I've been researching this for several months myself. This is what I've found, ymmv:

Solio makes a little charger that actually has a caribiner top, intended to be clipped onto a backpack/etc. It's called the "Rocster." reviews vary but shown to be solid. Fairly light for what it is. Charge it for a day for one iPhone recharge.

Solio also makes a more efficient (yet slightly heavier by a few ounces) three panel fan shaped charger. Slightly more expensive, but more solar area for a quicker sun charge. Spoken with several people who have used this particular model strapped to the back of their pack the length of the PCT, JMT, CDT, and AT. One said it wasn't much help in parts OR, most of WA, but still worked ok, just not as well as through CA, fwiw. One was sold last month in the Gear Swap as a matter of fact.

Brunton makes two options viable for backcountry use: the heavier, more powerful option weighs just under 16 ounces and can be juiced up primarily by wall socket or car adapter. Said to hold 7-10 recharges for an iPhone. Costs approximately $175.

The smaller Brunton device weighs 5.5 ounces, costs $44, and charges up the same way as the larger Brunton. It holds approximately 3 to 4 complete iPhone recharges. In addition, it can be used in conjuction with a portable solar powered charger ( such as the Solios) to be recharged itself.

Not sure how far or for how long you'd be off the power grid, but a combo of the smaller Brunton along with either Solio would do you alright.

Alot of cool technical jargon being flung about, but the reviews back up the Brunton claims spot on, and they even break it down between iPhone recharges and other device recharges. Even if cloudy, hiking 10 hours will give you more juice than no juice. iPhones have yet to accept AA batteries. :)

Hope that helped a little, happy solar trails!

Dug
http://thf2.wordpress.com/2011-pct-gear-list/

Edited by Pittsburgh on 01/02/2011 00:56:54 MST.

I just purchased the Solio Classic (3 panel fan) here on Gear Swap and paid about 40% of the retail price for it. The product description looked pretty good to me when I checked their website. The price was good. If it doesn't work as well as Solio claims I'll just put it up on Ebay. Had to look at the product comparisons to get all the info. It weighs about 5.6 oz.

Edited by socalpacker on 01/12/2011 09:30:45 MST.

Sorry, double post.

Edited by skopeo on 01/02/2011 02:47:50 MST.

I use a Solar Focus battery bank that uses 2 AA batteries to charge my various electronics. It has an optional solar panel as well but I didn't buy that as the battery bank seemed to be a better way to go IMO.

It comes with multiple connectors for a wide variety of devices and works well with my camera and has USB connectors that work well with my iPhone.

Weight of the battery pack without batteries is 1.4 oz. The unit weighs 3.4 oz. total with 2 AA Lithium batteries.

I looked at these pretty hard several years ago. They have some strong advantages to backpackers. But the energy density availible through sunlight on a small surface simply is not enough to warent the extra weight. As was said, they can work to keep a set of batteries partially charged. I have a smaller one that came with the Setripen Adventuror Kit. It takes a couple days to get two uses out of a set of batteries. I tried it, it doesn't work all that well. They cannot even maintain enough power to generate the water I needed.

Here in NY, I normally hike through heavy tree cover. Even with the larger sized panels offered by Brunton, it would take about five days to a week to charge a pair of AA batteries. The trade off in weight simply isn't worth it, to me. Like Mike was saying, in my area, I would choose a battery pack over a solar charger. The spare batteries will deliver a lot more wallop over a couple weeks than the solar panels for the weight.

That said, for LONG TERM applications, as was mentioned, they can make sense.

Exactly why the PCT hikers I spoke with said the solar was a weaker option the farther north (and denser tree cover) they got.

The battery bank is a great idea, and the Brunton energy bank I mentioned above is a good deal. I saw you snatch the Solio up in Gear Swap, that was a nice price.

We hiked the JMT this summer north to soutch for three weeks and used a PowerFilm USB + AA Solar Panel Charger to charge AA batteries (Sanyo Enelope) for several devices. We needed daily 2 batteries for our GPS (Oregon 550), every 3-4 days 4 batteries for our SteriPen Classic and every 3-4 days 2 batteries for our camera (Canon PowerShot).
During our preparation hikes we had first experimented with the Solio charger, but that didn't work for our purposes and required to first charge its internal battery and then charge our AA batteries via an adapter.

With the PowerFilm we could charge our AAs directly. It also allows to charge USB devices directly. We never used that feature and I can't say anything about it. When using it you need to have 2 AAs in the charger.
There is also a version that charges 4 AAs instead of 2 which has 6 panels instead of 4 (but doesn't allow USB). We will test it this year on the JMT.

The PowerFilm charger was tied to the top/back of my backpack which is not an optimal angle while hiking south, but we still got all the charges we needed from it.

