Even the highest-capacity power banks eventually run out of charge, and then you're stuck until you next reach mains power. Unless, you buy a solar charger. Harnessing their power from the sun's rays, solar chargers are a useful backup to plugging into a power point.

While we haven't quite reached a level of solar to electric conversion efficiency that can let us wave goodbye to using power mains altogether, these nifty solar chargers should get you through those dreaded "critical battery level" moments, so you can move on to more important things (like reading TechAdvisor articles, of course). 

RAVPower Solar Charger 24W Solar Panel

RAVPower Solar Charger 24W Solar Panel

If the convenience of charging your phone simply through the power of daylight isn't enough to sway you, RAVPower's 24W solar panel is also half the weight of similar chargers, which is useful for day trips or camping. It's also foldable and waterproof.

A clever feature is it's iSmart Technology, which can auto-detect the best charging currents for the device you connect to charge. It comes equipped with 3 USB charging ports and two micro-USB cables. 

Keep in mind, this charger is solar-powered only and cannot store any of the converted energy for later, unlike the solar-supported power banks mentioned in this article.

BSAMZ 10000mAh Solar Charger

BSAMZ 10000mAh Solar Charger

The BSAMZ 10000mAh charger comes with 2 USB charging ports, is waterproof, dust-proof, and shock-resistant – making it a useful companion for camping and other outdoor activities (or a rough commute, even). The solar charger bank also comes with a built-in compass and LED flashlight.

BSAMZ recommends using the solar power feature for emergencies, as this method does take longer to charge, but for less than £20 it's practically a steal.

Anker PowerPort Solar Charger

Anker PowerPort Solar Charger

The Anker PowerPort boasts its PowerIQ technology, which detects the fastest charging speed for your device and delivers upto 2.4 amps per port or 3 amps under direct sunlight. The mat charges up to 2 devices at the same time, though it does not store power. 

Foldable, portable and durable, this lightweight charger (it weighs less than 1lb) is made of PET polymer solar panels and polyester canvas, making it suitable for outdoor use. However, Anker does discourage users from overexposing the device to water, though some exposure is fine. 

If you do run into any trouble, Anker offers an 18-month warranty. 

AUKEY Solar Power Bank 12000mAh

AUKEY Solar Power Bank 12000mAh

The AUKEY Solar Power Bank offers a 12000mAh storage capacity, which is enough to charge an iPhone 7 Plus two-and-a-half times. This charger is splash-proof, and like the BSAMZ solar charger, also anti-shock and dust-proof. It comes with two USB ports and a 3.3ft Micro USB cable.

In terms of churning solar power into electric power, this bank offers a conversion rate of 23.5 percent, so if you're only using the daylight to recharge your device, it may take some time. The strength of the sunlight will also affect how fast your bank charges.

AUKEY also offers a 24-month warranty on their products.

While the 12000 mAh model is not available in the US, visitors can find a 20000 mAh versions instead here

Bernet 24000mAh Solar Charger

Bernet 24000mAh Solar Charger

With a whopping 24000mAh capacity, this solar power charger can charge an iPhone 6 nine times and a Galaxy S6 seven times. It charges up to 3 devices at once.

Like some of the other chargers on this list, it is advised to use the solar power in emergencies, only because this process takes longer. Bernet says their charger is still 1.5 times faster than traditional solar chargers, though.

Apart from an 18-month warranty, you also get a Micro USB cable and a nifty USB-powered fan (which you might as well use if you're out charging your device in the sun). 

X-Dneng 15000mAh Solar Charger

X-Dneng 15000mAh Solar Charger

X-Dneng's solar charger is certainly durable. It is waterproof, shock-proof, and designed with circuitry that should prevent overheating and overcharging.

Under direct sunlight, this charger can gain up to 25 percent power at roughly 1 percent per hour. While this may not be an ideal speed, it is still a good alternative to no power at all.  

For the outdoorsy, this charger also comes with a carabiner, so you can clip it to your backpack on your next hiking adventure.

X-Dneng offers a 12-month warranty on this product.