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Jfrahm Jfrahm is online now
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Join Date: Oct 2002
Location: Boulder, CO
Posts: 1,206
Over 13v is a surface charge that will dissipate. Disconnected, it might stick around for a couple days or only a few minutes. When it's gone you should see something like 12.8v for a pretty new battery or 12.6 for one a couple years old.
The speed of the loss of the surface charge depends on the internal resistance of the battery.

You can also use a light bulb or hook up the car and open the door for a few seconds to dissipate the surface charge so you can see the real state of your battery. Which sounds fine.
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Old 09-24-2025, 08:25 AM
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