Dug -

Do the Brunton energy banks allow you to use replaceable (non-rechargeable) batteries as the power source or are they sealed units that must be recharged? I checked out their website but this was unclear. Approximately how many iPhone recharges could you get out of a fully charged energy bank?

My Solar Focus battery pack comes with rechargeable batteries that can charge off my computer or a solar panel but you can also use any AA battery as the power source. This is what I like about the Solar Focus unit... you can carry as many spare batteries as you need.

I've only had my iPhone 4 for a short time so I haven't tested how many charges I can get on a set of Lithium batteries. I can get a full charge out of the rechareable batteries that came with the power pack but they are very old, so not a good test. I would expect much better performance out of a set of AA Lithium batteries.

Manfred:

Sounds like a system that works! Is this the model?





Although the technology / efficiency is steadily improving, the bulk, weight and waiting time still can't match the alternative of throwing in a couple extra rechargeables -- unless one is going on a long trip or thru hike like yours.

I've been fascinated by solar batteries since high school ('70s) and look forward to the day when they become efficient enough to qualify as truly light weight "quick chargers". One day.

Edited by ben2world on 01/02/2011 11:06:16 MST.

Bob, they were strapped to the front of my shoulder straps. And they have an internal battery so no wires have to be attached while strapped on the pack. It worked very well on the jmt as you are above the tree line most of the trip. It still does get charge when cloudy.. obviously not as much as clear sky's..

I did have my iPhone on airplane mode and took the sim card out to maximize battery life. I used it mainly for audiobooks and GPS apps. After a full days charge I would get about 20-25% on iPhone. And i used a lot less than that per day so it stayed fully charged the whole trip. Same with my flip cam..

Jason,

That was my thinking this morning. I rarely use 25% of a full charge on my iPod Touch.
The most I'll use with my Blackberry is about 50% in a day. And, that's a busy day of talking. If it happens to be a day of mostly texting, I use a substantially less.

BTW my iPhone is on the way. Always thinking multi use here.

Anyway, on the occasions when I'll be using my new DeLorme PN-60, I can't imagine using it all day. My estimate is probably 15% of the day at MOST. Honestly, I'll likely only use it 7 - 10% of the time. So, the most charging I'll need is about 35% of a full charge, for my iPod and GPS unit combined, since I never take my Blackberry into the back country. The Solio Classic charger just might work even in low light conditions since a full charge might never be needed.

Edited by socalpacker on 01/02/2011 13:24:31 MST.

Benjamin,

Your picture shows a very similar model.
Ours charged only 2 AAs (not 4 as shown in your picture). Here is a link to our charger





Ours allowed to charge devices directly via USB which would be interesting for this discussion, but was not needed for our purpose.
We use it only for long trips (like going three weeks on the JMT). We like to have our GPS on all the time and geotag our photos afterwards using the track from the GPS. That requires a set of AAs every day. We were able to do that over the whole three weeks (even with cloudy days inbetween) by using it non-stop -- meaning when the LED showed that the batteries were charged, we would exchange them with batteries from one of our devices and keep charging. Since we didn't use the USB capabilities last year on the JMT, we will use this year the model that charges 4 AAs.





It uses 6 panels instead of four and thus charges the batteries faster. It serves our purposes better since we also use the Steripen Classic that requires 4 AA.

Edited by Orienteering on 01/02/2011 15:30:07 MST.

Thanks, Manfred.

I am a huge solar advocate. We have a tent trailer that has 250 watts of panels. Prior to our current trailer we have owned for 5 years, we had another with 120 watts of power. I also have a sophisticated battery monitor that I have used over the years to measure amps in/out, etc. We have not connected our trailer batteries to the electric grid in 7 years. And we have camped well over 700 days and never had a dead battery. So some of the things about our tent trailer are appropriate for this discussion.

Number one: You need to determine how much power your devices will consume each day. That is how many amp hours (AH) you need to replace. Since we use lead acid batteries in our camper we cannot go below 50% of our battery bank's rated capacity, as the batteries can get damaged. Our panels are sized appropriately. In normal weather, even in the winter, our battery bank is usually fully charged by 10:00 AM. We are usually not in the camper during the day, so we need enough capacity to get through the nights. Typically our usage includes lights, water pump for dishes and showers, and operating a forced air heater during the night. We have replaced our 12 volt incandescent light bulbs with 12 volt fluorescent lights, which use less juice. We find LEDs do not work well for general lighting. Our refrigerator runs on LPG. We also have a LPG catalytic heater that uses no electricity and 75% less gas than the furnace. We use that when night temps get into the 30s F or below. The catalytic heater puts out about 50% of the furnace's BTUs and provides radiant heat. So sizing our system included a reduction in electrical consumers.

