I have one of these:

http://www.solio.com/charger/explore...magnesium.html

and one of these

http://www.apc.com/resource/include/...base_sku=UPB10

The Solio will generally charge my Edge 705 twice before needing recharged. I have not charged by 705 with the APC but I did use it on my 305 and it would give me 1.25 to 1.5 charges.

The Solio can charge in one day IF it is in direct sunlight for the entire day. So this is a valid concern however since it holds two plus days worth of power it may still work for a multi day trip.

Prices:
APC $70 +/-
Solio $175 +/-