The Best Portable Solar Panel Review

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Putting the BLKBOX 12W to the test on the Big Sur coast. We put our iPod on a rock because it wouldn't fit in the pocket. Note the extendable USB connector on the panel (black). We appreciated this as it likely reduces physical strain on the electrical connection.
Credit: Lyra Pierotti
What is the best solar charger for your phone, tablet, and other small electronics when off the grid? To find out, we took ten contenders and put them in head-to-head tests while on trips all around the country. From mountaineering on Denali to sailing off the California coast, we compared them on the following categories: output power, ease of use, weight, versatility, and portability. In the end we found big differences in the panels we tested. Some worked well for all of our needs and some barely charged anything. We also found there is not one best panel for all needs. Read on to find out which is the best solar charger for your application.

We hope that this review will help illuminate some of the pros, cons, and glitches of solar charging systems. Our our Buying Advice article goes more in depth on the different types of panels on the market.

You may also be interested in the related External Battery Review

Read the full review below >

Review by: and Chris McNamara

Top Ranked Solar Chargers Displaying 1 - 5 of 10 << Previous | View All | Next >>
Our Ranking #1 #2 #3 #4 #5
Product Name
Instapark Mercury 10
Instapark Mercury 10
Read the Review
Video video review
Poweradd Apollo 2
Poweradd Apollo 2
Read the Review
Anker 14W Foldable Dual Port Solar Panel
Anker 14W Foldable Dual Port Solar Panel
Read the Review
SolarMonkey Adventurer
SolarMonkey Adventurer
Read the Review
SunTactics sCharger-5 Portable USB Charger
SunTactics sCharger-5 Portable USB Charger
Read the Review
Editors' Awards  Editors' Choice Award  Top Pick Award  Best Buy Award     
Street Price $50
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$130
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Pros Light, inexpensive, simple, can charge two devices at onceDurable, powerful, integrated battery, easy to use, small/compact, discreteInexpensive, easy to use, durable, simple, powerfulLight, simple, charges tablets, internal battery, good low light performanceSimple design, durable, good manufacturing, relatively light
Cons Only charges USB devicesA little heavy for the size (but it includes a battery), slow chargingOn the heavier side for a panel of its sizeCan't charge multiple devicesFeatures not streamlined for easy use, single USB charging port
Best Uses Backpacking, sailing, hiking, car campingClimbing, expeditions, mountaineering, around town, camping, backpacking, hikingGeneral outdoor use, camping, basecamp, mountaineering, sailing, kayakingBackpacking, sailing, hiking, car campingCamping, backpacking, general outdoor use
Date Reviewed Dec 15, 2014Dec 15, 2014Dec 15, 2014Dec 15, 2014Dec 15, 2014
Weighted Scores Instapark Mercury 10 Poweradd Apollo 2 Anker 14W Foldable Dual Port Solar Panel SolarMonkey Adventurer SunTactics sCharger-5 Portable USB Charger
Output Power - 30%
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Ease Of Use - 15%
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Weight - 20%
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Versatility - 15%
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Portability - 20%
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Product Specs Instapark Mercury 10 Poweradd Apollo 2 Anker 14W Foldable Dual Port Solar Panel SolarMonkey Adventurer SunTactics sCharger-5 Portable USB Charger
Panel Type monocrystalline monocrystalline monocrystalline monocrystalline monocrystalline
Size folded (inches) 9 x 6 x 2 5.91 x 2.95 x 0.59 6.9 x 1 x 11 6.75 x 3.5 x 0.8 6 x 5.6
Size opened (inches) 9 x 22 x 0.5 same 34.6 x 11 double when open 6 x 11.5
Panel Size (watts) 10 5 14 3 5
Max Output Power (watts) 10 10.5 10 3.5 5
Max output (volts) 5 / 5 5 / 5 5 5 5
Max Output Current (amps per port) 2 1.3 / 2.1 2 / 2 0.7 1
Internal Battery No yes - Li Ion polymer no Yes no
Weight 12 oz 9.4 oz 27 oz 9.6 oz 8.4 oz
Charge iPhone/smartphone Yes yes yes yes yes
Charge tablet Yes yes yes Yes yes
Charge laptop? No no no No no
Direct USB Plug? Yes yes yes Yes yes
# of USB outlets 2 2 2 1 1
Daisy Chain? No no no No no
12-Volt cigarette adapter No no no No no
Warranty 1 year 1 year 18 month 1 year 2-5 years