Number two: solar panels are rated at the max they can put out. With high quality panels like we use (Kyocera) we can get up to 95% of the rated power out of them under ideal conditions. For fixed installations like ours, there are other methods to get the full 100%, but not applicable to this conversation.

Number three: You need to determine how much sunlight your solar panel can collect. In So Cal in summer it is easy to get full power during the middle of the day. The season (e.g. winter) of the year and latitude (e.g. Seattle) can reduce this significantly.

Number four: The panels must be angled directly at the sun for maximum solar collection. This is not too difficult for fixed installations, but impossible while moving. If you cannot tilt panels directly at the sun, then you need a larger solar array.

Number five: Shade is a killer. Because of the construction of most panels, shade hitting 10% or your panel can kill 50% of the output. So a panel on the top of your pack can be cut significantly from the shade of a wide brimmed hat.

Number six: Clouds. Clouds will reduce the power output, but you can still get some output in cloudy weather.

Number seven: You need to size your solar system to anticipate all the items above. That is, you need much more capacity than your can theoretically produce each day.

Number eight: Worrying about charging your system. We do not worry about our panels and don't check the system much anymore. They just sit up on the roof and keep things in balance. We can go for many rainy days, and have enough reserve capacity to get by for a week of constant rain. Although we do not do it, we can power a microwave or an electric toaster. Also will your panel get damaged in use? Our panels are warrantied for 20 years and are designed to withstand hail.

Bottom line: You need to do a lot of research and calculations to size a system, as Bob G has posted earlier. Bad weather and shade can leave you with no power to run your electrical devices. For this reason I do not carry much in the way of devices when backpacking. Normally a camera and a headlight. If the camera goes dead, I will live. A spare battery for the headlamp and it will last for a very long time. A map and compass instead of a GPS 99% of the time. I cannot get cell phone coverage in most places I hike, so it stays in the car. Also if I had to constantly mess around with positioning my solar panel while walking, I would find the trip less enjoyable and frustrating.

Here is a picture of our panels.

You got rid of that Starcraft that you did all those great mods too?!

Nick, it is easy for you to be a big solar advocate. You live in Southern California.

As you start moving north, the practicality of solar reduces. By Portland, it is marginal. By Seattle, forget it.

--B.G.--

>You got rid of that Starcraft that you did all those great mods too?!

Terri, look closely at the upper right of the picture I posted. It is there in the background. I am probably going to give it to my son. I just couldn't part with it when we bought the big one. For those who are wondering what Terri is talking about, the little camper in the background is a very small tent trailer. In 2003 my wife and I gutted it and re-built it from the ground up with amenities that are often found in larger travel trailers.

Terri, I hadn't noticed or put "ncalcamper" together. Good to see you here on BPL!

> Nick, it is easy for you to be a big solar advocate. You live in Southern California.
> As you start moving north, the practicality of solar reduces. By Portland, it is marginal. By Seattle, forget it.

Bob, no argument here. That is why I live where I do. Solar is not for everyone.

Off topic, but...

Nick -- given your experience with solar panels... have you installed them on your house? If so, would love to hear what you did and your resulting experience!

\\As you start moving north, the practicality of solar reduces. By Portland, it is marginal. By Seattle, forget it.

Strongly disagree.
Germany has the highest rate of solar uptake in the world and very high power outputs to the grid, and is approx 51 degrees North.
Yes, it makes it a bit less effective. The poorer weather to the north has a greater impact than anything else (panels can / should be angled quite severely towards the south), but given a reasonable surface area and decent efficiency (especially in how the power will be used) it remains very effective.

My own experience with solar is this - I tried a 3 watt / 5v SolarFocus panel while bike touring in Italy in the middle of summer, and it couldn't keep my iPhone charged using it for about an hour of GPS a day, charging 12 hours a day.

I now have a 10-watt / 12v PowerFilm fold-up panel (it had the best power-to-weight ratio of any panel I looked at. The roll-up ones, and even competitors similar folding models, are heavier).
I plug it into a lightweight Ansmann DigiCharger Vario Pro charging unit that can charge 2 AA/AAA's, USB (for iPhone), 3.6v lithium, 7.2v lithium. And it has a "backup" mode where you can put in a lithium battery and power the USB port from only the battery. It can charge at up to 1000ma (2 hours to charge AA's from dead) in good sun.
So I can charge my headlamp, iPhone, DSLR battery, and Steripen batteries from a single lightweight device at any time of year in overcast skies. It works well and I normally only bring it out when I'm stopped because it charges so quickly.

Edited by dasbin on 01/11/2011 00:45:28 MST.