A solar charger is a type of charger made up of one or more solar panels that transform sunlight into electricity to instantly recharge a smartphone or any other device with a USB port, such as a tablet, a Bluetooth speaker, a smartwatch, etc.

I could say that a solar charger works like a smartphone charger, with the difference that its energy comes from sunlight. Furthermore, solar chargers do not store energy on an external battery – just a few specific ones- but directly transfer the energy from its panels to the connected device.

For this reason, I recommend using it in conjunction with a power bank so you’re prepared for a cloudy or rainy day while still being able to charge your devices.

Components of a solar charger

Even if the variety of chargers is vast, almost all of them have many elements in common that are essential:

Solar Panel or Photovoltaic module

They are the main piece of this type of battery charger, making them stand out from the conventional ones; later, you will see the existing types and their differences.

Outgoing Ports

In addition to the conventional USB ports used to recharge almost any 5V device, we can also find ourselves in more powerful chargers with the new and multipurpose USB-C or the DC port, the port for recharging laptops.

Textile Material

Most solar chargers are made or covered with a waterproof textile that can withstand extreme temperatures, and this is because it is designed to work even in bad weather.

Most of these solar chargers usually include a small pocket, some with a zipper, where the USB charging ports are located and which allow us to deposit the device while it is recharging, protecting it, in turn, from direct exposure to the sun’s rays.

They also have metal eyelets and snap hooks to hold the magazine to the back of a backpack or any other place where we want it to remain fixed: tree, camping tent, umbrella.

Types of photovoltaic panels

When buying a solar charger, one of the characteristics to take into consideration is the type of photovoltaic panel that the charger has because it affects durability, performance, efficiency, and, obviously, the price:

CIGS

CIGS is the acronym of Copper, Indium, Gallium, and Selenide or Rame Indio Gallio Selenio; it is a type of solar panel that stands out for its flexibility and lightness, making it ideal for outdoors. They adapt very well to different types of surfaces, for example, a rock.

Its performance, it can be said, is quite good, even achieving slightly better results in cloudy conditions than monocrystalline and polycrystalline.

However, its major problem is durability because it degrades faster over time than mono/polycrystalline. Moreover, they are not always easy to place in front of the sun so that it recharges in the best possible way (later, you will know the importance of the angle at which the panel must be placed when recharging).

Monocrystalline

Dark in color, tending towards black, they are panels which, as their name indicates, are composed of a single crystalline silicon crystal; this panel type allows it to be much more “pure” than its main competitor, the polycrystalline.

This “purity” has a direct consequence on the performance of the panels because its efficiency (around 22%) is higher than that of polycrystalline panels (around 18%), thanks to the fact that the electrons can move more efficiently, which translates into lower energy expenditure.

The major disadvantage of this type of panel is that they are more expensive than the less durable ones (CIGS) and less efficient ones (polycrystalline). Another problem is that they are rigid. However, everything indicates that this type of panel will begin to extend more and more, thanks to their price and performance.

Polycrystalline

Unlike its monocrystalline sibling, this panel type is bluish; moreover, as we have explained before, it comprises various crystalline silicon cells instead of a single cell.

Even if they are rigid, their small size, low price, and improvements in design have allowed these types of panels to be considered semi-flexible, thanks to the folding system that allows you to put them in any place more comfortably.

The most significant advantage these panels offer us is that they are the cheapest currently available. However, they are the least efficient, being several points below in terms of efficiency compared to their CIGS and monocrystalline colleagues.

How to choose a solar charger?

Many factors can decide to choose one solar charger over another. Let’s see which are the most important:

Solar panel power

Watts (W) indicates the ability of a panel to produce energy to convert sunlight into electricity. However, to produce a certain amount of electricity, other factors must intervene, such as the panel size, the type of photovoltaic panel, the position of the sun, and the weather.

Also, it is essential to know that the more power the solar panel has, it will have a higher number of panels. Therefore, the larger the size of the solar charger will also be.

Charging power

The power output in the charging ports is a determining factor because it determines the speed of charging of connected devices, ie, the more current supplied, the faster a device can be recharged.

Nowadays, it varies according to the manufacturer. However, we can state that the charging ports of solar chargers have a power between 10-12W, providing a maximum current of 2A and 2.4A, respectively, at a voltage of 5V.

On the other hand, it is important to choose a charger that is capable of generating several watts that is capable of recharging a device at an adequate rate, for example, if the solar charger only generates up to 7W, your device will never be able to recharge. at 10W (5V/2A), its output will only be 5W.

Fast charging is far from the world of solar chargers. However, with 10W, you can recharge a smartphone in more or less 2 hours, which is not bad for solar energy.

Charging ports

Another important aspect is to define whether you need one, two, or three USB output ports in your solar charger. Also, the charger must have a DC output if you need to charge a laptop. The more watts (W) the charger can generate, the more devices you can connect.

Efficiency

The efficiency of a solar charger refers to the amount of energy we can get from sunlight. Solar chargers have an efficiency between 21%-23% depending on the type of panel chosen, the light conditions, and the charger’s location.

Portability/design

One of the most common uses for solar chargers is in backpacks, so they charge their devices while we walk on some expedition or trip. For this, it is essential that it is easy to transport the solar charger: folding quickly and efficiently. For example, some models have a magnetic closure so as not to take up too much space. Likewise, their weight must be very light so as not to cause discomfort.

How does a solar charger work? What is its efficiency?

A solar charger supplies direct current from the energy that affects the panel through the so-called photoelectric effect:

The charger panels absorb the photons of light that strike the electrons stored in the photovoltaic cells, interacting with and breaking free from the atoms to which they were initially confined. This allows it to circulate through the material and generate electricity.

Depending on the model of the charger, the photovoltaic or solar cells are grouped, creating one or several independent panels, and then connected in parallel, keeping the output voltage constant at 5V.

Similarly, the ability of a solar charger to convert solar energy into electricity depends – among other factors- on the quality of the integrated panels.

How to properly charge a device with a solar charger?

A solar charger’s electricity (direct current DC) is unlimited as long as the light and the sun’s rays directly affect the solar panel.

Solar charger location

Let’s check these charging conditions with a smartphone and a solar charger from the RAVPower brand:

Solar charger perpendicular rays

As can be seen in the photograph, when the sun’s rays strike perpendicularly, the charger supplies the smartphone with a current of 1.10A.

On the other hand, the efficiency of the recharge drops if the trajectory of the rays is not perpendicular to the panel or affects it with a certain angle of inclination.

Inclined beam solar charger

The efficiency also decreases if any cloud interferes with the trajectory of the sunlight and the window crystal. In this case, photons cannot hit all the electrons when they arrive at the solar panel. If they succeed, they cannot produce an adequate displacement; therefore, the electric energy decreases. Under these conditions, the current flow is significantly lower, so our devices will recharge more slowly.

In conclusion, to obtain the maximum energy efficiency of a solar charger, these factors must be taken into consideration:

Photovoltaic panel

It must be efficient to make the most of the available sunlight to convert it into electricity. Environmental conditions: As expected, the results are not as positive on cloudy days as on sunny days.

Position of the charger

It is recommended to place the panels with an inclination of approximately 30 degrees to hit the sun’s rays perpendicularly. Furthermore, the light axis must strike clearly, without any obstacles. Otherwise, the photons lose part of their energy through those materials.