Reality Check : Solar Charging an iPhone

iPhones, Blackberries, and other smartphones are a common solar charging question. So here is a summary of what you need to know to avoid frustration and choose the solar charger that will do the job for you.

USB Port Compatibility

The first thing you need to know is that as smartphones have evolved, their power requirements seem to be getting fussier & fussier. An iPhone has become the laptop computer of the USB set. So, while the iPhone and others are still "USB devices", they need specific performance from the USB ports they connect to. Anyone with an iPhone 3 or iPhone 4 will be aware of this issue. Not every USB port is acceptable to an iPhone. I'm sure the iPhone 5 will be just as particular. An iPhone requires a full-function USB port, with specific characteristics, so it is important to choose only those solar chargers that specifically state that their USB port is Apple iPhone compatible. I try to test every USB port in our catalog to determine if it is Apple-compatible, and have noted the results on each web pages.
Beware of cheap chargers... if it doesn't say iPhone compatible, it won't be

USB Port Power Output

As iPhones have evolved, their minimum power requirements have increased. No longer will an iPhone accept a low-power USB port, even if it was once deemed Apple-Compatible. This means you need to choose a solar charger that is capable of at least 500mA output. Check the solar charger's specifications to know for sure.
What this means is that for a solar panel to be able to charge an iPhone directly, it has to be producing at least 2.5 Watts for even the smallest amount of charge to flow. The alternative is to store solar power in a battery pack that can in turn deliver what an iPhone is wanting. This is almost always the preferred solution, as this frees you from moment-to-moment solar conditions.
Special Note: if your iPhone is 'Off' it's power requirements are lower. But 'Off' is not usually the way people use an iPhone.
Beware of cheap chargers... they often lack the output power to handle iPhones

iPhone Battery Capacity

The iPhone 4 & 5 are similar in battery capacity, at just over 5 Watt-Hours (1400mAHr @ 3.7V). Given losses in the charging process, it will take approx 6.5 Watt-Hours to fully charge a current model iPhone.
What does this mean?
I'll hide the math & suggest that if you drain your iPhone battery easily in a day, you will need a solar charger of at least 2 Watts, and have it exposed to sunlight for most of the day (summer, for most North American locations).
But, like I said in the previous section, the iPhone will likely ignore panels producing less than 2.5 Watts, so you need to use a solar storage battery pack between the panel & the iPhone.
Below are links to several popular solar chargers for the iPhone, along with their performance.
Beware of cheap chargers... they use poor-grade battery cells

iPhone Connection to Solar

This part is easy.
Use the USB cable that came with your iPhone. The iPhone 5 has a new connector, so your old sync cable will not work with it.

Recommended All-In-One Solutions (for all iPhone models)...

#1 : Voltaic Fuse
4 Watts in peak sun (up to 2 full iPhones per summer day)
11 Watt-Hour on-board storage (almost 2 full iPhones)
Easily attached to backpacks etc
Click here to see the Fuse

#2 : Voltaic Amp
4 Watts in peak sun (2 Watts per side) (up to 2 full iPhones per summer day)
11 Watt-Hour on-board storage (almost 2 full iPhones)
Handy zipper case format
Click here to see the Amp

#3 : PowerFilm USB+AA
1.4 Watts in full sun (approx 75% of a full iPhone per summer day)
5.75 Watt-Hour on-board storage (approx 75% of a full iPhone)
Lightweight, sensitive in shade/overcast, uses/charges AA rechargeable batteries
Click here to see the Powerfilm

#4 : Brunton Restore
1 Watt in peak sun (approx 50% of an iPhone per summer day)
8 Watt-Hour on-board storage (slightly more than 1 full iPhone)
Rugged pocket format, easily attached to packs
Click here to see the Restore

#5 : Brunton Freedom
0.5 Watt in peak sun (approx 25% of an iPhone per summer day)
8 Watt-Hour on-board storage (slightly more than 1 full iPhone)
Rugged pocket format, easily attached to packs, great back-up battery
Click here to see the Freedom

Beyond The iPhone

Bundled solutions, comprised of a larger USB solar panel like the Brunton Explorer or Goal Zero Nomad 7 can be combined with a USB storage battery like the Voltaic V11, V39, Brunton ReSync, Inspire, or Guide10 Plus, to create your own higher power USB solar station. Such systems can support tablets & iPads if the storage battery says it can, but that is a topic for an upcoming post.

Let me know your questions or comments!