What do you guys do to charge your mobiles when you're a few days away from being able to plug your charger into the wall? Obviously, part of the attraction to the outdoorsy lifestyle is getting away from all that, but even so sometimes a phone can be very handy. I've heard about solar chargers, but with the amount of sun we've got at present, I'm not sure that they're a very viable option. Are they? Or are there any manual chargers (wind up for example) that you've had good experience with? Or would it be better just to have a power bank in my rucksack?