Yes, by any chance have you gotten an extended battery? I am looking at a 6600 mAh or a 7800 mAh battery and am worried about having a battery that is too thick. I can't seem to find any side views of the computer with batteries attached to them.
I found a great battery program that will work with any laptop, not just the Acer Aspire One.
http://majorgeeks.com/Notebook_BatteryInfo_d4995.html