I have a 2.16GHz C2D MBP and I bought a new battery off ebay some time ago, and although it came with a dented corner, I kept it and started to use it. I have just started using the MBP again and it is not recognising the battery. I have a little battery icon with an 'x' in it, and in system profiler it says battery is not installed. I've also tried a 2nd battery and that's doing the same. However, with the 2nd battery, when I unplugged the PSU, the MBP stayed on for a short time (I think down to the lack of charge in the battery). Does anyone have any ideas?