Ok so today my car started fine no issues . I have a 1500watt Rms alpine/Memphis sound system and I was bumping it. Out of no where amp started turning off. Thought I blew the amp or something had got loose making it go to protection mode. I pulled over turned the car off checked the system. Everything seemed fine. Hopped In The car and it barely started(cranked very slow) and my power steering was stiff. Drove around a few minutes and the power steering came back and car turned on fine after that. Took it to AutoZone. Guy seemed kind of off but he said the battery is very low but its showing good and he can't test the alternator without the battery being charged. I went home charged it up. Took it back said alternator and battery are fine. Sound system played fine again for 15-20mjns and shut off. Parked the car checked the volts of the battery and it was 12.39 car off. When I turned it on the volts started raising but veryyy slowly. Went to I think 12.7 in about 10-20 seconds. I've measured my voltage before and I remember it being 13.8 as soon as I turned the car on. But car starts fine again and Power steering isn't stuff. No weird lights. No battery light. It's late so I'm going to go to pepboys but can anyone chime in as I am confused to how everything showed good. Is the alternator just getting weak and the amp is pushing it to it's limit so it's showing symptoms? Or can it be a bad battery. Hopefully pepboys can test it and tell me a answer to what's wrong and not just say everything is fine. Any help or ideas would be appreciated. My cars at 82k miles right now and I know these alternators don't last forever. Plus the sound system pushing it to it's limit might have made it failed. But I don't want to throw hours of my time in 100 degree weather and $200 at something before I make sure %100 that's the issue.

 

I don't have any suspects outside of the battery itself. Most likely a dead cell. What's it's date code?

Your symptoms sound a lot like when I go to start ours when it's negative-***** degrees out and the battery's already past the point where I shoulda hooked up the trickle charger.