Depends on your game plan for recharging batteries, IMHO the best route is with a fold able solar recharger with 20W or greater will give you allot options when on the move. I have upgraded my 20W solar cells with a 40W military one off of e-bay recently and have increased my electronics options. Solar cells let the sun do the work for you on sunny days of course and lets you spend more time doing other things. I have found allot of things the cells can do and the list keeps growing.
The cells can give you:
1. Fire
2. Navigation
3. Communication for emergency's or what have you
4. Water purification
5. Shelter in a stretch (The cell I have can act like a blanket or tarp and is waterproof)
6. Recharging batteries
7. Fans for cooling
8. Music,weather and TV if needed
9. Light
10. The list goes on and on

Anyway here's a 12v CR123 chargers that I use to recharge my steripen batteries. E-bay has some good deals on solar cells but these are fold able and add weight. If you are going ultra light then Polak187's solo would be more in that area. It all depends on what your game plan is. Mine has been built around long term use.

http://www.all-battery.com/index.asp?PageAction=VIEWCATS&Category=34

http://search.ebay.com/_W0QQsassZvitabon

http://search.ebay.com/foldable-solar_W0QQ_trksidZm37QQfromZR40