daylight hours the solar panel must be permanently connected to the battery, all the while constantly recharging it. At the same time it is necessary to control that during the operation of the battery the voltage on one of the cells would not be lower than 1,2-1,15 volt. When the voltage is below 1.15 volts, the battery must be removed from service and placed on charge. Otherwise, the cell voltage will drop to 1.1 volts in a short time, and such a discharged battery pack will be impossible to use on an expedition without serious recharging. This indicates that on the expedition, it is necessarily necessary to monitor the voltage of the battery under load. The discharge and charging characteristic of a single battery is shown in Fig. 3.
Figure 3 Discharge and Charging Characteristics of a Nickel/Cadmium Battery
To further understand the process of charging the solar battery, consider the characteristics of the solar cell. The dependence of the current of one cell of the solar battery type BSK-2 on the voltage on it is shown in Fig. 4. This graph is taken at optimal illumination of the solar cell. This graph is also typical for other solar cells. Of course, the value of the maximum current will depend on the power of the solar cell. To take this graph a variable resistor is connected to the illuminated solar cell. Change the resistance of the variable resistor, and measure the current flowing into the resistor and the voltage on the solar cell. A schematic for taking a volt/ampere characteristic of a solar cell is shown in Fig. 5.
Figure 4 Volt/ampere characteristic of the solar cell Figure 5 Schematic diagram for volt/ampere characteristic of the solar cell
When the solar cell is operating without a load, the photovoltage EMF on the cell will be about 0.6 volts. When the load is connected and then the load resistance decreases, the current in the load will begin to increase. the load voltage will then begin to decrease. A voltage of approximately 0.45 volts on the load is the optimum mode of operation for the solar cell. As you try to increase the current draw, the voltage on the solar cell drops, and the current it generates continues to remain virtually unchanged. This suggests that the solar cell is an almost ideal source of current, just what is needed to charge the batteries!
For the solar cell current measurement circuit (see Fig. Fig. 5) the graph of power dissipation in the load resistance of the solar cell was plotted. The graph is shown in Fig. 6. This graph was taken at optimum illumination of the solar cell. To construct the graph, the load resistance of the solar cell at various voltages was measured. Then, based on the value of the load resistance, and the current flowing through the load, a graph of the power dissipated in the load was plotted. This graph shows that the maximum power returned to the load by the solar cell will be at a load voltage of 0.45 volt. The optimum load voltage (0.45 volts) differs from the photo EMF voltage (oh.6 volts) by a factor of 0.75.
Fig. 6 Power dissipation in the load resistance as a function of the load voltage
Consequently, to charge the batteries, you can use a solar panel that has a maximum generated current approximately equal to the charging current of the batteries. In this case, the solar battery will automatically charge the batteries with the necessary charging current at its illumination. The battery must be connected to the accumulators through a diode, as shown in Fig. 7. This is necessary because in unfavorable sunlight, the voltage on the solar panel may drop below the voltage of the batteries being charged. In this case the accumulators, instead of their charge, will be discharged through the internal resistance of the solar battery. Buffer capacitor C1 is needed if, the batteries will be used to work during their charging/recharging.
Figure 7 Connecting the solar panel to the batteries
A milliammeter is included in series with the solar cell. Including a milli-ammeter is highly desirable. It shows how much current the battery draws from the solar panel. And this makes it possible to judge whether the battery is under charging current or training current, and generally whether the solar battery is working at the moment or not. It is convenient to use a record indicator from an old tape recorder as a milliammeter.
A shunt for this recorder is also easy enough to make. On the resistor type MLT-0,5 we wind 1 meter of wire type PEL-0,1. Connect the shunt in parallel with the microammeter and measure the maximum current it can measure. Let’s assume that it is 100 milliamps. And to charge the batteries a solar panel with a maximum current of 40 milliamps is used. Consequently, it is convenient to have a maximum scale of 50 milliamps. In order to obtain this maximum current deflection of the microammeter, the shunt resistance must be increased by a factor of two. To do this you need to increase the shunt wire length to two meters. Similarly, a practical shunt adjustment can be made for other milliampere deflection currents.
