Charging devices on expeditions can be challenging. Solar devices can work well while 'in place', but are difficult to manage while moving and can take a long time for the device to charge. If you move during the day, you may find that the available solar power is limited to a short time, before and after hiking - and is insufficient to charge your equipment.
Another option is a small pre-charged battery pack. If you are looking for way to quickly charge your smartphones & USB devices, I've found no better quality and value than the mophie juice pack powerstation® mini. This small pack measures 1.92 in x 3.64 in x 0.53 in and weighs less than three ounces.
Battery capacity is 2500mAh which will charge my i-Phone 5s twice. Each charge takes approximately 25 minutes.
The battery pack can be recharged via a USB port and is designed for 100 charge cycles.
Currently the price is $59 and is available at www.mophie.com