I know the WIFI cards suck tons of juice, which is why I think an internal WIFI would probably been a good idea for Sharp.
However, I am unsure but I think 1 hour of WIFI is on the low side. I think most people can achieve about 3 or 4 hours of WIFI time before needing a boost. However, my memory may be skewed because I ALWAYS used an external 4xAA pack whenever doing heavy Zaurus work (so to speak).
For example I can watch a 2 hour movie at 15fps (plenty for such a tiny screen), and good sound (in-sync) with an AA battery charger and barely even lose half my battery. And Movies do suck battery as well. Even worse than WIFI I think due to all the processing.
So my advice is see if there is any options for a different (lower-powered card), although Abicom is one of the best (depending on specific model of card...lots of posts about Ambicom CF WIFI card models...I don't use Ambicom, so I cannot say why).
I use a D-Link card and I was very happy and not sure of time usage, but an hour of WIFI (with just internal) would definably be easy. Beyond that I can't offer anything except that your battery might be a dud (is this a NEW battery?) or it could be SO new that you should really cycle it to full drain a few times, it may help a bit, but usually that is only needed for NIMH...but I have heard reports that it helps Lion that have been on "the shelf" for a while.
Replacement batteries and external are available on Ebay...one of the best sellers (by general consensus) for cheap Sharp accessories was a guy called PeakCloudy but not sure if he still sells on EBay (Note: I have no affiliation to him, except as a customer).