Under camping conditions, the charging process can be considered complete when the voltage across the cells under load is at least 1.25 V/cell and their EMF is at least 1.36 V/cell. If the solar battery is used only for charging the accumulators, then it must be recharged as necessary. as the batteries are discharged. Under unfavorable conditions, recharging can even last the whole day of light. At night, the solar cells do not need to be disconnected from the batteries because they will be turned off automatically by the diode VD1 (see Fig. Fig. 7).
Calculation of the solar panel parameters
Here is an example of how to calculate the solar panel needed to charge the batteries. As shown in the graphs in Fig. 3, while charging the battery, the battery voltage would be within 1.4 volts. To power the equipment in the field, a supply voltage of 12 volts is usually used. Such voltage can be provided by 10 nickel cadmium batteries connected in series. To charge a battery of 10 nickel cadmium batteries in series, you need to provide them with a voltage equal to 14 volts (101.4 = 14). At the maximum efficiency of the solar panel, when the voltage of one solar cell is 0.45 volts, a voltage of 14 volts can provide a solar panel consisting of 31 cells (14/0.45=31).
Consider the voltage drop across the diode, which is 0.7 volts. Consequently, the solar battery must have two extra cells. The total number of solar cells in the battery in this case would be 33 (312=33). Voltage photo EMF solar battery containing 33 cells will be 19.8 volts. So we come to an important thing. It turns out that to charge a 12 volt battery, you need a solar panel with a photo EMF of almost 20 volts! Such a battery can be assembled independently using individual solar cells or a few prefabricated solar cells.
In the passport of the solar panels indicate just the voltage of the photo EMF. On sale there are solar cells with voltages of photo EMF equal to 12 and 9 volts. Consequently, at the optimum load impedance (see Fig. Figure. 6) voltage on these cells is 6.75 volts for 9 volt solar cells, 9 volts for 12 volt solar cells.
Two solar cells in series with 9 and 12 volt photo emf voltage can be successfully used to charge a 12 volt battery. Exceeding the total voltage, which for two batteries will be 21 volts, calculated voltage of 20 volts to one volt is not terrible. This excess will be compensated by some decrease in the output voltage of the solar cell, which will occur due to the uneven illumination of the cells that make up the solar cell. Of course, solar panels must not current more than the batteries’ charging current.
Two 9 volt solar cells in series will not fully recharge the battery. They will only recharge it to no more than 20% of its required charge. fig. 3). However, a solar panel connected to a 12 volt battery with a photo EMF of 18 volts will help “unload” the mode of operation of this battery. It will be able to smooth the peak current loads and provide rechargeable batteries to the best of its ability.
Operation of solar panels
When using solar panels, care should be taken to ensure that they are placed in as much light as possible and that they are equally illuminated. precautions should be taken to prevent mechanical damage to the batteries and their direct exposure to humidity and dust. Shaking of the solar cells must be avoided during transportation.
It is necessary to follow the temperature rating of solar cells, which is listed in their passport. Usually it’s.40° 50° С. In summer, in hot weather, solar cells should be placed on a surface that is not subject to much heat, such as a piece of white cloth or shiny aluminum foil. They get very little heat and the solar panel on top of them will work satisfactorily.
It should be noted that nickel cadmium batteries also do not work well at high and low temperatures. Battery temperatures fall below 0° C, resulting in a significant drop in capacity.
Solar panel test results
Practical tests of solar panels in conjunction with batteries have shown greater efficiency of such joint work.
In practice, I have used several sets of solar panels. One set provided 18 volt photo EMF voltage. It was made up of two 9 volt solar cells. Later I managed to buy a 12 volt solar battery. As a result, it became possible to use a set of solar panels with a voltage of 21 volts. These solar cells provided a load current of up to 40 milliamps.
The first experiments were conducted in conjunction with a solar panel with a voltage of 18 volts photovoltage. The solar panel was permanently connected to the batteries according to the scheme shown in Fig. 7. The solar panel at 18 volts provided successful recharging of the battery using cells CNK-0.45 and 1.5-NKGN. Unfortunately only for recharging. Intensely discharged during night work, the batteries were no longer able to be recharged by such a solar panel. As a result of this, the next night the batteries worked for a short time.
