In the era of renewable energy and technology available to the masses, gadgets such as solar chargers are a reality that can get us out of more than one trouble. Its main advantage is clearly obvious: the possibility of obtaining energy without depending on a plug or a portable charger.
In this Guide, you will learn everything you need to know to buy a portable solar charger: components, features, advantages and disadvantages compared to solar power banks…
No time to read? No problem! In the list below you can see the solar chargers we like the most on Amazon according to the criteria outlined in this guide:
If you have made it this far, congratulations reader! We can see that you are really interested in getting to know this practical gadget in depth.
- 1 What is a solar charger? How does it work?
- 2 How to choose a solar charger: key features
- 3 Solar Power bank vs Solar Charger: how long does it take to fully charge?⌚
- 4 Charging a cell phone using only solar energy 📱🌞
- 5 Best solar power banks (November 2022) 🚩
What is a solar charger? How does it work?
Basically, we could say that a solar charger works just like a cell phone charger with the difference that its energy is obtained from sunlight.
The solar charger is composed of one or more solar panels that are responsible for transforming sunlight into electrical energy to recharge instantly any other device with a USB charging port such as a cell phone, tablet, Bluetooth speaker, smartwatch…
Each solar panel is composed of photovoltaic cells, usually made of monocrystalline or polycrystalline silicon although we can also find models with panels made of CIGS.
One of the major limitations of these solar panels is the small amount of energy they produce per individual cell.
That is why it would be necessary to use large panels (which would be impractical for a portable solar charger) for this reason several small panels are connected in parallel and then deployed to capture more solar radiation.
Moreover, solar chargers do not store the energy produced in an internal battery but transfer it directly to the connected device. For this reason, we recommend 2 tips:
- Have a correct exposure of the sun’s rays on the charger panels so that the device is charged as fast as possible.
- Use a power bank as the main charging device to store the energy obtained and charge other devices at any other time of the day.
How to choose a solar charger: key features
There are many factors that can determine the buyer’s choice of one solar charger over another, let’s see which are the most important for us:
Solar charger power (W)
The power, measured in watts (W), that appears in the specifications of a solar charger indicates the capacity of its panels to produce energy from sunlight.
This power corresponds to the sum of all the solar panels that make up the charger, for example, this BigBlue model has 4 panels of 7W, then the total power is 28W (4 x 7W).
As a general rule, the more power the solar charger has, the more panels it will have, and therefore, the larger and heavier it will be.
However, one thing is the power that the solar charger is capable of generating and quite another thing is the power it supplies at its output ports:
Manufacturers usually limit the output power, i.e., the solar charger does not offer all the power that its panel (or set of panels) is capable of producing. This is done mainly for safety (to avoid excessive overheating) and to extend the life of the panel itself.
In addition, there will always be another power reduction depending on the conditions of use of the charger: angle of incidence of the sun’s rays, cloudy days, etc…
Output ports power
The output power at the charging ports of the solar charger determines the charging speed of the connected devices, i.e., the higher the power, the faster the devices will charge since the ports will have a greater capacity to meet the power demand of each connected device.
Let’s see an example comparing 2 models of the BigBlue brand that, in optimal light conditions, their solar panels can generate up to 28W:
|Model||Solar charger power||USB output ports power|
|B401D||28W||3x 5V/2.4A max, 5V/4.8A 24W|
|B401E||28W||2x 5V/2.4A max, 5V/4.0A 20W|
In this table we can see that each USB port can supply a maximum power of 12W (5V x 2.4A), then if we want to charge a single device that supports a current of up to 2.4 amps of current at 5 volts, we could use either of the 2 models.
But what if we want to charge another device at the same time at its maximum charging speed (5V-2.4A)?
In this case, the B401E model is limited to 20W between its 2 USB ports, unlike the B401D model which is able to provide the power demanded by each device.
Charging ports: USB and DC
Most solar chargers include USB output ports that can be used to charge any electronic device that charges through this type of port.
In general, it is a USB type-A that works at a voltage of 5 volts (standard charging) and supplies a maximum power between 10-12W.
Although there are also new models that incorporate the USB type-C port and even support Quick Charge (QC) or Power Delivery (PD) fast charging protocols being able to supply up to 24W and work with a voltage of 5, 9, and 12V.
The DC port is the other type of output port that we can find in higher-power solar chargers. It works with a voltage between 18-20V and is commonly used to charge a solar generator, a laptop, or a drone.
Solar panel efficiency
Efficiency is the ability of the charger’s panels to convert solar energy into electrical energy.
Assuming optimal lighting conditions and correct orientation of the charger to receive as much solar radiation as possible, solar panels have an efficiency between 21-24%.
This efficiency will depend on the quality and type of panel used by the manufacturer, we recommend brands that use panels with SunPower technology:
SunPower is a company specialized in the production of crystalline silicon panels that are characterized by their high quality, based on a silicon technology that was developed at Stanford University.
SunPower panels have been used in large solar power plants worldwide as well as in NASA projects, that is, what Amazon sellers seek to convey with this is that they are panels that guarantee quality and excellent performance.
Solar Power bank vs Solar Charger: how long does it take to fully charge?⌚
At first glance, you may think that a power bank with an integrated solar panel is cool because you can store solar energy in its internal battery and then use it to recharge your devices.
However, unlike a solar charger, the solar panel that incorporates a power bank is very small, which means that it would need to be exposed to the sun for many hours to fully charge its battery. This same problem occurs if you want to recharge a device.
We think a solar power bank should be used as a normal power bank and recharged by USB cable before traveling or hiking.
