Vaio SR won't charge past 48% or 52%

For some reason my mom's VGN-SR240n seems to get "stuck" when charging. Recently, when I hover the mouse over the charge icon, it reports, "48% available (plugged in, charging)," but it just keeps reporting the same thing no matter how long I leave it plugged in.



I verified in the VAIO Control Center that "Battery Care Function" is *not* enabled, so the laptop *should* charge to 100%. I also switched "power plans," but that did not help.



I suspected that maybe it *is* in fact charging to 100% but only reporting a 48% charge. So I unplugged it and began playing videos on it. Interestingly, for about the first 15 minutes it continued to report 48% available, which signified to me that it had in fact charged up beyond the 48% it was reporting. Just when I was suspecting that it had in fact charged up to 100% and that I would therefore have to wait maybe an hour or so before it dipped below the reported 48%, it in fact started showing 47%, 46%, etc. So it seems to have been charged somewhat up above 48% but not all the way up to 100%.



I then removed the battery and powered on the laptop with no battery, using only the AC adapter. That worked fine. I then put the battery back on and let the laptop charge overnight without turning it on.



This morning I turned it on, and while plugged in it reports, "52% available (plugged in, charging)." It has reported the same thing for the past half hour while plugged in. Why 52% this time rather than 48%? And, more importantly, why not 100%?



Does anyone have any suggestions for how I can make this thing charge to 100%? Thank you in advance for your thoughts.