However, with small load currents of these batteries, such a solar panel was quite useful. During the light period it provided a constant recharging of accumulators, kept them under the training current, which had a favorable effect on the operation of accumulators. As a result, the batteries together with the solar panel lasted much longer than without it.
But the picture was different when using a 21 volt solar panel, which was made up of a 9 volt and a 12 volt battery. This solar cell made it possible to charge the batteries during daylight hours. And this charge was quite enough for intensive evening work of the transceiver with power of 1 watt. Of course, such a solar battery is optimum only for charging a TsNK-0.45 type battery, which has a charging current of 45 mA. Batteries of the 1.5 NKGN type, having a charging current of 150 mA, such a battery couldn’t charge fully. But at the same time it will add significantly to the wasted capacity during the dark period of operation!
a 21 volt battery may be connected to 1.5 NKGN type batteries operating in daytime. it is undesirable to connect it to accumulators of CNK-0,45 type, working together with radio equipment. In this case, this type of battery will work hard for them, which may cause their accelerated failure. To avoid this it is desirable to use two storage batteries in expedition, one for work and another at the same time to charge.
Warning: overcharge is possible!
It is necessary to pay attention of radio amateur that in some cases the solar battery can overcharge the battery. And this will lead to polarity reversal of the battery cells and its failure. We can immediately say that when using the 18 volt solar battery, you can not be afraid of overcharging the 12 volt battery. As we have already reviewed, the solar cell at 18 volts will only be able to recharge the battery at 20% of its nominal capacity. After that the solar panel will only provide a training current for these accumulators.
It is a completely different case when using a solar panel at 21 volts. This battery is capable of providing charging current even after the batteries are fully charged. It should be noted at once that when using a solar battery providing a charging current of 40 milliamps, you can ruin only batteries type CNK-0.45. Batteries of the 1.5-NKGH type, which require a charging current of 150 milliamps with such a solar battery during the expedition is difficult to ruin. But you still need to be careful when charging them.
In order not to spoil the battery, it is necessary to record the time of its operation. After that, carry out the additional charging of the given capacity. Here is an example of this calculation. Let’s take the simplest case. A rechargeable battery made up of CNK-0.45 cells (therefore, with a charging current of 40 milliamps) powers the receiver with a consumption current of 40 milliamps. Suppose this receiver ran for 4 hours in the evening. Consequently, the lost capacity of the battery is equal to 160mA/hour (404=160). In order to restore the lost capacity of the battery pack, it would need to be charged 150% more than the lost capacity. Consequently, this battery must be under a charging current of 40 milliamps for 6 hours ( 160/40=4; 41.5=6) during the day to restore the charge.
And if the battery pack was used to power a transceiver which is working in transmissions? Well, we need to consider the time during which it works for transmitting. Suppose the transceiver consumes 50 milliamps during reception and 150 milliamps during transmission. Worked the transceiver for 3 hours, of which half an hour to transmit. Consequently, the battery 2.5 hours gave a current of 50 milliamps and 0.5 hours of 150 milliamps. Let’s calculate the lost capacity:
To restore the lost capacity of the battery, it must receive a charge of 150% more than the lost charge. Consequently, this battery must be at a charging current of 40 milliamps for 7.5 hours ( 200/40=5; 51.5=7.5) during the day to regain a charge.
Eliminating the memory effect
Unfortunately, nickel cadmium batteries have what is called a memory effect. How this manifests itself? If the battery is discharged several times without fully discharging, say, 30% of its capacity, and then recharging it again, the battery will “remember” the discharge cycle. Subsequently, the battery will only give up 30% of its charge even if it receives a full charge. Usually in radio expeditions the batteries do not have time to catch this disease. The battery experiences different discharge/recharge cycles each day, and the discharge cycles can be quite deep. However, after finishing the expedition in which the rechargeable batteries were used, in order to eliminate the memory effect, the battery should be given at least two cycles of full discharge/recharge.