OutdoorGearLab Editors' Hands-on Review



Selecting the Right Product
Solar panel technology has come a long way in a short amount of time. Not long ago, it was unrealistic to get a rigid monocrystalline panel into a portable, foldable design. Thin film photovoltaic technologies filled a niche as a more portable option, but these are not the most durable. Today, we find a healthy mix of both styles of panels on the market, and you can choose between super efficient charging (monocrystalline) or ultra lightweight (mostly thin film CIGS in outdoor gear), and a dizzying assortment of features, accessories, and qualities on the spectrum between the two.

In general, if you want a very light and more affordable solar panel, look at the flexible CIGS panels. If you want a more timeless piece, consider a rigid monocrystalline folding panel, such as the Anker 14W Foldable Dual Port Solar Panel, the Goal Zero Nomad 13, or the Instapark Mercury 10, to name a few from our review. These are bulkier and heavier, but significantly more durable. CIGS or thin-film panels tend to degrade or delaminate over time. As technology improves, however, companies are making monocrystalline panels more and more portable, which is great, as these panels are still much more efficient than thin-film panels. The Poweradd Apollo 2 is a good example of a portable, efficient, and relatively light monocrystalline panel that we really liked. To learn more about panel types, reference our Buying Advice article.

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A side-by-side look at several of the solar chargers in our review. From top to bottom, left to right: Bear Gryll's SolarWrap Mini (hanging), Anker 14W, Instapark Mercury 10, BLKBOK 12W, SunTactics sCharger-5, and Poweradd Apollo 2.
Credit: Lyra Pierotti

Before we get started, a short anecdote about this review:

We ordered a very diverse array of solar chargers, some with batteries, some without; some pocket-sized, some not so much; and we tried many different companies to see what they all have to offer. In our first round of testing, there was one that we just couldn't get to charge in all of its advertised capacities. It had a huge assortment of laptop plug adapters, but we could never get them to work, and there was no adapter for any Apple product (red flag!). Finally, we gave up and emailed the company. We got a very polite but useless email back, and quickly identified that it was a very, very good copycat. The packaging and everything looked identical, but it was not the reputable brand it looked to be.

This is our way of saying: be discerning in your search! Sometimes it is worthwhile to spend a few extra bucks for a reputable brand. This review will help identify several brands that are good or less good, and how to sift through the hype.

Wait, Let's Talk a Little About External Batteries
Before we get into this review, we want to highlight that many people may be better served by an external battery. External batteries often charge a smartphone 3-6 times, can be used when it's not sunny, are compact, and usually cost a fraction of the cost of solar panels or solar panels with built in batteries. If you only need 3-6 charges of your device, we recommend checking out external batteries. We have a complete External Battery Review.

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When the InstaPark Mercury 10 is paired with an external battery, it's by far the best value in a panel and battery combo.
Credit: Chris McNamara

Criteria for Evaluation

Output Power
In our past reviews, there was a high correlation between the watt rating and the highest output power of the panel. A 10-watt panel, for example, was generally about two times more powerful than a 5-watt panel. Some years later, the technology has changed significantly enough that we started to notice some quality discrepancies. The simple watt rating is clearly no longer the best metric from which to judge a panel's charging proficiency.

This is a little confusing so here is an example: The SolarMonkey Adventurer and Joos Orange are only rated to 3 watts, and yet both are able to charge iPads and reliably charge iPhones. The Goal Zero Nomad 7 has a watt rating that is 2+ times higher (7 watts) and yet could not charge an iPad and ran into issues when charging an iPad mini or iPhones. This is likely due to amperage (current) being too low. The Apollo 2 is very instructive on this issue: it has two USB ports, one at 1.3 amps (labeled for smartphone) and the other at 2.1 (labeled for tablet). The 2.1A port charges an iPad visibly faster than the 1.3A port.

