iPhone external battery recommendations
 

Smartphone gps apps drain battery life.:( I have gotten one to two extra hours of battery life using a Brookstone iPhone backup battery but am looking for a better option to use when I am using Map My ride. Any suggestions will be appreciated.

Pricey, but doable. On the plus side, you'll be upgrading your lighting in the process.

That works but the way I did it was like this.

1) Get a cheap car USB adapter - 1 port. Cost me a whole $4
2) Rewire the connector for deans (or whatever your favorite plug is)
3) Get a 12v power source. It could be a 3s Lipo, Lithium Ion. It could be 8 rechargable aa cells - they can hold a decent charge. Also you can use ordinary aa batteries as a bail out if you run out and really need them. Attach the usb adapter to your phone with the cord and you have... a charger. :) The batteries will probably cost around $20-$40 but, it will run your phone for 6-8 hours.

Now if you overkill with a large 12v battery like a 5ooomah lipo (be sure to get one with the discharge preventer built in!) You can run yuor phone for a loooonnnngggggg time.

My first setup something like mentioned above.

http://inlinethumb05.webshots.com/18...600x600Q85.jpg

My new setup http://www.tekkeon.com/productcart/p...&idproduct=194

http://inlinethumb58.webshots.com/48...600x600Q85.jpg

My day to day battery extender is a Mophie case.

http://www.mophie.com/

I put a 9ah motorcycle battery in the trunk at the back of the bike for fun.... 9 hours later it had used 2000mah. I'd bet you could run that for days without charging on a tour. Sadly the battery weights almost 3kg and its more weight than I'm willing to carry. Just got some Energizer 2450mah batteries. Going to see how long they last. At best estimate from the 1600mah lipo that died at 6 hours I would say 6-8 hours before the voltage dips too low to run the usb adapter.

I'm also using a morphie case over my iPhone which adds an extra 2500 mAh to the mix.
However, I'm also using twin 5,600Ah 12V Lipo battery packs to run my lights and as suggested by krobinson - its easy to add an adapter to tap into that for extended iPhone use too.

What I learned with building the first iPhone charger shown above using 8AA batteries to get a 12v supply and then using a car adapter to regulate current and voltage and the iPhone 3 and 4.

Car chargers are not all equal in their design but basically cars when running show slightly above 14v and at least 12v when not running. The chargers are designed around 12 to 25v. The iPhone 3 was less critical than the 4 with several chargers I tried to low voltage input. Around 9v input was when I would get error messages from the phone. When I went to the i4 is when I started looking for a better setup and found the second one shown. It had the advantage of using re-charge batteries and also doubled as a charger with pass thru that lets you charge batteries and phone at the same time. The output charging amps is too low to do both the phone and the Mophie at the same time though. It works but got a little warmer than I liked and in reading the specs I saw I was pushing the limits. The fact it takes both types of batteries (throwaways and re-charge) makes it a nice fit for touring. I normally use it with re-charge and in a pinch can find throwaways everywhere. An added bonus is it works great with a little USB light also, handy when patching a tube in the dark or to light up a tent.

My Mophie is the newer higher capacity but not the weather resistant one. I don’t care to view my phone anymore like the setup I show in the first photo. I keep it handy in my bar bag but don’t need it in my vision all the time.

Plenty of battery packs with usb adapters designed for phones and tablets are available at retail, from makers like Trent.

And the packs mentioned from makers like Mophie give you an all-in-one solution, but may interfere if you're mounting the phone on the handlebar. Are there custom bike mounts for phones that include a battery pack?

Yes (at least for the iPhone).

http://www.wahoofitness.com/

http://www.ibikesports.com/

How about you invest in a dedicated GPS like a garmin? I don't see the point in using a phone as a GPS while cycling? I like my 4S to make phone calls and my garmin to do the gps.

You have to buy two (expensive) devices when one can suffice.

The major reason not to use a smartphone is the battery duration. (Another reason might be the water resistance/durability.)