Charging Rules
Car batteries are charged in a relatively gentle mode, in which the current intensity does not exceed 0.1 of the nominal capacity. For example, with a battery capacity of 60 Ah the charging current should not exceed 6 Ah, otherwise the battery will slowly deteriorate.
In this respect, charging a car battery from a solar panel is quite a good option, since most types of light-sensitive panels at the output does not have a current of more than 1 A. Such devices are usually used to maintain the condition of the battery. Their power is 5-6 watts. If you need a full charge, you should use more powerful models capable of 30 to 60 watts. Most often used in the following situations:
- recharging a dead battery;
- Maintaining the battery charge level while driving a long distance with the air conditioner, radio or stereo running, etc.д.;
- recharging of the battery in case of necessity of prolonged idle time of the vehicle (e.g. for the time of the owner’s departure).
For normal charging of the car battery is recommended to use a solar charger for 12 V car battery with a length of at least 1 m. They develop about 15 W of power, at a voltage of 12 V, respectively.
It is important that the charger kit includes a charge controller. If you don’t have one, you should buy one and connect it to the charger. This will avoid overcharging or reverse discharge of the battery, which adversely affect the condition of the battery plates. If possible, it is recommended to use a chain of several solar panels, distributing them in the most convenient way to receive the sun’s rays.
Charging rules
Every car enthusiast knows that you do not need to rush the time when you charge your battery. The current capacity for lead-acid batteries should not exceed 10-12% of their capacity.
In other words, if a good battery with a capacity of 60 A/hr is completely discharged, the current value when charging should not exceed 5-6 A. Charging time under these conditions will be 10-12 hours. If you exceed these figures, there is a risk of damaging the car battery.
With solar panels you can not worry, because the maximum current in them is not more than 1-2 A. The battery with a capacity of 40 A/hr will charge slowly, but will not fail.
A solar solar system up to 7 watts is only able to support the battery, for a full charge a panel of 50-70 watts is needed. However, for this scheme, you need to buy a controller, which will monitor the power and will not allow to ruin the battery.
In practice one solar panel with 40W power and 20V voltage is able to charge a battery with a capacity of 50Ah to 40-50% in 7-9 hours.
Read an article about how to make a solar panel with your own hands here.
Makeshift solar car battery charging
This article describes the charging from the solar cells, its features and how easy to make it yourself without much cost, various ways.
It often happens when you go to the nature with overnight stay, by morning the battery is already sitting. The battery is constantly losing its power, both while driving and when parked, the work of the receiver, air conditioner, DVR, all consuming a charge. For such cases, there are solar panels for charging (12 W), they come in different shapes, sizes and functions. But, unfortunately, they only work on a sunny day.
The specifics of charging depend on:
Choice of solar charger
Choose a solar charger based on the following arguments:
- The amount of energy generated depends on the area of the storage area, so the larger the parameters of the area, the greater the amount of energy stored.
- Technical indicators also have a significant impact on the choice of device. In order to be carried out one hundred percent charge, you need to ensure the accumulation of charges for several days. The use of solar panels will be beneficial if they maintain the charge throughout the journey of the vehicle, especially when the radio, air conditioning and other technical means.
- If you take a long break from using your car. For example, when you leave your car in the garage for a while, you do not have to worry that the battery will run out quickly. Solar charging will keep your car running during the owner’s absence.
Based on the above conditions to provide an uninterrupted power source, the ideal solution would be to choose this device to accumulate a charge of electricity.
The condition of the car battery is a subject of constant attention and care of motorists. A device that is not discharged on time will cause a lot of trouble even in the city, and if this happens away from busy highways, the problem will prove to be quite complicated. A good solution to the problem is to use a solar panel to charge the car battery, which gives the opportunity to “revive” the dead battery without the involvement of outside help.
Car battery gives out stored energy all the time, both while driving and when parked. Operation of different devices. receiver, CD changer, car-recorder, refrigerator, air conditioner and other installations requires an increased consumption of battery energy. It is not uncommon for a car owner to leave a radio or other device on in a hurry, and when he returns to the car, he discovers a hopelessly dead battery. It is good, if there is source of “light”, but such fortune is not always.
