Solar Charging System for CDT Thru-Hike

This same vague question comes up time and time again.

You will never get a good estimate of solar panel power needs until you can estimate your load usage. It does no good at all to mention iPhones or GPS or anything else until you can add up your electrical power need.

For example, if item one uses daily 100 milliampere-hours on +5 Volts, then that means something. If item two uses weekly 500 milliampere-hours on +5 Volts, then that means something. If you never get to that total estimate, then you will be guessing at everything. If you have no estimate of the amount of sun that you will have, then that makes it even more complicated. If you know that the average will be three usable hours of sun per day, then that helps. If you can orient a solar panel at the correct sun angle, then that helps. Some panels can be hung on the back of a backpack to get the sunlight. That makes sense if you are walking away from the Equator, but if you are walking toward the Equator, it becomes much harder. Some panels don't make any sense unless you can lay them out flat on the ground, and most backpackers don't have the time for that.

Weight-wise, you will find it to be much better by eliminating all of the electronic junk. Cut it down to just the minimum necessary, and eliminate the solar panel. Only carry a small number of spare replacement batteries.

If you are bound and determined to buy a solar panel, then some of my friends have bought units in the 5 watt to 10 watt range, but they are charging fewer devices than you mention. The size of the battery might be determined from the degree of sunny versus cloudy days you expect.

–B.G.–

@Bob – it is only a single item the OP is looking to charge. His Iphone 5 which he will use somewhat frequently it seems (phone, GPS, MP3, camera features).

@OP – no experience myself, but Bob's comments seem to make a lot of sense. I know a few AT and PCT folks who've had great success with using battery bricks on their long hikes (I know Portrait (postholer.com/portrait) used one for his AT and I think his PCT hike, and think he is planning on brining it again on his CDT hike this coming year). Many different styles out there — some weigh much less than a tricked out solar charging setup, and you don't have to guess about the sun exposure. Good luck in the search!

Well, as it turns out, there may be more devices as well, like a flashlight, Steripen, and others. The OP still needs to get a grip on his power demand numbers.

Also, you may find that using one all-purpose device like an iPhone is not the best choice, power-wise.

I mean, let's face it. You don't need a cell phone, because you can't get cell service over most of the way anyway. You don't need or even want an MP3 player. A GPS receiver can be handy for difficult navigation areas, but a tiny dedicated GPS receiver might be even better. The camera feature of an iPhone 5 is crap except for simple snapshots.

Now, if you have a device that cannot use replaceable batteries but it can be recharged, then sometimes a battery brick is the solution. Of course, that is not lightweight, either. The best weight savings is from eliminating the unnecessary devices.

–B.G.–

Check out the Eddie Bauer solar charger. It may be just what you are looking for.

Seth- I actually met Portrait and his homemade cuben backpack (which was very cool) on my PCT Thru-Hike this last year. Nice guy, great beard growing technique.

Bob- I will in fact only be charging one item, my iPhone 5. I also, realize that carrying one multi-use item is not the best choice power-wise, which is why I'd be looking to carry a battery brick and solar charging set-up.

I'd be hiking north so hanging on the back of my Arc-Blast would work out. I am not a meteorologist and cannot predict the weather especially 5 months out, so I can't really say how many days of rain and clouds there will be. I don't need a cell-phone but it is nice to have one in town when you are thru-hiking as pay phones are not very common.

I DO want an MP3 player 3000 miles is a long way without music. The phone takes crappy pictures, but I don't really need great quality shots.

Really what I'm asking about is what other people have used in similar set-ups.

Thanks for the advice and I apologize about not knowing more in regards to my power needs.

-Kevin

OP – there is a long solar thread in the MYOG section. There seems to be some folks there that are very knowledgeable about solar charging & battery packs and I think some are using i-phones. I'm sure a PM to one or more of them will get you going in the right direction.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=68387

Used it with my iPhone 4s for months on the Desert Trail and a subsequent adventure. Worked well. Seems like it took about 2 hours to charge the phone up if the battery was very low. I'd have it handy in my pack and when I'd take a break I'd plug it in. It was an especially good option on the Desert Trail because I often wouldn't get into town for many days. The one thing I'd do differently next time is bring a longer than normal charger cable so it would be easier to sit in the shade fiddling with my iPhone while the charger was in the sun. I also learned that although it seemed like it would work great to have it on my pack so I could charge "on-the-fly," if the sun wasn't direct it wouldn't work, and could even drain the battery.

I was using my iPhone a lot, primarily as a camera and GPS, but also to update my journal.

There is a newer generation photovoltaic film out for "thin film" roof tile home
application. This film also uses INFRA-RED radiation, not just visible light, for charging. It is claimed that this can make it 25% more efficient. That may be the max increase in efficiency.

I don't know if it it yet available for backpacking purposes but places like West Marine may know since they sell a lot of solar chargers for boats.

I know this is NOT the response you expected but I would do the math on batteries.

I did some experiments with my iPhone 4S and I can get about 3.5 days of usage if I use it for two hours a night and even if I take pictures. Video wouldn't work though because that is more resource intensive.

My plan was to get the iPhone 5 with a battery extender which would get me about 7 days and then at my resupply points I would ship batters and a charger.

This way I recharge at every resupply point.

The situation with solar chargers IMO is not very good. The battery setup is actually LESS weight. The only upside I can see of a solar charger is using it in the backwoods for WEEKS.

If you were fishing in Alaska or something and didn't expect to see civilization for a LONG time then that would work well.

I couldn't get ANY weight lower than using batteries. It's pretty close to a tie but the battery system was 10-20% lighter.

Also, what happens if you get stuck in rain for a few days.

A big factor for the OP is he's going to be using it as a GPS. I was surprised at how much battery I was going through using my iPhone on the trail compared to at home and it's likely largely because of the GPS usage and much more photography.

I wouldn't take a solar charger on the AT or on short trips. I didn't have a solar charger on the PCT or CDT, but I'd probably take one if I did those trails again with a smart phone.

A solar charger made my hike more enjoyable because I didn't have to carefully ration my battery life. It was fun to take photos whenever I liked and to review them leisurely. I liked taking my time writing up journal entries and to use the GPS when I wanted. I could take full advantage of all the useful functions with the ability to recharge in the field.

What do you do when the sun doesn't come out? All last summer I can only think of one time when that was a significant problem for me, and that was only for a few hours. And I didn't have a spare battery. On the CDT it will be cloudier, but with gear there is always trade-offs, regardless of choices, and like anything, different gear works for different people.