The Goal Zero Nomad 13 has the highest output power of all the panels we tested. The Poweradd Apollo 2 has a max output of 10.5 watts, and the Instapark Mercury 10 has 10 watts. Both of these fall behind the Nomad if all you look at is the wattage--but they both have USB ports with higher amperage. If your main goal is to charge two phones and/or tablets, the latter two will get the job done faster.

Ease of Use
This category is a catch-all for the overall quality of a panel--this is where we assess if a panel is too glitchy or counterintuitive, or if it is so slick you don't even notice it in your life. In the field, this can mean many things, from tie-down or hanging options to stash pockets for your device. More and more, panels are starting to charge exclusively USB devices. This means that the panel can be easily shared with multiple different devices and smart phones. All you need is your device's charging cable. This is a welcome change from panels of the past, when they came with so many adapters it looked like a socket wrench set (and required near OCD skills to keep everything organized.).

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The Instapark Mercury 10 set out upside down to show the inside of the pocket, the special USB iPad port with higher amperage for tablets, and the scale compared to an average smartphone.
Credit: Lyra Pierotti

We found panels that include a sewn-on storage pouch to be immensely convenient. They provide a convenient place to store your charging cables, and keeps your device clean and out of the wind or direct sun while charging. Our favorite pockets were on the Goal Zero Nomad 13 and the Instapark Mercury 10. The Nomad's mesh pocket is big enough to hold an iPad. The Mercury 10's pouch houses two USB ports, and is generous enough to hold your phone, an extra battery, and the USB charging cable. The Anker 14W Foldable Dual Port Solar Panel had the weakest pouch closure we used, which was annoying at times and would not handle overstuffing (but would hold a smartphone and USB cord well enough). The BLKBOX 12 had such a small pouch that it was not useful at all. The SunTactics sCharger-5 came in a separate bag which doubles as a handy (but detached) pouch for your device. The SolarMonkey Adventurer also comes in a zipper pouch that can hold charging cords.

The Mercury 10 comes with string loops attached at the corners which allow you to hang the panel from bushes or hooks or tents, etc. The only panels that scored higher in this specific sub-category were the ones with metal grommets instead of string--this attachment is far more durable!

A panel like the Joos Orange gets a mixed ease-of-use score. There is no direct USB connection, so you have to always remember the Joos cord and an adapter and possibly your USB charging cable. On the other hand, it is the only panel that is self-supporting and can be easily oriented perpendicular to the sun.

Weight
Weight gets high weighting in our scores. After all, the whole point of a portable solar panel is to be, well, portable. A panel that weighs less than a pound and is very compact is generally all we take for most outdoor situations: hiking, backpacking, biking, and climbing. If the panel weighs more than a pound and a half, it really needs to do some heavy duty charging of multiple devices and/or a laptop and is probably not ideal for carrying on a self-supported trip. If you are boating, weight doesn't really matter. Take that into account when looking at the scores.

Also, consider that weight will increase if you need to bring multiple charging cables and/or a case. The weights in our spec sheet only include the weight of the panel.

The clear winner here was the Poweradd Apollo 2. It is not only light, it is also very compact. It fits in most jacket pockets and we could even squeeze it into many pants pockets.

The heaviest in our test is the Anker 14W Foldable Dual Port Solar Panel at 27 ounces and the lightest is the Bear Grylls Solarwrap Mini at 3.1 ounces. Highly versatile, powerful, or otherwise practical panels did not get penalized if they had a bit more weight but added a lot of usability: for example, the Apollo 2, while heavy for its size, was not penalized as much in this category because a lot of that extra weight is due to the fact that the Apollo 2 has a battery incorporated, which is immensely useful.

Portability
With the entire internet at your fingertips, in a device small enough to fit in your pocket, who wants to carry around a big, bulky solar charger? Fortunately, the days of cumbersome solar are over. The market is flooded with lightweight, simple, and very compact panels--and the deluge of design and innovation doesn't appear to be slowing any time soon.

