So, i got my car started. I just disconnected the battery, and connected it back after like half an hour, and it fired on the first run. But! After running for a while, when I hit the breaks, sometimes, the radio would go off. Sometimes I don't even have to hit the breaks for the radio to turn off. Another thing I noticed is that when I took off my seatbelt, and looked at the light by the rearview mirror, and hit my breaks, it dims like half way, and then comes back. Can this be a sign of a bad battery? I don't think it's the alternator, bcuz the car wouldn't turn over at all.