Solar charger for iPad/iPhone
October 27, 2010 7:30 PM   Subscribe

iPhone/iPad Solar charger to use whilst hiking?

Hi all, I would love to get the advise of the hive mind! When we go hiking I love to pack my iPad to read on at night but on extended trips I have problems with my battery running out. Ideally I would love a solar charger that clips on to my pack and charges a battery that I could later plug into my iPad. I would like to hear from people who have tried solar charges before or can point me in the direction of some reviews.
posted by Eapoe to Sports, Hobbies, & Recreation (5 answers total) 6 users marked this as a favorite
There's a portable solar charger in the most recent Skymall catalogs that looks like it would suit. I haven't used it personally.

There are a couple others for sale on that website too, if you search for "solar charger" you'll find them.
posted by hootenatty at 8:27 PM on October 27, 2010

REI has them.
But, remember:
- you can't depend on it being a cloudless day
- it will be a challenge to aim it at the sun while hiking

Check the reviews for the one that suits you & your Pad.
posted by artdrectr at 9:34 PM on October 27, 2010

Holy crap, it's a 25 watt-hour battery, at 3.75 volts!

Coulombic efficiency is about 100%, so you're going to need 25 watt-hours
on a moving platform, so we'll assume that you take a 50% hit in solar collection.
Let's say you need to fully recharge it every day, because you are going to listen
to music with it all the damn day, and read with it at night.

We'll assume 8 hours of solar charging a day, at 50 percent efficiency. You're going to
need at least 5 watt panel to do the job. 7 watts would do better.
Powerfilm makes them. F15-300 5w Folding Solar Panel Charger looks light.

You're also going to need some kind of DC-DC converter, or an inverter, to get the
power to something that you can interface to your ipad so it can charge. And I don't
know how the charge process is going to handle being periodically and randomly shut
off by shading, shadows, or bad weather; and then restarted.
posted by the Real Dan at 9:53 PM on October 27, 2010

I've tried similar things for cycling around Tasmania.

Solar chargers, at least the ones I tried, don't work at all well. Hand cranking seemed to be a better option.

A setup that will absolutely, definitely work for reading is getting a cheap Kindle. The new $140 one is excellent. I've been travelling around Europe and have read 5 books on my Kindle over the past week and a half or so of flying from Australia, sitting on trains and waiting around and whatnot. I charged it last night, but it was actually at half charge and could probably have gone another few books.

If you got a lantern with wind up charging and a Kindle you would be set for days and possibly weeks of reading. The Kindle is also very, very light.
posted by sien at 12:22 AM on October 28, 2010

This page suggests that you want at least a 5W and preferably a 10W charger. More importantly, you want 1~2 amps at 5V. The iPad is a hungry beast.

IMHO, most of the solar chargers listed above would be fine for an MP3 player or a standard mobile phone, but lack the power for an iPad. The higher power charges are outputting a higher voltage (~15V) and are typically used to keep a 12V battery charged. You could use a car USB charger to adapt the 15V to the 5V needed, but you will lose quite a lot in the translation (car chargers are probably not that efficient). So my advice would be to but the biggest solar charge you can afford (~20W) with a money back guarantee in case it doesn't work.

Lastly, all these chargers are really made to sit still in full sun light facing the sun directly. Anything less than that (vertical mounting in a back-pack) will drastically reduce their power output. Think on the order of 80~90% less output.

Frankly, I think what you want to do would work to keep an ordinary cell phone or an ipod charged, but is probably not up to the task of keeping something like an ipad going.
posted by Long Way To Go at 8:45 AM on October 28, 2010

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