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Flexible Solar Panel Project
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Ken Charpie
(kencharpie) - MLife

Locale: Western Oregon
Flexible Solar Panel Project on 05/31/2011 16:40:44 MDT Print View

7 watt rollable powerfilm weight

I'm going to be carrying this for a week-long trip to provide power for the use of gps on my android smartphone. The solar panel will be mounted to the outside of my pack (pics to come) and connected to my phone constantly for trickle charging. Preliminary (backyard!) testing seems promising.

My multimeter appears to be broken :(
But I'm going to try to get better output specs in different lighting conditions. I would like to compare these numbers to my phone's power usage with gps running and a few choice apps being used minimally.

I'm excited to try this out, as it would be lighter than carrying a battery per day (my best guess based on my phone use pattern) on long trips.

The wiring between the panel and my phone will be minimal and I'll provide pics as soon as I finish splicing wires.

I would love to hear about others' experiences with similar projects. I'm pretty excited about this one!

And that's my 17 month old son helping me with the weighing process :) (11.35 ounces)

Edited by kencharpie on 05/31/2011 17:11:14 MDT.

joseph peterson
(sparky) - F

Locale: Southern California
solar panel on 05/31/2011 21:58:13 MDT Print View

To each his own heh hope it works out for ya. Pretty trick. I think it might end up being a hassle, but maybe not.

My blackberry lasted 5 full days on a single charge. Strictly as a camera and clock though as I don't use a gps.

My Droid evo lasts 3, and has a huge screen. Same, camera, video, and clock only.

John Julyan-Gudgeon
(Cyanide) - F

Locale: Red Deer, Alberta, Canada
Works a charm on 05/31/2011 22:56:07 MDT Print View

I have used solarmio and a goalzero solar panels in the past on backpacking trips. I have been able to coordinate keeping an iphone, flash light (AA battery), headlamp (AA battery), PalmPilot (my lightweight), video camera and digital photo camera all fully charged for weeks on end with this set up.

Like I said. Works a charm. But that was back in my 50-80lb pack days. Now that I am aiming for below 16-12 lbs for a base pack, these solar panels may find themselves stuck at home.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Flexible Solar Panel Project on 05/31/2011 23:50:12 MDT Print View

Devil's advocate question...

Say you are hiking south most of the day, with a wide brim hat, like I did all day Saturday. How are you going to keep the panel oriented to the sun. Also, the way panels are constructed, shade on 10% of the panel can reduce output by 50% or more.

I am a solar fan, but have not seen a suitable panel for use while walking.

Have you calculated how much power you will consume in one day, and the amount you need to put back? Most of these panels I have seen are rated at 5 watts or less at 12 - 16 volts depending on manufacturer. It will probably take at least 5 hours of direct sunlight to charge the typical cell phone with a dead battery. This assumes full sun at optimal conditions. Of course it is not sunny every day, we often hike in shade (or try to), and our backs are not always facing the sun.

But let us know how it works. Either way it will be a fun experiment!

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Flexible Solar Panel Project on 06/01/2011 00:01:49 MDT Print View

Nick, those solar panels are not intended for southbound backpackers.

They work fine if you can carry them to one spot, then lay them out facing the direct sun for hours at a time. This is like a basecamp.

Yes, most of those flexible jobs are 5 to 7 watts, maximum. Anything higher in power, and they are way too heavy to carry around. Anything much lower in power, and they don't really do enough good to make it worthwhile.

There are some tiny solar panels that can be mounted on a wide brim of a sun hat. Then you can spin the hat around so that the solar panels are facing the sun.

If you need that much electrical power when you are backpacking, you are going at this all wrong.


Edited by --B.G.-- on 06/02/2011 10:42:16 MDT.

Matthew Pullan
(Skyaddict) - F - MLife

Locale: Steiermark
Re: Flexible Solar Panel Project on 06/01/2011 03:06:54 MDT Print View

Hi Ken,
I have looked at quite a few solar pannels to power my GPS PDA. This is the best one I could find.
Although I would not normally take my PDA I really need one for Para Trekking (tracklog and weather reports are pretty much essential). Including all this electronic gear, and my flying gear, my pack weight is still under 11 KG. By the way there is a 12 watt version available.
MattSunlinq solar pannal (6.5 watt)

Jeremy Platt
(jeremy089786) - F

Locale: Sydney
Paratrekking on 06/01/2011 06:16:02 MDT Print View

Hi Matt,

Just on another note, what does paratrekking involve? Literally trekking on a trail and jumping off a high point with your paraglider? Sounds sweet!

Matthew Pullan
(Skyaddict) - F - MLife

Locale: Steiermark
Re: Paratrekking on 06/01/2011 08:03:37 MDT Print View

Hi Jeremy,
paratrekking is often called by its French name 'Vol Bivouac'. The idea is to fly further than you walk. The open distance record for the Alps is over 300km, if you get good xc weather for say, 4 days in a row, then you can see the potential. Several years alpine flying is a good idea before you start, but the sport is really in its infancy still. The lightest glider weighs about 3 kilos and the lightest harness, about 1.6 Kg. Please pm me if you want more info, I don't want to flood this important thread, cheers.