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Testing solar chargers on a big wall in Yosemite, California. Spending days on a wall is a perfect application for portable solar panels.
Credit: Chris McNamara

Mostly, we were looking for devices that are light, and not cumbersome. It's a brave new world--solar technology has emerged from the realm of electrogeek to sexy cyber chic.

One of the most eye-catching additions to the solar scene in recent years has been Poweradd's Apollo series. The Poweradd Apollo 2, reviewed here, looks a lot like a smart phone, and we all know how cool it is to walk around with a flashy and oversized phone peeking out of your back pocket these days. (Our reviewers are, for better or worse, a product of their generation.) Braving the judgment that may ensue (and admitting we are also dating ourselves a bit here), we were initially drawn to the Apollo 2 because, well, it looked cool. But as vigilant reviewers, we put it to the test and scrutinized it with our keen sense of consumer skepticism. In the end, we were impressed--it was just as cool on the inside.

Versatility
Versatility is important to some and trivial to others. If all you need to do is charge a cell phone, you can gloss over this metric. For a simple phone-charger, all you need is a lightweight device with a USB port.

However, if you want to charge multiple devices and bigger devices like a laptop, then versatility is much more important. The Nomad 13 is the highest rated in this category because it can charge so many different devices. If you have other Goal Zero batteries and lights, it can charge even more. It is also one of the few panels that can be daisy-chained with others.

Accessories
Many people choose to combine a solar charger that doesn't have an internal battery with an external battery. This allows the panel to charge the battery during the day while the device is being used. Then the device can be charged at night from the external battery. We recommend the Anker 2nd Gen Astro2 9000mAh and the RavPower Luster Mini 3000mAh for this use. For a full list of all the external batteries we reviewed check out The Best External Battery Review.

Home Solar Panels
The world headquarters of our sister site, SuperTopo.com, is now solar powered. Check out this detailed guide on how to choose home solar panels. The article contains photos, video, and many external links to help you evaluate if going solar is right for you.

Editors' Choice Award: Instapark Mercury 10
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Checking out the Instapark Mercury 10 on the rocky shores of Icicle Creek, in sunny eastern Washington. This is a durable yet portable monocrystalline panel.
Credit: Lyra Pierotti

The Instapark Mercury 10 is a great deal in portable solar technology. With 10 watts of power, two USB ports, and minimal weight, it continues to blow the competition out of the water. It is versatile, easy to use, and affordable. If your main need is to charge a cell phone or small electronic devices, this is an excellent option. When combined with an external battery, you can set yourself up with a smartphone and tablet charging powerhouse, all for under $100. This was one of the few panels with two USB charging ports. It has one of the most generous external pockets for holding your phone, cables, and an extra battery (more than a welcome luxury--this keeps your devices safe in blowing sand or snow). The downside to this panel is you can't plug in a barrel adapter for charging anything that needs a 12-volt (cigarette lighter) connector.

The field of solar panels is only getting more and more competitive. Instapark Mercury 10 won our Best Buy award in the past, but the market has been flooded with other affordable options. It has also been flooded with more low-end options. As such, the Instapark has found a new award, and we bumped it up to our Editors' Choice award for its hiqh quality and overall value--it has the whole package.

Best Buy Award: Anker 14W Foldable
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The Anker 14W Foldable Dual Port Panel charging a smartphone on Icicle Creek in eastern Washington.
Credit: Lyra Pierotti

The Anker 14W Foldable Dual Port Solar Panel is the best bang for your buck. It is on the heavier side of the panels we tested, but it packs so much charging power that we feel it is well worth it, with little sacrifice to versatility. What it lacks in the lightweight category, it made up for with a slender and packable design.

The panel is under $70, which made our reviewers do a double take. Anker is a reputable brand which also makes excellent external batteries, so this is a great company to consider if you're looking for a full solar kit, including a panel and a battery for storage.

This panel is just simple and easy to use, and after a lot of use it showed no wear, and revealed no glitching or reduction in performance. This is a great investment (without the sticker shock that often comes with things labeled "investments"), because it will last for many trips, and many charges.

