On one of my cars the battery always reads what would seem to be a bit low. The voltage would be about 12.40-43 after one or two days. This battery always read about the same from day one and I figured it wouldn't be a good battery. However, the battery was purchased new in 1998 at Autozone so it has been one of the best battery's that I've ever owned.

In my van, the battery would read about 12.6 which would seem more normal.

I'd say if you are getting a reading below 12.4 that you should be watching it even though in my example 12.4 seems to be normal after 6 years now.

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JD