If you are looking to charge your devices directly with solar energy, use a solar charger! or a combination of both accessories to store the energy generated.
Next, let’s see a practical example of how long it would take to fully charge a power bank using its solar panel:
To do this, we have purchased the PN-W12 model of the Blavor brand, which has the following specifications:
- Solar panel output: 300mA/5V (25000 lux)
- Battery capacity: 20000mAh/3.7V
With this data, we know that the Blavor power bank’s solar panel can provide a current of 300 milli-amperes (mA) in optimal lighting conditions (25000 lux).
Theoretically, taking into account a voltage of 5V and in the best lighting conditions and incidence of solar rays, this panel could provide a maximum power of 1.5 watts (W):
Power bank Blavor solar panel power = 300mA x 5V = 1500mW / 1000 = 1.5W
On the other hand, this model has a 20000mAh battery capacity which allows it to store 74 watt-hours (Wh) of energy:
Stored energy Power bank Blavor = 20000mAh x 3.7V = 74000mWh / 1000 = 74 Wh
To recharge the power bank battery we can use the mains by connecting a charger to its micro USB or USB-C input port, or we can use its solar panel.
In our tests performed using the mains, we found that it is necessary to provide about 90 Wh of energy to fully recharge the power bank being the recharge time of 8 hours.
However, if we want to use the solar panel, we know that in ideal sunlight conditions it is capable of providing 1.5W of power, therefore, we would need 60 hours to provide the 90 Wh of energy needed to restore the 74 Wh of energy stored in the battery:
Solar recharge time = 90Wh / 1.5W = 60 hours
If we take into account 12 daytime hours (from 8 am to 8 pm) in optimal light conditions, we would need 5 days to fully recharge the power bank, using only the solar panel as a power source:
Solar recharge days = 60 hours / 12 hours/day = 5 days 😱
These calculated data are theoretical since ideal light conditions have been taken into account in which the solar panel always provides its maximum power (1.5W).
In addition, we would only be able to obtain 12 hours of sunlight in summer, being practically impossible to obtain in winter.
Logically, in practice, this is not the case, since the sun’s rays do not always strike at the same angle and do not always maintain the same intensity during the 12 hours of daylight that we have taken into account for the calculation.
In conclusion, in real conditions, the recharge time of the Blavor power bank through its solar panel will be much more than 5 days.
As we can see, the solar panel is not useful for fully recharging a power bank, but rather, it is designed to supply a small amount of energy in an emergency.
For example, in the case of running out of battery in our cell phone, it could perhaps provide enough energy to make a call.
Update: Power bank with multiple solar panels
There are new models, such as this one from Blavor, that include 5 foldable solar panels, thus increasing the area of exposure to the sun and reducing charging time. We have not yet performed a test, however, we still prefer a solar charger.
Charging a cell phone using only solar energy 📱🌞
In the following test, we are going to analyze the charging of the BQ Aquaris X2 Pro smartphone using as a power source only solar energy obtained for 7 hours by means of:
- A power bank with an integrated 1.5W solar panel (Blavor PN-W12).
- A 16W solar charger with 3 panels (RAVPower RP-PC008).
Charging test with solar power bank
First of all, the battery of the Blavor power bank has been completely discharged since we have mentioned that the smartphone charging is going to be done only with solar energy.
Then the Blavor power bank was exposed to intense sunlight for 7 hours.
In addition, during this time, it has been rotating on itself (simulating the rotational motion of the Earth) so that the sun’s rays hit it as directly as possible, trying to do so perpendicularly to the solar panel of the power bank.
After 7 hours, we performed a complete discharge of the power bank battery using a 10W electronic load (5V/2A) to see the energy (Wh) it is able to provide.
This whole process has been monitored on a PC using a USB multimeter:
As we can see in the graph, we have obtained 4.56 Wh of energy for a constant discharge at 10W (5V/2A).
To get an idea, the BQ Aquaris X2 Pro smartphone needs to be supplied with approximately 15 Wh of energy for a full recharge (100%) of its battery (~12 Wh).
Therefore, with 7 hours of exposure to the sun, the Blavor power bank could recharge up to 30% of its battery:
Number of charges = Useful solar power bank energy / Smartphone recharge energy = 4.56 Wh / 15 Wh = 0.3
Charging test with solar charger
For this test, we are going to store the energy obtained by the RAVPower solar charger in a power bank and then use that energy to know how many times we can recharge our BQ smartphone.
In our case, we have used the Blavor power bank (obviously covering its solar panel) although you can use any other power bank.
As in the previous test, the panels of the RAVPower charger were exposed to the sun for 7 hours with the power bank connected.
Afterwards, the power bank was fully discharged at 5V/2A (10W) to see how much power it is capable of supplying:
In this case, the graph shows us that 43.57 Wh at 5V/2A is the total energy supplied.
Then, with 7 hours of sun exposure, RAVPower solar charger could fully recharge almost 3 times the battery of BQ smartphone:
Number of charges = Useful solar charger energy / Smartphone recharge energy = 43.57 Wh / 15 Wh = 2.9
In this comparison, we clearly see what we said in the previous section:
This type of power banks with integrated solar panel are useful to save us from a hurry as they supply a small amount of energy to use in an emergency but they are not useful to recharge them exclusively with their solar panel.
If we do not have access to the mains and we need to recharge our power bank using only solar energy, it is best to use a normal power bank (without solar panel) powered by a solar charger (suitable for the power demanded by our power bank).
Best solar power banks (November 2022) 🚩
Although we prefer to use a portable solar charger, in the following list you can see the solar power banks with the most interesting specifications that you can buy on Amazon: