Guide: how to choose a portable solar panel ?

May 2022 - Reading time: 9 minutes

When we go on an expedition lasting several days or weeks, access to electrical energy is an issue that needs to be taken into account. Today, no matter what outdoor activity you plan to do, you’ll often need to have some form of power solution to charge all your electronic devices.

Portable solar panels are becoming more and more efficient and can now be taken everywhere with you during your adventures, without taking up too much space, and without being too fragile. However, there are many different models, and it can be difficult to know which to choose based on price, quality, power, and other characteristics. This article tells you all you need to know on the subject, alongside our advice and tips to further aid your research.

 What is a solar panel ?

Although everyone knows roughly what a solar panel is, it’s always good to go over some basics.
A solar panel is an electrical device that can be photovoltaic (transforming energy into electricity), thermal (transforming energy into heat), or even hybrid (combining the two technologies). It consists of interconnected photovoltaic cells, which produce electricity through a physical-chemical reaction when they come into contact with the sun’s rays.

You can charge several different devices thanks to the USB port(s) on the solar panel: mobile phone, camera battery (e.g. for a GoPro), headlamp batteries, external battery, laptop, and more.

In this article, we will focus more specifically on portable photovoltaic solar panels, which are an adaptation of the conventional solar panels found on the roofs of houses, for example. They are smaller and less powerful but will be more than enough for you during your outdoor activities. Solar power is most commonly used among hikers as the panels easily clip onto the backpack, and can charge all the small devices while we’re busy doing other things, saving you time. In short, it’s always handy to have one with you!

 The main features

Now that we actually know how they work, let’s move on to the features.

 1. Nominal power

This physical characteristic makes it possible to measure the ability of a solar panel to produce electricity under good sunlight conditions.
Depending on the power of the panel (expressed in kW – kilowatts), you will be able to know the charging speed of your electrical device, and therefore the charging time you need. To figure this out, you just need to carry out a simple calculation.
Let’s have a look at an example to get a better idea. For a mobile phone, the battery generally varies between 4 and 5 amps. If your solar panel can deliver 1.2 amps per hour (as is the case for the Sunslice Fusion Flex 6 for example), you will need around three and a half hours to have a full charge of your laptop if it is switched off and charging in good weather conditions (few or no clouds). If it’s on, it’s likely to take a bit longer.

Some applications for phones (which also exist for tablets and other electronic devices) can show you the charging speed of your device based on the outlet its plugged into. On Android, for example, the ‘Ampere’ or ‘Charge Meter’ apps help you find out more about this data, while ‘Ampere Lite’ is available on Apple devices (but this list is not exhaustive) . This can help you compare, for example, the charging time you’ll need when using your panel on a clear day, or on a cloudy or rainy day.

In addition, it is advisable not to charge your electronic devices directly from a solar panel. It is better to use an external battery that you will recharge with the panel, which will then in turn be used to recharge a mobile phone, a tablet, or a drone, etc. The power sources inside the solar panels may not not contain circuitry to regulate the flow of electricity to your belongings, and could therefore potentially cause damage.

 2. Batteries and their storage capacity

Some solar panels may be accompanied by a storage battery which may be integrated into or separate from the panel. Nevertheless, whether you choose one with a supplied battery – or not – it is wiser to always have one with you for the reasons mentioned above.

There are 2 types of solar chargers that you can take along with you in addition to the solar panel itself. They are quite popular and may suit you depending on your needs and activities:

• The ‘classic’ solar panel, which will give you the option to your external battery in advance, so that you can leave your panel in your motorhome or at home and only take the battery when you go hiking or doing any activity. Although a panel does not take up much space, it is always worth saving more space during a long outdoor outing.
• The panel with an integrated battery or portable solar battery (like the Sunslice Photon – 4000 mAh) which is connected to a powerbank type battery and which will allow you to be able to generate energy as soon as the battery runs out. Thanks to this, it will be easy to accumulate photovoltaic energy and transform it into electrical energy in order to store it for later use.

On the left, with the integrated battery. On the right, the ‘classic’ panel.

If you want to have an idea of the capacity of a battery when buying your solar panel with one included, you just have to compare it with the battery of your mobile phone which is generally indicated in mAh (milli ampere-hour) or in Ah (ampere-hour). Indeed, the capacity of a battery for this type of device is generally between 1,300 and 5,000 mAh.

Regarding battery technology, it is constantly improving and varies enormously depending on what you are looking for (in terms of capacity and performance, size, weight, etc.). Indeed, the capacity of the battery and the width of your solar panel will determine the overall efficiency of the charge.

You should know that there are various types of batteries for solar panels:

 3. Output power

The output of a solar panel is a feature to consider when making your choice because it must be equal to the input voltage of the battery of your electronic device or your external battery.

Although, nowadays, most portable solar panels are capable of recharging your small electronic devices (such as your smartphones, tablets, etc.), not all of them are necessarily capable of delivering enough power to successfully recharge a laptop battery. Be careful therefore think about this detail beforehand so as not to be surprised once on the trip.

If you are looking for a solar panel that can charge your small devices, then one with a 5V power output should do the trick. On the otherhand, if you are looking for a portable battery capable of recharging your laptops for example, you will need an output capacity between 12V and 24V.

