Battery problem please help?

I have a Hp G60t-200 CTO laptop and have had it for about 1 1/2 years now. Recently the 6 cell battery went out on me and only held a 40% capacity. I recently bought a 12 cell battery on ebay from silicon electronics and the battery seems to be experiencing the same problem except it says its capacity is 60%. Could anther part of my computer be the problem to this? I am running Windows 7 ultimate and using the power saver mode so the computer doesn't drain energy.