My Impala has been running (and starting) with no problems. Today, I tried to start the car and things started "popping" all round, the lights etc sagged, and I quit trying. I checked the battery voltage (about 12.5 V), and tried again. The voltage sagged to about 8, the popping went on again. I figured that the low voltage caused the computer to do strange things (the popping), so I checked the battery water level. One cell was quite low, so I filled it. (BTW, this is a two-year-old battery). I charged the battery to full charge (6 amps for about 2 hours), and tried again. The car started fine, over several attempts, and I am now monitoring the battery voltage. For a while, I was sure that I had a starter problem, but now I'm not so sure. So here are my questions: could a low water level in one cell cause a battery to act like this? Could a low or fluctuating battery voltage cause the "popping" What else could be wrong?
TIA for any help. I've asked for help on this group several times in the past, and have never been disappointed.
Jim Thomas