Today I had a bit of car trouble where the culprit turned out to be the battery. I had driven my car just 5 minutes earlier without issue, but upon attempting to crank the vehicle it made a final effort at turning over and abruptly stopped, as if the battery leads were suddenly removed and all power was cut-off. After a bit of troubleshooting I solved the problem, but several questions came to mind.
I measured the open-circuit voltage to be 12V, but when the battery was wired-in (vehicle remained off with key removed) the same test measured only 8-9V. I am not sure exactly what kind of load remains on a car battery when the vehicle is off, but there certainly was a significant voltage difference. So
- What causes a battery cell to die?
- Are there symptoms of a dying battery or do they often quit as this one did (immediately, like a switch was flipped)?
- The behavior described above leads me to believe the battery was working fine right up until something caused it to abruptly stop working. What "something" might this be?
- If a cell was indeed "dead" as I was told, why did I measure these voltages? I would expect lower voltages if an entire cell was not working properly.