For such cases there are solar panels for charging the 12 volt car battery. They have different parameters, sizes and features. Specificity of such devices is in the ability to work effectively only on a sunny day. The source of solar energy is truly inexhaustible, but the capabilities of modern technology allow a limited amount of energy to be obtained from it. The performance of the device is directly dependent on the area of the working surface of the solar panel.
Thus, the features of charging a car battery from a solar panel are:
In addition, the technology and quality of production, the country and the firm-manufacturer and other usual factors that apply to any equipment affect the work of the set.
Solar 12v car battery chargers, like solar panels for campers, require the sun and a well-chosen position in which the light flux falls perpendicular to the entire surface of the light-sensitive cells to work properly. When the panels are large enough to get the most out of charging, the placement of the device becomes a noticeable problem.
If we are talking about parking, especially in the field, the issue is solved quite simply. However, when you need to recharge while driving, the solar panel in the car to charge the battery becomes quite a challenge, a solution which is partly offered by the manufacturers of installations. They make special stands that allow you to place the panel in a convenient position for receiving the sun’s rays.
Solar charger for the car battery is inserted into a special socket on the boom, which has the possibility of fixation at a certain angle to the horizon. By turning to the sun and selecting the optimal tilt the working surface receives the light flux of maximum strength.
Unfortunately, such support structures are most often attached to low-power devices. The more productive panels have a larger area when deployed, and manufacturers allow car owners to decide on the optimal placement of installations.
The two options are considered the most convenient:
Both options have their advantages and disadvantages, so we should talk about them specifically.
Car roof
The outside surface of the sunroof has a large enough area to be constantly exposed to the sun’s rays. This makes it possible to place a solar panel with a total area of 1 m 2. and even more, which gives enough energy to fully charge the car battery even after a deep discharge. Solar battery charger for 12 v car battery, which has enough power for this in 30-60 watts, you need exactly the same area.
The disadvantage of this option is the need to somehow fix the panels on the roof, because they are relatively lightweight and can be moved or dropped by a normal gust of wind. When driving, the problem increases many times over, as the oncoming air flow creates significant pressure and can tear the panels off. While driving, there is a risk of not noticing it immediately, forcing you to turn around and go looking for it.
The upper plane of the dashboard is convenient to place a solar panel of suitable size. The device is located inside the cabin, which protects it from the weather or the encroachment of unclean hands.
An additional convenience is the ability to connect to the cigarette lighter or appropriate terminals, which is much more convenient than when installing the panels on the roof, when there is little problem with the wires. It is possible to charge the battery both while parked and while driving without taking additional measures to reinforce the fixation of the device.
The disadvantage is the limited area of the panel, which does not allow to fully charge the battery. A conventional solar panel to charge the car battery needs a larger area, and only an additional panel can be installed on the dashboard, recharging the battery to a certain level.
Another disadvantage is the ability to get effective solar flux only in a certain direction of travel or positioning of the car while parked. If the direction of travel does not coincide with the position of the sun, the effectiveness of the panels drops dramatically. Despite manufacturers’ claims of being able to work in cloudy weather, the device noticeably loses performance when access to direct light is restricted.
Solar panel for recharging car batteries
Solar cells are widespread today and have penetrated into almost all spheres of human activity, successfully being used as a highly efficient energy-saving technology. Major automobile concerns have begun to equip their car models with photomodules, which have endowed them with even greater energy autonomy.
But even so, using solar panels to charge the car battery is a technical novelty for many car enthusiasts. Most of them believe that the installation and use of such equipment is quite difficult. This is not true at all.
Most home solar systems use automotive batteries. Currently, there are many manufacturers offering different modifications of solar panels at various prices. This will allow you to buy without much difficulty the most suitable option in terms of voltage and power. An excellent example would be a solar panel, manufactured by SunForse.
Solar battery for battery charging SunForse
The device offered by the mentioned company, a large and productive solar panel. The manufacturer claims 15W power and 1A current. This device is designed to charge a 12-volt battery. The model of this device copes with its work perfectly even in bad weather conditions. The operating range of the device.37-80.
