Battery Indicator Light

[jhoffman80]

I have a 2000 mustang v6. Three days ago the battery indicator light came on and the dash lights dimmed when i went over 2k rpm. As I slowed down and the rpm went down, the battery light went off. Last evening I drove to the store and the same things were happening. When I left the store and attempted to start the car, it wouldn't start. I went to the auto store next door and they had a jumper pack so I was able to get it started. They tested the alternater and it was ok. They tested the battery and within a few minutes the charge had dropped to about 4 and was still dropping. Assuming this was the problem I purchased a new battery and the car started right up. Today I woke up and began driving to work. Just like before, as I went over 2k rpm's the battery indicator light came on.

Has anyone experienced this sort of problem before? Does anyone have any suggestions as to what might be the problem, or some things to test out?

Thanks for your help.