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Discussion Starter #1
I checked the voltage across the battery, using a digital voltmeter. I got a reading of 11.52 volts. The battery, a Bosch Premium, is four years old. Is it time to replace?
 

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Is that an overnight reading or after the car's been running? I would double check the alternator output and make sure it's 14+v when the car's running. If the alternator is good, I would just replace the battery being that we are going into the heart of winter.
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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11.5 volts is a pretty much dead battery. Normal for a full charge is around 12.5-12.6, with at least 12 being the minimum. With the engine running it should be 14v, give or take .5v.
 

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That is almost a depleted battery. I'd get it started and let it run for about 30-45 mins. See if the voltage comes back up. If it doesnt you most likely have a dead or dying cell. Cells carry 2.1v's a piece. Average battery life is 3-5 years.
 

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The way to know is to charge it for around 10 hours, then leave it overnight.

http://www.batterystuff.com/tutorial_battery.html#6

If the voltage is still low, replace it.

Be sure to charge the new one before you put it into use; it needs an equalizing charge; ~10 minutes 'gassing freely'.
 

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Yeah my car had a tired weak alt and a tired weak battery...new alt helped a bit, new motocraft battery fixed it for good, now running 14+ volts, when I first got the car it showed around 10 volts, sometimes less
 

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Also keep in mind that just because you have Voltage doesnt mean you are charging amps. Listen for a lazy crank or extended. That is a good sign of low amps. Best thing for you to do is get the voltage back up and jump it if need be and go to a shop and get the battery tested. If you have AAA or know someone with AAA they will come to your house and test the battery for you along with checking the starter Voltage and amps, Alternator Voltage and resistance,Draw test and battery numbers.
 

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Discussion Starter #9
Additional information:

Drove the car 90 miles yesterday. Today, checked voltage, 12.2volts. With the engine running, 14.44 volts.

Using a hydrometer, five of the six cells read 1175, one cell reads 1125.
 

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Discussion Starter #10
battery update

I went to an Interstate dealer, and I had the battery tested. According to the results, the battery and the charging system are OK.
 

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Was it a digital hydrometer (i.e. temperature correcting) or did you use one of those glass thermometer type ones?

The non-digital are calibrated at 60 degrees (almost all of them anyway), which if the electrolyte isn't at 60 degrees, you will need conversion tables to find the correct specific gravity. Also, you care more about cell voltage, not necessarily about specific gravity of the electrolyte. The SG may give you a piece of what you're looking for in terms of battery life for ALL cells. Unless you test each cell in terms of SG and voltage, you really don't know.

Put it on an equalize, like grog said, and see how long it holds. I got 9 years out of batteries in my 94 Bird and 99 Saab.

You can always take the battery to Sears or Farm and Fleet or something and they can test it for you, no charge.
 

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1 thing that always seems to get overlooked, is the level of the water in the battery....if the plates become dry, any part of them, they will start to damage rather quiclky....I'm sure there is some tech words that I could use...but I don't know em.. :D
 
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