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Old 02-27-2005, 07:45 PM
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Join Date: Jan 2003
Location: USA
Posts: 699
What's your car battery's voltage after resting for 2 days.

If you leave your car off for 2 days (a weekend) without driving it, what's the average voltage of your battery after 2 days?

I also assume that your car has an alarm system and/or clock that consumes between 50 mA to 200 mA.



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Old 02-27-2005, 08:17 PM
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If everything is okay it should not change, but that is not a valid test of anything. Start by seeing that you have about 13.5 to 14.5 volts across the battery when you rev the engine up. If you do and the battery is draining anyway, you need to put an ammeter in series with one of the battery cables and see if there is a drain. The ammeter should not read over about 100 milliAmps.

If you have charge voltage and no excessive drain, have the battery load tested. They will do this free most places that sell batteries like Sears.

If you did NOT have 13.5 to 14.5 volts with engine running the problem is probably the alternator. Pull and inspect the brush pack. If the brushes are worn down short then replace it.

Hope this helps,
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Old 03-05-2005, 10:15 PM
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Join Date: Mar 2003
Location: Oklahoma/Missouri
Posts: 74
Originally Posted by ericnguyen
If you leave your car off for 2 days (a weekend) without driving it, what's the average voltage of your battery after 2 days?

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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