I have been looking around the interwebs for a few weeks, trying to find a complete (and hopefully accurate) package of information on the topic of staying powered up on tour. It's a perfect topic for Adventure Cycling's researchers and writers to tackle.
Here's what I'm finding:
1. The devices (we think we must have) on our bikes have small built-in batteries and can deplete their energy supplies quickly due to usage and possibly cold weather.
2. Some of these devices, such as a smartphone in GPS mode, require supplementary energy supply in the form of energy generation or an attached auxiliary power pack or they only last a few hours.
3. Devices and auxiliary power packs can be deeply discharged during the day's riding (or riding out a storm in a tent) and must be thoroughly recharged.
4. You have several options for the energy to recharge including AC power, hand-cranked generation, bike-powered generation, solar, secondary battery storage or fuel cells and other energy sources.
5. There is a direct correlation between the mass and cost of these auxiliary charging and generation systems and their ease of use which includes storage capacity, ruggedness and other factors.
6. The marketplace is crowded with a range of low- to high-quality products being sold to a largely uninformed public.
REI recently had a good discount on a product from Goal Zero, a 3.5 amp solar panel and a battery pack that holds 4-AAs. You can charge the pack from almost anything and you can pull energy from it to recharge your phone or other devices or you can use the AAs. MMy experiments so far indicate I can deplete the Goal Zero pack charging my iPhone to a total of 100% (one charge from 40-100% and one charge from 60-100%). The solar pack will NOT power anything, simply doesn't have the energy output, it's not large enough, but it will recharge the battery pack from 10% to 100% capacity in 6-8 hours of FULL sunlight.
So if I want to run the iPhone on the bike in mapping/GPS mode, I will need at least two of these auxiliary batter packs. One to carry on the bike and one to have recharging on the back of the bike or in camp.
More to come later as the season starts up.