Top Pick Award for Best Panel with Integrated Battery: Poweradd Apollo 2
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With the ability to charge a device directly through a USB or store charge in an internal battery, this handy solar charger kept two testers reading eBooks and playing Angry Birds on their smartphones for fifteen days while camped on the Kahiltna glacier.
Credit: McKenzie Long
The Poweradd Apollo 2 is a remarkable device, especially for its size. It is sleek and stylish, as cool looking as a smartphone, and easy to carry with you on any outing, from a lengthy expedition to errands around town--and it will serve you well on both. The most impressive feature of this solar charger, aside from its integration of a very efficient solar panel (though small) and a fairly efficient battery, is how fast it charges smartphones and tablets. It pumped up our iPad as fast as if we had plugged it into an outlet at home. We were psyched.

Though this device takes 10 hours to charge in a wall outlet and up to 50 to charge in the sun, since you can get three to four smartphone charges on one battery charge (or up to two tablet charges), we found it surprisingly difficult to empty the battery. Since we had so much time to find sunlight and recharge a little, there was always juice to be had when we needed it.

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The generous pouch on the Nomad 13 holds the Sherpa 50 battery pack, cables, and extras.
Credit: Chris McNamara
Top Pick Award for for More Serious Charging: Goal Zero Nomad 13
The Goal Zero Nomad 13 is the best for charging multiple devices and incorporating with other batteries and accessories. It is the only panel in our test that is set-up for daisy-chaining with other panels to create a lot of power. If combined with a battery pack, it can also charge a laptop. If you have serious charging needs but still need a portable solution, this is the panel to get.

Ask an Expert: Patrick Sherwin
Patrick Sherwin has been an innovator in the solar industry for the last 15 years. He's a LEED and NABCEP certified installer and owns his own solar panel installation company, has developed solar integrated electric vehicle charging stations, and has spent over two years living off the grid in the Bahamas and Ohio. His latest invention, the Go Sun Stove, is a high-efficiency portable solar cooker that uses nothing but the sun's rays to bake, boil, or stew your food. Patrick shared his expertise on how to choose the best solar setup for your needs.

What's the longest amount of time you've used a portable solar charger for?
The longest I've lived off the grid expedition style was a two month trip down the Amazon River in Peru. We used a Brunton SolarRoll Solar Panel to power our trip, and that kept our satellite phone, laptops, and camera batteries charged for weeks at a time.

How do you figure out what size panel or system you need?
I rarely say this in life, but in the case of solar charging, I do think bigger is better. You might only want a system to charge your phone, but then out in the field your buddy needs his phone charged too, so now you need double the capacity. Then you might buy a rechargeable headlamp and start growing in your consumption. So you want to try and size it right from the beginning.

First, calculate how many appliances you want to charge, say a phone, a camera, and two flashlights, and then calculate the wattage needed to charge them. Once you know how much it takes to charge those four appliances, you need to keep in mind that the system's ratings are what could happen in the ideal scenario, but how often are you operating in those perfect conditions? It might be 5 pm, or it's partially cloudy and the panels are super dusty and muddy, so maybe you actually need double the wattage. That's why it's always important to go bigger.

You then need to consider how many days you will be out relying on the charger, and you can also add in the metric used in off-grid system design, which is 'days of autonomy,' or how many days you might go without any input from the sun. Days of autonomy depend heavily on where you live. In Ohio, when I do off-grid design I calculate three days, but in the desert southwest you can generally just use one. The longer you plan to be out and the more days of autonomy that you add, the more expensive and heavy your battery system is going to be.

What features do you look for in a portable charger?
I prefer using the mono and multi crystalline technology over the amorphous thin-film designs. The crystalline panels are a more proven design, more efficient, and generally take up less space. Another reason I prefer the more rigid and/or foldable panels is because the surface treatment of the cells can be rigid as well. Flexible surface treatments, like on the roll-up models, can delaminate over time, and are more difficult to clean because they are rubberized. Foldable panels can be just as lightweight as a rolled up one, because it takes less surface area to generate the same amount of power. Finally, crystalline panels have a lower per/watt cost than thin-film ones, but while they can handle some impact, if you crack the cell they won't work anymore.