TCM-15F solar battery charger
It is impossible not to mention another worthy variant of the device, which is based on a flexible basis. TCM-15F. This device was originally conceived to do the work of an energy source. However, due to its technical characteristics, the device can also be used as a battery. Dimensions are much smaller compared to the above model and are 60×25.5х0.15 cm. The manufacturer’s declared capacity is 15W, output current is 1A. Unit TCM-15F, made on flexible base, so it is easy and safe to fix it on the roof. The SunPower photovoltaic cells used here have an efficiency of up to 20%. This charger is enough to power a compact media player such as the Tronsmart MXIII Plus.
Irreplaceability of solar panels for vehicles
The vast majority of motorists are familiar with the problem of a dead car battery. Capturing at the most inopportune moment. The reasons for this can be very different: listening to music for a long time, forgetting to turn off the headlights, the car was in the frost for a long time and other. In such a situation will be just an indispensable device that can give a sufficient charge to the battery.
Where best to place the solar panel
The most suitable place to place a solar panel is on the roof of the vehicle. For fast and efficient charging requires photomodule with dimensions of 1m2. In sunny regions several such modules are placed on the roof of cars, thus creating a small power plant. And as it was found in the course of studies, under favorable climatic conditions, you can even completely abandon the electric generator. The solar cells increase battery efficiency and save fuel.
The size and model of the solar panel depends on its future purpose. For the small needs of radios and other low-power devices a small photovoltaic panel is quite sufficient. However, if there is a need for energy of greater capacity, you should find out exactly what model of solar panel you need to buy.
It is not necessary to use the roof of the car to place the photomodules. There are a lot of folding models of devices, which will be convenient to carry in the trunk. It is also possible to charge the battery on the solar panels through several portable modules.
For the reanimation of the battery will be sufficient solar panel at 5-6 W. So in the case of full and fast charging will require a whole complex, the power of which should be 30-60 watts. But in most cases a module with a power of about 15 watts and the size of 1 m in length is used.
Of course, if this roof of the minibus, it is quite rational to place not one, but several photomodules, which forms a device that can provide the car with a constant current. Solar batteries for car battery charging will be quite actual for every motorist.
Installation on the rear window of the car Ravon R4
At the time the idea was born, I could not find any information about the effectiveness of solar cells under the windows of cars. The fact that the cobalt glass shows 70% light transmission did not add optimism. I specifically chose a panel that was not quite small as in the calculators, but also gave the necessary minimum, taking into account all the disadvantages of installation inside the car and in the whole use case. It is not always possible to park the car back to the south without shade, and the glass tends to get dirty.
As a result, after two days of operation of the test setup I can conclude that I didn’t make a mistake with the choice of dimensions. Probably even should have looked for a wider model, for measurement is measuring, but in real life on the window was a lot of free space. Or take one of these, parallel them and place it on the edge of the glass, leaving the view in the middle.
It was difficult to measure without a multimeter, so I connected my Vympel-37 charger and used it as a voltmeter. Fortunately, it has a measuring range of input voltage from 8 to 23 volts. To tell the truth it was not convenient to carry such a junk, that is why there are only such photos:
I managed to get a maximum of 16.9 volts, but in the reviews of the lot were pictures and with 21v no-load voltage, so there is no point in this test and go already clamp the panel to the glass.
This is a very exciting moment for it could happen so, that through the glass panel would give out less voltage, than it is necessary to charge the battery. But this did not happen, and even through the car’s rear window, which was covered with dirt on both sides, the red LED on the panel glowed, and there was even a small current on the USB ports of the built-in DC-DC converter.
Let’s connect the pins of voltmeter to the panel glued to the glass and get very good values for us. 16.9 volts under a clear sky and a relatively correct angle of the panel to the sun:
With the pre-functionality solved, and not having at the time of installation multimeter, the only way to check the presence of any current is to connect the controller to the car battery.