In itself, the choice of power depends on the use you make of it: if you are hiking, cycling or travelling in a camper van, the weight you have to carry can make you more or less tired in the long term, which makes it a determining factor. If you’re wondering what the weight has to do with it, it’s because the more power a solar panel has, the heavier it is (if it has a built-in battery, that also adds a few grams).

1. If your panel is intended to be worn daily: it is better to be interested in models up to around 40W (for a weight which varies most of the time between 200 and 600 g, depending on the brand, if it has a battery, etc). This should be enough for you if you just want to charge small devices. For example, it is possible to charge your laptop 1 to 4 times with this kind of power.
2. If it’s to leave in a motorhome or in a camper van, you can opt for a panel with a power of 80W (which weighs about 2 kg), or even consider more powerful 200W models (for about 5 kg). With this type of device (such as the Sunslice Fusion 100 for example), it is possible to charge more devices (more or less large: laptop, drone, laptop, etc.) simultaneously. In addition, the weight is not necessarily a problem because it is more easily transportable in a car or a van than when we are on foot. 

 4. Connectors, adapters and other options

Today, almost all portable solar panels are designed to be able to charge at least one mobile phone. To do this, the panel must obviously be equipped with at least one standard USB-A 5V/1A port (more commonly known as USB Type A) in order to insert the USB cables that you already use when charging via mains sockets.

Be careful all the same to pay attention to the connectors: on certain models of laptops. You will need a USB-C output, while for other products you will need USB-A, USB-B cables or other connectors.

Also be aware that it is possible that the charging speed may be slower than with the original charger when plugged into the mains.

Your connection requirements will vary depending on the type of panel you have in your possession.

• If you have a solar panel without a built-in battery, consider checking which output connector it has. Several types of connectors exist, you will just have to make your choice according to those which will be useful to you according to your use and the devices used.
• If it is a solar charger or a panel with integrated battery, all the necessary connectors for charging are usually included.

Some solar panels are equipped with smart charging, which avoids the risk of power surges and will protect the batteries of your devices when they are fully charged.

Others also allow you to activate the charging of your battery or your devices directly when they are in contact with the sun’s rays. Moreover, some even let you know in real time the current delivered by your panel, depending on the level of sunshine.

 Choose your solar panel according to your needs and activities

1. The advantages and disadvantages of having a solar panel with you

 2. The charging time may vary depending on the season, the weather, the activities, and more

First of all, it’s useful to know that the voltaic cells convert only 15 to 20% of the solar radiation absorbed due to load losses. This explains why the charging time may seem a bit lengthy to you.

It can also vary and take a longer or shorter amount of time depending on the weather: obviously, your devices will charge faster if there is a bright sun, rather than if the sky is full of clouds or, worse, if it is raining. . For example, if charging a mobile phone with a 15W solar panel, this will take approximately 2 hours if the sky is clear, and between 3 and 5 hours if the weather is overcast.

The time of day will play a big role too: the charging time will be different if it’s noon or if it’s 17:30 and the sun is setting because the level of sunshine will be lower at that time.

The season during which you use your solar panel also has an impact on the level of sunshine that can be provided to the panel.

 3. When can a solar panel be used ?

Regardless of the activities you want to do and the places you want to visit, whether on foot, by car, on a lake or by the sea, you can make use of a solar panel in various situations:

• On a hike or trek : a panel hanging from a backpack is a good way to charge your devices while on the move, although a solar panel always charges better if it’s static and well exposed. Our advice? Remember to fully charge your devices the day before your departure (as well as your powerbank if you use one) so as not to have any unpleasant surprises once on your way should the sky darken, for example.
• When bivouacking : position the panel on your tent, or on the ground, this will capture energy when you are busy elsewhere.
• When biking : just like on a hike, you can easily clip it to your backpack so it catches all the sun’s rays while you fully enjoy your activity.

But a solar panel is also handy in everyday life, at the beach, at sea, during a trip in a motorhome, and more. You can quickly get a power up, no matter what outdoor activity is planned . Some solar panels are water resistant, and can work in very hot or very cold weather. In short, you just have to choose the panel that will best suit your needs when making your purchase.

However, if you plan to leave only for a weekend or a short period, it is likely that an external battery is enough for you. However, when this runs flat, it becomes a dead weight you still have to carry with you, despite the fact it’s now useless. 

 In conclusion

When trekking, kayaking, or in a motorhome, the solar panel is a highly useful gadget to have at your side during your adventures.
Being able to recharge your mobile phone, and your camera or even laptop battery from the power generated by your solar panel will make you more independent and will allow you to travel without worrying about running out of the battery power you need to keep on track thanks to your GPS which can be recharged in all circumstances.

When choosing which solar panel to purchase, consider which devices you will need to charge the most and in what conditions you are likely to find yourself. If you are going to be close to a lake or the sea, for example, consider choosing one that will be at least waterproof. If you are travelling in a camper van and you have the budget, you can afford to take a solar panel which has a larger load capacity and which is therefore heavier. If you are going on a trip on foot, choose smaller panels that will be sufficient to charge your small devices.

Also remember to bring an external battery to be completely self-sufficient and ensure that you have battery power even in the middle of the night, or during heavy rain.
In short, it should allow you to improve your quality of life as an adventurer if you are used to travelling but are in thrall to power outlets when on the road. With a solar panel, this will be a problem of the past!