I just finished a 2 week tour of Ireland using the PedalCell and ridewithGPS for route finding. That is, I ran rwGPS for the entire time I was riding. I also took photos, did some location checking and routing with Google. In addition, at first, I kept the cellphone service and data on.
Here is my recent experience:
I stay indoors at night so always start the day with my iPhone fully charged or very close to it.
On the first day I rode 50 miles (80 kms) using the rwGPS and other apps running and kept the cellphone and data on, the phone steadily lost about 2% of power per mile. That meant that at the end of the day, my phone was almost dead and I had to turn off the cellphone services and data (go into airplane mode, which doesn't affect GPS) to get guided to the end of my route.
After that, I kept the phone in airplane mode for most of the day, only turning cellphone services when I wanted to check email, send message, make a phone call, access Google, etc. Again, this didn't affect GPS based apps.
On these days, I found the phone lost much less power and I usually ended the day with plenty left. Depending on the length of the ride, at 50% or more.
Note that I was touring in Ireland, which is hilly. On flat ground where you can go much faster, you might generate much more power. Though, I rarely unhooked the PedalCell.
I also rode in the rain a bit (thankfully not a lot!) and found that rain had zero effect on the PedalCell. Though, finding a rain-proof place for your phone and the PedalCell cord might be a challenge. I bought a water resistant top bar bag that worked very well.
While the PedalCell claims it can charge 2 devices at the same time, my testing suggested that this was more promise than reality. This is only possible if you are riding at speed and limits the amount of power the second device receives. I only charged my iPhone with the PedalCell.
You used the terms "devices" in your post. If you need to charge more than one device and will not have access to wall plugs for your entire trip, in my opinion, you will be hard pressed to do so. If you only need to keep and iPhone or a GPS device charged during the day, then the PedalCell will do the job.
I'm happy to respond to specific questions if you have any. Though, the people at PedalCell are very responsive to whatever queries you might have, often in a few minutes. Also, be sure that the bike you plan to put it on has the geometry to allow you to mount it properly. This is key as an improperly mounted PedalCell could be dangerous (should it slip and go into your spokes).
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