I think I'm experiencing a similar problem ...
And on my 15" AlBook, there's no such airport card slot ...
^^ Under that little cover with the four screws is your RAM.
I usually get about 3 - 3.5 hours with my Albook .. but that's if I'm really not doing anything other than surfing the web or coding or reading...
Playing music will drop the battery life considerably... movies even moreso, same goes for compiling (obviously).
I came here hoping to ask precisely about this kind of issue... But I think my situation is reversed.
My lower memory slot works perfectly. My upper memory, however, doesn't. I have a stick of Samsung ram (that came directly from my friend's Albook of the same model) and a stick of Micron ram...