Plans for adding a general charger
Was planning to add some pictures of my parcel carrier, which I´ve used for the past two months but it’s too late in the day for taking good pictures – will be coming soon though 🙂
Instead I’ll tell about my plans for adding a general battery charger. As you probably know a hub dynamo adds drag even when not in use, so the best solution would be a spare back wheel and just change to the one with the dynamo when I’m going on a longer trip and will need it. I’ve been thinking about using a 6v hub dynamo and then connect it via a transformer that doubles the voltage to an old cigarette lighter from a car that I can mount on the bike, then any device that I might be needing could be put into that.
However, the tests I´ve been able to find (pilom.com and vintage bicycle quarterly) both shows that the power output is limited, because you dont want the voltage to get too high so it would burn out the lightbulbs or whatever you have attached to it. I want as much effect as possible though – a standard Nokia “in-the-wall”- charger is built for 34 W and the 6W output that you can get from the dynamos I´ve heard of isnt as high as I want it. Is it possible to avoid limiting effect and still keep the voltage below harmful levels? I don’t know, yet. I’ll keep on looking for an answer, any help is, as usual, highly appreciated.
Petter's HPV blog 
you might want to try just getting an external battery for your gizmos. they sell reasonably cheap external batteries with a standard usb out that will charge a cell phone three or four times or keep an iphone running GPS apps running for a whole day instead of three hours before needing to be recharged. unless you plan on spending days away from civilization this will probably handle most situations.
I guess it depends on what kind of smartphone you are using. Mine got a 4″ TFT display and with bad coverage out in the countryside and bright sunlight (autoadjusting for the screen brightness on) I can empty the battery in under 3 hours.
If one of those batteries can charge my phone 3 times, I need at least two to make it through two days..
Could still be worth it though, a hub dynamo isn’t completely weightless and it adds drag..