Yes, many will say that low-power panel can be connected directly to the battery through diodes and they will be right in their own way. It is likely that even at 18-21V no-load voltages on the panels when connected to the battery will give normal
13V on the terminals. But my case of using the set means dismantle from the car to a camping on vacation, and there will turn out to be quite useful the function of the discharge limitation of the battery at the lower threshold. Well and PWM controller has such feature as pulse charging, some “experts” have expressed the opinion that in this application the effect of acid-lead battery desulfation is achieved. As a result, I see no problem to connect all this goodness through the controller just in case.
Consumption of the controller at night, without solar power is 7.5mA:
Consumption of the whole car in standby mode with the controller connected is floating around 50-60mA:
As you can see the current consumption of the controller is small and the daily charge from the sun more than covers the consumption not only of the controller, but also all the consumers on duty, such as GSM-system, remote central locking or OBD-scanner. But let’s not get ahead of ourselves and let’s get back to the controller mounting.
At the moment, not fully examining the effectiveness of this entire installation, I will not make major installation.
We start by washing the inside of the rear window. Degrease the suction cup mounting area, heat it up and mount our solar panel:
At first I checked the working capacity of the controller by connecting it to the cigarette lighter. As a test version will go, but on Chevrolet Cobalt and Ravon R4 voltage at the cigarette lighter present only at the corresponding position of the key in the ignition and after 10 minutes. It can be fixed, in one of my articles I told about installation of jumper in cabin relay. But we do not have that much power of solar energy to waste it on all sorts of constantly powered DVRs, car stereos and chargers for mobile devices. And that means we need to look for where to get in our car constant 12v directly from the battery.
Bearing in mind the possible timing of the installation, I did not bury myself with the connection point and hooked up to the terminal in the fuse box. I have also connected my self-wired alarm Starline and for almost two years no problems with it appeared.
Don’t beat yourself up for the terminal block a la Wago and don’t wish a quick fire on my car 🙂 Just a reminder that all of this is VRE-MEN-NO, here.
Minus was taken there from some bolt on the body. In the photo above you can see both points of connection.
Next, we run the wire to the rear shelf. The good idea is to do it through the left sill, but experience in the past opened it to install the rear camera has shown that the latches tend to break. And so we go for the dumbest option and just throw the wire around the cabin. If after a while the whole installation justifies itself, I will redo it properly.
We are asked to install the controller on the back side of the shelf on the metal body reinforcements, but now the controller requires periodic attention during testing, so we leave it in a prominent place.
It remains only to observe the correct sequence of connecting the controller. Let’s turn to one of the many translations in Russian:
We are interested in connection of controller. Literally at every step they say about the need to connect the battery first, then the solar panel, and only then the load (if necessary). Not being a connoisseur of circuitry, I can not say anything about this requirement. It is possible that this is due to the ability of the controller to work with two voltages. 12 and 24, and therefore it must first determine what type of battery is connected to it.
In turn, I can say that I had the carelessness of missing the connection of the controller to the battery and for an hour, the connection was only the solar panel to the controller. At first glance did not find any damage or abnormalities in operation.
Connect the battery, make sure that its icon and the voltage on the controller lights up. Further we connect a solar panel (actually it is possible any power source, but there are nuances). If its voltage prevails over the battery, the solar panel icon will light up and if the battery voltage does not exceed the upper limit specified in the settings, the charging process will be displayed with a flashing arrow.
Regarding the view in the rear view mirror:
I can’t say, that the review suffered somehow. If you particularly want you can move the panel to either side, but I prefer the symmetry of convenience 🙂 After the picture, I just moved it as close to the duplicate stop light as possible and turned the connector to the bottom to make hidden wiring later.
I don’t use the rest two pins for load connection, they are useful only for camping installation. I will connect necessary consumers from it for voltage control at unloading. But a serious load on the type of inverters 12v-220v connect only directly to the terminals of the battery.
USB-ports on the controller are switched by the load mode. That’s why I checked if the consumption of the controller increases when it does so (on the display the icon of the lamp on the right side lights up). No, the current was the same. within 8mA regardless of load mode. So we don’t really bother and ignore his condition.
