Looking to purchase portable solar panel kit

Hello,

I couldn't find anything so I am posting.

Looking to buy a solar panel to keep my truck battery up to charge. I will periodically charge my Bose speaker, cell phone and lap top while camping in baja. What is the best way to figure out how much wattage I will need - 20 watt, 40 watt? Will likely just use clips to the Battery.

Any ideas, or recommendations are appreciated.

cheers
rg

 

I have a 100 watt Renogy panel, personally wouldnt want anything smaller. I connect it to my battery on my rig to help keep it charged while it's running my fridge but even still it cant keep up

 

http://www.expeditionportal.com/forum/forums/48-Power-Systems-12v-Solar-Gen