Daryl and Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Sleep Apnea on 06/01/2011 09:38:04 MDT Print View

Thanks for the info.

Friend of mine has sleep apnea. He hopes to come up with a charger that will allow him to run his anti apnea machine while backpacking. I forwarded this post to him.

Ultra Magnus
(Ultra_Magnus) - F
Re: Flexible Solar Panel Project on 06/01/2011 13:02:32 MDT Print View

Years ago I found this how-to blog post on making your own flexible solar charger that would work for a variety of devices, but it appears as though the website has been taken down.

The link is a little down the page, which tries to take you here:

It's sad, because the instructions were simple and the author posted links for where to source the components (the hardest part of the project if you ask me). I never got around to doing it, and I don't have the page saved anywhere. I may have printed it out, but God only knows where I put it.

Anyone have any google cache voodoo magic that can pull it up some how?


John Nausieda
(Meander) - MLife

Locale: PNW
Try this for your article on 06/01/2011 13:51:18 MDT Print View*/

The site shows 3 crawls . Pick the oldest and select it and the page appears. You may want to convert it into a Word document to save chargerI looked everywhere for a lightweight solar iPod charger. Nothing fancy, just something I could attach to the top of my backpack. I couldn’t find one anywhere, I couldn’t even find instructions on how to build one. So, I set about building one for myself. As this was all about getting very light materials, this set-up is very simple but the charger has no protection from branches, rain, or marmots. Also, understand that I am not an engineer. I have attempted to safely mimmic the power from a USB connections. Namely, 5VDC and less than 500mA. But, this could destroy your iPod, create a rift in space-time or bring about the end of the world. It’s your call, baby. I’m just saying this is how I did it. Device details: Solar iPod charger approx. 2.5 oz. 150mA@5VDC Materials: From Mouser Electronics: 1) Part# 806-KUSBLX-SMTAS1NB, Kycon USB-A female connector. 2) Part# 511-L78M05CV, ST Voltage Regulator, 5.0V 0.5A. From Sundance Solar: 3) Part# 700-50061-00, “PowerFilm” flexible Solar Panel, Model# MPT6-150, 6V,100mA. From various sources: 4) 20 gauge wires, approx 12” long. 5) velcro strip, 1” X 4”. 6) silicone sealant, five minute epoxy or super glue. 7) packing tape. 8) A wee-bit of double-sided tape. 9) solder and flux. 10) exceptionally good coffee. 11) schematics. Tools: 1) soldering iron.2) wire strippers. 3) multi-meter. 4) scissors. The process: 1) I assemble all my stuff:  2) I sip on some exceptionally good JohnnyZu™ coffee. 3) I solder the leads onto the front of the solar panel and wrap them around to the back of the panel. Then I trimmed and tinned all my leads.  4) I attached the two sided tape to the back of the solar panel, stuck on the USB-A connector and voltage regulator and soldered the wiring, using the handy little guide. 5) Then, I attached the multimeter leads to the back of the USB-A connector to ensure my polarity is correct. Simple, huh? 6) After, I sipped more exceptionally good JohnnyZu™ coffee and double checked everything to make sure it is correct. 7) I use the packing tape to secure the wiring that runs from the front side of the panel and wrap the tape around to the front side to insulate the solder spots. Super glue, caulk (careful, it’s heavy), packing tape or five minute epoxy can be used to secure the assembly to the back of the solar panel and to insulate the electrical leads. After building a few of these, I think I prefer to use epoxy to insulate the electrical components and packing tape to cover the whole assembly semi- smoothly. But, I am still refining this part. 8) After the construction is complete, I lightly sand the back of the panel and attach Velcro in order to secure it to my backpack. Thats it. Then I went backpacking. shapeimage_1_link_0shapeimage_1_link_1shapeimage_1_link_3shapeimage_1_link_4

Edited by Meander on 06/01/2011 14:03:00 MDT.

Ultra Magnus
(Ultra_Magnus) - F
web archive on 06/01/2011 14:32:28 MDT Print View

thanks! Apparently I'm incompetent using the web archive site, because I tried it and didn't get anywhere.

It's saved now...


Edited by Ultra_Magnus on 06/01/2011 14:33:01 MDT.

John Julyan-Gudgeon
(Cyanide) - F

Locale: Red Deer, Alberta, Canada
Panel power on 06/01/2011 17:50:47 MDT Print View

I found that, in the Grand Canyon beginning of May, I was able to keep all items fully charged and was able to glutton on them at night. I only need about 4-5 hrs sleep a night, and I also can't sleep much past that. So, I find I am up well past the sun going down. So, out comes the ipod, listening to TED talks, referencing medical journals on iphone, writing memos on important topics on palm pilot, reading further source material with headlamp....further, I like to take lots of pictures, and record my thoughts on video.

