Cheers for the input folks,I always carry two old Nokia's (one in the car and another in my rucksack).As you say,the batteries seem to last far longer than the modern devices.
I've also knocked together another charging device from a battery pack off a CB radio I bought using a (£1) 12v cigarette usb charger and I'm planning on using it with a multi usb (it might work
).At the minute it charges my iPhone at a rate of 2% per minute so it'd take about 50mins to charge fully from flat.
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The contraption using TEG's was really only a little project to see if I could knock something together to charge my devices if all else failed and all I had was a stream and flint and steel but sadly it's too heavy to lug about and the chances of that are slim to none
I'll grab one of them powerbank devices too (just as a back up),hopefully it'll hold a charge and won't need charging if left for a few days without use and if it isn't too heavy it can stay in my camping kit permanent.