The user interface is also key, and that technology has improved a lot over time. Ten years ago they had a bunch of alligator clips and loose wires, and it was a very backyard do-it-yourself ethic. Wires would often spark when plugged in, which wasn't dangerous but definitely disconcerting to a novice user. This is where companies like Goal Zero have done a great job of creating user centered modules that are much more plug and play.

What determines the efficiency of a panel?
Efficiency is a rating of how much of the sun's input a panel is capable of converting to energy. It just so happens that peak sunlight produces about 1000 watts per square meter. That is a universal constant at high noon in July, and that is the standard test conditions that manufacturers run from, but that is not the reality all the time. The efficiency of this kind of micro solar really tends to vary a lot, and is determined by the cell technology, or the silicone's ability to convert sunlight into electricity, and then the efficiency of the entire assembly.

For mono and multi crystalline panels, the average efficiency is about 15%, with 20% being the high end. Then there is an entirely different style of panel, which is the amorphous silicon or thin-film design. The amorphous silicone allows the photoactive layer to be 'painted' on the base layer, which can be a flexible material. This helps to create a more portable unit, but it is not as efficient as the rigid style, typically only getting around 8%.

So you would need about twice the surface area of thin-film solar to produce the same power as a rigid panel. This is generally not that big of an issue when talking about a household array or a solar field, because there is a lot of space, but in the portable world you want something that's lightweight and easy to transport. Figuring out how to create foldable panels of crystalline cells was a huge advancement over the thin-film design, because now you can have an efficiency of 15% in the field.

Would you recommend buying a unit with an external battery? Or just going with an external battery instead of a solar charger?
It is really smart to have the battery integrated into the design. It's not critical, but when you are buying a system it is important to consider the loads what are you powering, for how long and when (what time of day). This is the basis of off-grid design. When you are living off the grid the reality is that it's not about living off solar, it's about living off battery. I would recommend getting an integrated system where the battery and panels are matched to each other to cooperate consistently. Then what you really work towards is powering the battery, which becomes the hub that you can pull energy from when needed.

In many cases you can size an external battery to suit your needs instead. I carry around a lithium ion battery that can charge my phone three times, and it only weighs a pound. So I can power that up during the day with a 10 watt solar panel, and charge my phone off of that.

In our testing, we found that some of the ratings did not correlate with the actual power output. Why is that?
The misleading thing with solar panels is that they will create voltage very easily and under minimal light conditions. When manufacturers are rating panels they might have more emphasis on flash testing, which will produce misleading results. Testing devices can measure how much voltage is created by the cells, and then the watt rating is determined by multiplying it by the amperage, or current, but if the amperage is over estimated then the overall rating will be skewed.

The panel might create a high enough voltage to charge your phone, but there might not actually be enough current to make that happen due to the small size of the unit and also the efficiency of the panel. So it's easy for manufacturers to convince folks based on their testing procedures that a panel produces 8 watts when in reality it never makes that much.

How important is it to properly orient your panel and what's the best way to do so?
It is really important to get the right orientation. You have to make sure that you are perpendicular to the sun within plus or minus 20 degrees, and that's called the tilt angle. The other angle is east to west, called azimuth, which is equally important. Both of these angles are hard to achieve when you are travelling and moving. Getting the right angle is a critical issue when winter camping, as you have to really get a steep tilt angle in order to capture sunlight. It is less of an issue in summertime travel or tropical locations, when orienting it horizontally is just fine, as you will likely fall into that 20 degree window or so.

You rarely want to put the panel in a vertical position, say hanging off a table or a backpack. You almost always want to put it horizontally, except in winter months when the sun angle is super low.

One design feature is that a panel will have hooks that you can use to attach it to your pack when hiking. Are you realistically going to get much charge from that?
Probably not much. Maybe if you have a smart battery that can handle constant changes in voltages. I think you are better off putting it on the brain of the backpack, on the very top where it's mostly flat. In all honesty, I'm not really feeling this whole wearable solar trend. The production is just so minimal.

