Do you like to take a solar charger with you out into the open? If so, these are the main points you have to focus on:

 
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Weather / Climate / Surroundings

Outdoor means - as is well known - “out-of-doors”, which is as sure as “a solar cell needs the sun”. In the open you have to be prepared to all weathers. Sometimes it’s hot, damp, rainy or bitter cold and wintry. Sometimes you have to face heavy rain showers or even hail storms! That’s what an outdoor solar charger has to come through without being damaged. Otherwise, it’s not worthy of the name.

Mechanical properties
Outdoor equipment has to be designed to withstand many kinds of strains: Once you slip and fall, the solar cell hits the ground. Ordinary solar cells built out of inflexible silicon will burst and immediately cease to work. A bendable, glass-free solar cell is a far better choice for any outdoor purpose.

UV radiation and intense heat require the usage of special plastic. Ordinary plastic tends to become brittle within a very short amount of time.
Finally, you also have to pay attention to size and weight:
As the usable area on your backpack (the motorbike, the boat...) is limited to the size of the bag, it’s of no use to buy solar cells that are way too big to stay fastened to your equipment while you walk. A solar cell has to face the sun as long as possible – thus a foldable, but too large solar panel you usually carry around inside of your backpack is most likely not going to meet your energy needs.

 
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Electrical properties of solar cells

Measurements taken under a blue sky and full midday sun usually look acceptable to the buyer. For most solar systems on the market every single cloud means high performance losses due to their lack of tolerance to shading. As you cannot control lighting conditions you might come across on the road, or hardly ever think of realigning the solar panel towards the sun all the time - you certainly will appreciate solar cells powered by the Triple Junction technology. Multi Junction solar cells are highly tolerant to shading and remain productive even under a dark sky.

»more information on Triple Junction solar cells

Storage battery

Changing light- and weather conditions result in voltage and current fluctuations, which is not quite beneficial to your high-tech electronic devices. They may reduce the performance of your devices or even destroy them.

You also don’t always need the solar electricity at times it’s being produced. Thus you might consider storing it within some rechargeable storage battery.

To compensate conversion loss, such a PowerTank has to be equipped with twice as much storage capacity compared to the battery of the connected gadget. That’s why storage batteries of less then 2000-2500 mAh are of no practical use.
There are several good reasons not to place the storage battery next to the solar cell while it is in use: A solar cell facing full sun warms up to around 70-90°C, but no battery can withstand that kind of strain for a long time. If you happen to be caught in the rain, you’ll be glad to hide the PowerTank inside your tent, while the waterproof solar panel still performs in the open.
Additionally, it is very convenient, if a PowerTank can be charged and discharged at the same time also providing a capacity gauge to check the current status.

»more information on PowerTanks

»more information on solar cells

 
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