It seems like some of their panels are single-crystal silicon. That tends to drive the cost up a bit, and it tends to drive up the efficiency.

--B.G.--

I use the Brunton Solaris 26. This is a fold out 26 Watt panel that weighs 28 oz. It's not light, but in my limited testing it reliably charges smaller electronics (iPhone, AA NiMH Battery Charger). It folds out to 22"x38" so hanging it off a backpack will likely be too cumbersome.

I've found this rule to work: "Find out your max power needs, then buy something that promise at least twice that output." A better rule seems to be to set a budget and try to get as much power output you can afford.

I also charge a Lenovo S12 (a 3lb/12 inch screen netbook) with a 3 cell 11.1V 2.4AH battery off the panel. It's questionable if this is wise since the open circuit voltage on the panel is 19-23V, and the notebook wants 20V (input from those with more electronics experience is *really* appreciated :). On a overcast day, I got about 20 % charge off 2 hours of charging.

Solaris 26 product page:
http://www.brunton.com/product.php?id=420

A great review, by a soldier that used it in Iraq:
http://www.amazon.com/review/RIMTJL8E8W9T8/ref=cm_cr_dp_perm?ie=UTF8&ASIN=B000GEFFBO&nodeID=3375251&tag=&linkCode=

Edited by SeanBa on 02/24/2011 17:17:27 MST.

Sean the open circuit voltage of 19-23v is the voltage under no load. When you plug it into your netbook the voltage will drop. Your netbook has a voltage regulator so it should be able to take a range of input voltages.

I'm working on setting up a 7W powerfilm rollable solar panel to hang on my pack for constant charging of my Android Smartphone, which I use for geotracking purposes and taking short videos in the backcountry.

Amazon link:
http://www.amazon.com/Powerfilm-R-7-Rollable-Solar-Charger/dp/B001QKUK6W

The entire system should weigh less than one pound once I finish modifying the electrical connections between the panel and my device. I haven't placed it on the scale yet :)

I have found a great way to mount the panel to the back of my Osprey Exos 46, where it will hopefully receive enough indirect sunlight during the daylight hours to maintain my battery enough for light use. We'll see how the experiment goes: I'm taking a weeklong trip at the end of June and will be posting pics of the system in the MYOG forum once I've finished my hacking...

They are a great unit, the only thing i think, is that you have to keep folding it out to use it, and also the solar panels cost is it actually worth it, or are there more effective technologies to use. What about the actual backpacks with solar cells built in?

http://www.solarjoos.com/products/

I'm curious to see how well it does in the field.

You are going to carry around 1.5 pound of solar panel to recharge your other batteries with?

I can carry a lot of replacement batteries and stay under that weight.

--B.G.--

The Joos is mono-crystalline (looks black - single crystal) - which is a rigid panel - although I believe the mono-crystalline panels are the most efficient by area - an important factor if you're looking to mount a solar panel on a rucksack.

If you're trying to power a smart-phone and GPS, then the 'toy' (generally poly-crystalline - looks like lots of little crystals) panels for <$50 are worthless.

I've used a PowerFilm F15-600 (10W) amorphous silicon foldable panel for charging camera battery 12V + GPS (AAs) with success - however the system was cumbersome for backpack mounting. It's perfect for setting up on the side of a tent - however if you're hiking the whole day, your camp-site may not be in the sun for that long.

I've just acquired a Goal0 Nomad 7 (7W) mono-crystalline system, and am testing it prior to a summer trip in the alps. As a rigid system it is heaver than the powerfilm, but the power provided per area is greater - so it will fit well on a backpack.

Once I've completed some comparative measurements I'll post a review.

Andy.

https://powertraveller.com/