What sort of maintenance do you need to do to increase the charging performance and longevity of the panel?
Keeping the panel clean is very important, particularly on the surface that's collecting sunlight, and to do that you should use a non-abrasive cloth and cleaning solution. A little dust might only give a 5% reduction in performance, but if it's covered with mud then it's not going to work very well. Dust and dirt are your main maintenance concerns.

There is the potential to have some corrosion on your connectors, and so you want to keep an eye on that. An easy way to deal with corrosion is to use a little sandpaper to clear it out.

Any good solar energy stories you want to share with us?
During my expedition in the Amazon, we ended up at a remote ranger station, called a 'point of vigilance' against illegal logging. The station was being threatened by illegal loggers who were taking old growth trees from very remote parts of a protected area of the jungle, and the rangers were having trouble communicating via radio to their main office. They were worried that they were going to get ambushed and would have to abandon their post for their own safety. When we arrived, we had some tools with us and we took a look at their solar system, and sure enough so much corrosion had built up on all the terminals and all the terminations that it was probably running at only a quarter power. We rewired their system, cleaned it up and got it running, and they maintained their point of vigilance.

History of Solar Chargers
By Andy Wellman
Humans have been trying to harness the power of the sun for millennia. 2700 years ago we were using magnifying glasses to start fires, and the use of passive solar technology has been recorded throughout the ages since. The ability to turn the sun's energy into electricity was first discovered in 1839 by a French scientist name Edmond Becquerel. He found that when he placed two metal electrodes in a conducting solution and then exposed it to light, electricity generation increased, and he dubbed this 'the photovoltaic effect.' It still took over another century for the modern silicon based photovoltaic (PV) cell to come into being, thanks to work done at Bell Labs in the 1950s, and the technology was quickly adopted by the space industry for use on satellites. At that time, it cost around $200 to produce 1watt of power.

The 1970's saw greater use of PV cell technology thanks to a decrease in costs, as well as oil insecurity. The first homes that ran on solar energy were built, and 'thin film' solar cells were developed. In the 80's and 90's the first large scale solar power plants were constructed, and solar panels started to appear all over, from experimental cars and planes to the basic calculator that every kid took to school. As the efficiency of PV cells increased and the per watt cost continued to decrease, household solar arrays became more frequent and some do-it-yourselfers were fashioning their own solar chargers using single panels and car batteries. In fact, keeping a car battery topped off was one of the original consumer demands for this technology, and solar battery chargers are still commonly sold today.
The other demand for portable solar came from the outdoor industry. As our use of electronics in the field increased (such as satellite phones and laptops to update expedition blogs), so too did our need to power them. The first portable commercial solar chargers came on the market a little over a decade ago. Brunton was an early adopter of the technology, though their first chargers were more rudimentary and required a bit of electrical know-how. The first computer laptop solar charger debuted at the Consumer Electronics show in 2008, with a 15 watt panel that could charge a standard laptop in a few hours.

Goal Zero revolutionized the solar charger market when it launched in 2009, with an emphasis on design, ease of use, and humanitarian focus. While solar chargers might be a niche camping or survivalist trend in North America, in the developing world or in disaster relief situations it has lifesaving implications. Goal Zero has donated hundreds of thousands dollars' worth of merchandise to people afflicted by large scale disasters, such as the earthquake in Haiti in 2010, the Japan earthquake and tsunami in 2011, and Hurricane Sandy in 2012.

Today, the use of solar energy continues to grow at an exponential rate. Over the last decade, global production has increased 53 times, from 3.7 gigawatts in 2004 to a staggering 138 gigawatts today. Costs have decreased to less than $1/watt for large scale productions and an average of around $5 per watt for household arrays (however portable costs are still in the $10-20/watt range). Though portable solar is still a small slice of the overall energy production, is does fulfill a critical need in many situations.

Lyra Pierotti and Chris McNamara
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by Lyra Pierotti and Chris McNamara
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