Q: Car won't start, I think it's the battery but I'm not sure.

Last night I tried to start my car but it wouldn't turnover. I assumed it was the battery so I called a friend for a jumpstart. He accidentally switched the red and the black cables when he put them on my battery and his car died, so we called another friend and he put it on correctly but the car still wouldn't start. It makes a series of clicking noises when you try to start it and the radio and the inside lights flicker but they don't stay on. We checked the relay and it was fine, and we don't think there's anything wrong with the starter because it makes a series of clicking noises when you try to start it. Does that mean I just have to replace the battery?

My car has 60000 miles.
My car has an automatic transmission.