So, I draw alot of power at times. The panel I had kept pace with it all. Didn't seem to matter which way I was walking. That said though, it was the Grand Canyon in May, so I think you would get enough light for any solar panel

Peter Peters
(Peterp) - F
Looks great on 06/01/2011 22:51:57 MDT Print View

Looks good, although still a little heavy to be carrying around all the time. Could you get one a little smaller, and still do the job you need, to create good solar power systems for trekking around? Hopefully they get more efficient and lighter, as the BIPV technology because even better.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Looks great on 06/02/2011 00:25:38 MDT Print View

Peter, those are 30 to 200 watt solar panels, and totally irrelevant to the discussion here. Backpackers who convince themselves that they need solar recharging are probably looking for about 5 watts.


Jesse H.
(tacedeous) - MLife

Locale: East Bay, CA
goal0 guide 10 on 06/02/2011 03:23:06 MDT Print View

I picked up a goal0 guide 10 kit from rei, and have done a bit of testing with it, and have been quite impressed, It lives up to it's advertised claims.I really love the design, you can charge 4 AAA (what all my trail electronics can run on) then plug your phone in and be charging your whole kit. pretty slick IMHO I'll be doing some field testing this week, and post my results. Just need to figure out how to charge my d40 with it...

Paul Mountford
(Sparticus) - MLife

Locale: Atlantic Canada
Re: Flexible Solar Panel on 06/02/2011 03:39:02 MDT Print View


Don't bother with the panel you were looking at above. I have it and it only puts out .38 amps and is really insufficient for most applications. I have two of them and when you connect together they will charge an iphone but will do so only slowly. The larger model you mentioned will work but it a little bulky.

There is another thread talking about a 5 watt panel that puts out 1 amp. I will be curious to hear any field reviews on that version.

Ken Charpie
(kencharpie) - MLife

Locale: Western Oregon
WOW! on 06/02/2011 10:30:51 MDT Print View

Paratrekking! Wow, this thread is way cooler than I had hoped.

As to those who think that those wanting a lightweight, renewable energy source to help power their hike are "...going at this all wrong," I say:
Hike your own hike. I like my hike topped with geotagged photos and videos, medical references, and digital copies of my trail guides that weigh less than paper. If you don't think technology belongs in the backcountry, don't bother commenting on a post dedicated to just that. I mean that in the politest way, fellow wilderness wanderers :)

I plan to have some more information on output in different lighting conditions (I need a new multimeter!) in order to have a better idea of what performance to expect. There are so many variables involved (direction, foliage, weather, schedule, etc) that I'm just going to go with my best guess at power usage (1 1200mah battery per day) to compare power output to. I hope to have an all day backyard field test in bright, indirect light; the kind I hope to receive during a normal day of hiking based on my experience. Any efforts at quantifying other variables (exact lumens and positioning variables in relation to direction hiked, etc) seems to be excessive for this project.

I'm pretty excited about the performance I've observed so far and am hoping this will prove to be an efficient charging means for thru hiking and trips lasting longer than one week. If power production by the panel while backpacking proves more than sufficient for my gps needs, I would like to be able to charge my Panasonic GF1's Lithium battery as well.

We'll see how it goes! I have an incredibly simple solution to hanging the panel on my Osprey Exos 46 and the system is feeling rather "zen" if I do say so myself...

Edited by kencharpie on 06/02/2011 10:34:39 MDT.

rick mccoll
(rgmccoll) - F

Locale: East Tennessee
other thoughts/alternatives on 06/03/2011 08:44:17 MDT Print View

here are some alternatives:
same as above

I understand this gizmo is on backorder for a parts issue but it looks promising for backpackers

prototype but could be interesting as well.


Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Re: Flexible Solar Panel on 06/03/2011 14:20:07 MDT Print View

There is another thread talking about a 5 watt panel that puts out 1 amp. I will be curious to hear any field reviews on that version.


It is pretty simple. Amps is watts divided by volts. The trick is an efficient charge controller. Panels do not have charge controllers. They are add-ons.

So a 5 watt panel that is regulated to 5 volts will put out twice as many amps as a 5 watt panel that is regulated to 10 volts... assuming no inefficiencies in the voltage controller.

Most cells in a panel put out .5 volts. Typically most panels are designed for 12 - 18 volts output. So you can adjust the volt output in the design. For portable electronics (especially with USB charging) there are few panels designed to put out 5 volts... thus the need for a charge controller.

For example, the 250 watts on my tent trailer put out 17.7 volts. But since I am re-charging 12 volt wet cell batteries, I need 13.8 -14.2 volts most of the time charging voltage. Also wet cells need an occasional equalizing charge, and need to be temperature compensated for extremes in weather, so I have a sophisticated charge controller that does all of this.


What I liked about that 1 amp 5 watt charger is that it is set up for 5 volts, and it is mono-crystalline construction. The USB is great. the construction is not easily handled like the roll-up panels, which are inferior amorphous panels.