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I have an HTC Hero, which is a great phone, but the battery life is pretty poor if I'm using the GPS and music player on it as well. The phone uses a mini-USB connection for charging, and I have a Powermonkey portable charger just in case my phone runs out of juice.

But for longer rides, the extra charge and a half I get from the Powermonkey might not be enough - what other good options do I have? Either to charge the phone, or the Powermonkey, when cycling.

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is the Powermonkey just a toy? I pretty much broke the heads when I tried it. Felt it too unreliable for my use. And the extra energy did not last very long, more annoyance to me to carry it. –  user652 Mar 25 '11 at 16:28
    
I think I'd first look for a solar charger, and attach it to a rear rack. Would only consider a dynamo charger if I already had the dynamo. –  Daniel R Hicks Feb 26 '13 at 16:07
    
As Wilka is from England, I'd imagine a solar charger wouldn't normally charge as fast as normal cell standby used it up. –  James Bradbury Mar 12 '13 at 15:07
    
Using a phone as a GPS really eats up the battery life (especially if you leave the screen on for a long time), depending on what you use the GPS for maybe it'd be better to get a dedicated cycling GPS ($120 - $500, depending on features), which will let you conserve the phone batteries -- using my phone as an MP3 player with the screen off makes little difference in battery life. –  Johnny May 17 '13 at 19:34
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8 Answers 8

Three options that I know of:

  1. AA cell phone charger (which you're already using) -- uses 2 or 4 AA's to recharge your gadgets. I use an Energizer model to charge my GPS for rides over 12 hours. Of course you need to carry enough batteries for the length of your ride.
  2. Solar charger -- can be mounted on a handlebar bag, a rear rack or hanging from your pack and typically has mini-USB connections for cell phones etc. No batteries required but won't help much on a rainy day. I've seen a variety of these at local outdoors shops.
  3. Dynamo hub charger -- this is probably the most expensive option, especially if you don't already have a dynamo hub. I'd like one of these (already have the hub) but the AA charger has been fine so far.
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It may be possible depending on your ingenuity to modify a Minty Boost (see my post) to accommodate all three of these methods of charging. A trawl around the internet might (or a visit to the forums on ladyada: forums.adafruit.com ) might turn up something. –  Amos Sep 3 '10 at 11:02
    
A good dynamo add on is the plug II by supernova. It gives you a usb port on your stem. h1987995.stratoserver.net/magento/… –  Benzo Feb 26 '13 at 15:22
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I have a portable cell phone charger that uses 18650 lithium batteries. It works great as a backup battery for my phone. These batteries are much better suited for charging cell phones than AA batteries. –  Kibbee Feb 26 '13 at 16:53
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I have a HTC Hero which I charge using one of Ladyada's Minty Boosts (v2), when it gets caught short. This uses 2 AA batteries (which could very well be pre-charged rechargeables) to charge the phone (2 AAs give me between 20% and 30% of a full charge in about 30 minutes). I don't tend to charge using it while I'm riding, as it gets rather hot, and I'm not convinced my soldering is up to the job.

On the internet there are various instructions to modify Minty Boosts to run off solar power but on Instructables there's also a modification to run this off a bike dynamo.

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-1 for disposable batteries. Costly and environmentally ugly. –  Carey Gregory May 19 '13 at 16:37
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check out

http://www.wired.com/gadgetlab/2010/06/nokia-announces-bike-powered-phone-charger

or you can go crazy and get a dynamo front hub and a charger from busch and Muller (Germany). this will cost you a pretty penny.

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There is this company that sells bike powered phone charger kits. The price is very reasonable. I think this one may be suitable for your HTC because my husband has an HTC Incredible. http://www.bike2power.com/smartphone-bicycle-charger-kit.html. Not sure if they would ship to UK.

I got the kit for his b-day because he also complained about the battery life. He uses stats app when he rides, and the battery would be dead in 45 min. I looked at reecharge as well but it was too expensive and kind of complicated.

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Probably the easiest way to fix your problem is to reduce the amount of power the GPS on your phone is using. By default, most GPS tracking programs eat up an enormous amount of battery because they default to maximum-accuracy settings. However, if you're going on long enough bike rides that you are worrying about battery life, you can probably afford to turn down these settings.

The way to do this is different with each of the different tracking apps, so I can't tell you exactly how to fix this, but if you dig around in the settings for a while you should find something. I know that the two apps I've used (Runtastic and My Tracks) have both allowed me to do this.

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I've found that doing that results in very poor accuracy. At least with the app I use (CardioTrainer) distance traveled can be off by 5%, which is really quite a bit (1 mile/km in 20). –  Carey Gregory May 18 '13 at 15:52
    
In my experience, reducing the GPS sample rate doesn't affect the overall distance very much. What it does is makes it so that your path might show up say 20 yards to the left of where you actually went, but still parallel. Most programs have averaging of data points and trajectories of some kind, and should still work just fine with sampling rate turned down. –  Gwenn May 19 '13 at 1:38
    
Errors in location from a low sampling rate are going to be random and equal in all directions, so errors in left-vs-right will also be seen in forward-vs-backward, and those errors will affect the calculated distance. And at least with the app I use, they definitely are. Like I said, I consistently observed about a 5% error on distances using the low sampling rate. –  Carey Gregory May 19 '13 at 16:39
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You might look at just upgrading your current approach—a lithium battery based cell phone charger (like the popular New Trent ones) generally go a lot further than AA based ones.

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+1 for a rechargeable solution. Using disposable batteries is a hideous solution, both in terms of financial cost and environmental cost. –  Carey Gregory May 19 '13 at 16:35
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Joke answer, but I can't resist.

How can I charge my phone while cycling?

Leave it on your desk, plugged into the wall. :)

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This is funny, but it might be better as a comment than as an answer. –  amcnabb Feb 26 '13 at 20:01
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There's a project on Kick Starter that looks like exactly what you're looking for: The Siva Cycle Atom

The funding ends May 23rd 2013, and they should start shipping towards the end of 2013. So if you miss the window to be a Kick Starter backer, you should be able to pick one up directly form them around then.

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