Currently Being ModeratedMar 17, 2013 8:08 PM (in response to chelseacold)
Time to replace it.
You *can* *maybe* run on just wall power. But many operations still need battery to fully run.
Besides, old batteries can swell and leak chemicals.
Apple Store can tell you final cost, but I suspect it will be around $130. Battery is a "wear and tear" item that you may need to pay for.
Currently Being ModeratedMar 17, 2013 8:20 PM (in response to chelseacold)
The model 6,1 Late 2009 and the model 7,1 Mid 2010 use an A1331 battery. You can replace it yourself or have Apple do it for you. If you need it quickly make sure you order it from a U. S. seller. Orders from China can take two or three weeks.
Here's installation instructions. You'll need a Tri Wing Y1 screwdriver in addition to the usual #00 Phillips screwdriver.
You can keep using it with the power adapter until you get a new battery.