Extremely cheap solar 18w solar panel. Worth it?

[Dagrip]

Sunsei 18 Watt Solar Panel and Controller $99.99 + $5 shipping
1 Sunsei SE-1200 18 Watt Solar Charger
1 Sunsei CC25000 25 Amp Charge Controller

http://sellout.woot.com/

We are about to make our first adventure to a music festival where we will have no power available to us for 5 days. We will be purchasing a Honda eu2000i but plan on using it sparingly due to noise and fuel availabitly. I came across this solar panel this morning and I am wondering if it would help keep our battery charged at all during the days or if it is just too small of a cell to even mess with.

Thoughts?

Scott