battery ?

has anyone ever heard of a battery having a dead cell and then turning on the defense mechanism of the computer so your car won't start? my stepson's
Hyundai accent wouldn't start and i got 12 volts at the battery and at the wiring harness to the coils. the coils and crankshaft position sensor were new. the dealer charged him $118.00 for the battery and now it runs ,where before we got no spark, even if i jumped it with a portable power pack. any thoughts? thanks
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stepson's
any
Yeah, I have a thought. $118 for a car batter is absurd! Tell your stepson he's got my sympathy for getting ripped off like that.
--

-Mike-
snipped-for-privacy@alltel.net
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my thoughts exactly. great dealer hey? no wonder i never take my cars in.
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Mike Marlow wrote:

Yes, if that was the battery alone that is a rip-off. If it was the total bill for diagnosis and replacement of the battery as well as the battery, then I'd say it wasn't unreasonable.
Matt
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its my observation that a good12 v battery is really more like almost 13 volts unloaded. Did it light the headlights brightly? Did it blow the hown loudly? ie Did it adequately power all the other stuff?.....anyways your kid will probably be more likely to get out a wrench and change it himself next time around...ps how old was the battery? pps were the terminals/cables clean and making good contact?...don't know why your portable unit didn't work. .

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wrote:

12 v is too low. It should be around 13.6V.
It's not a case of turning on a "defense mechanism", rather an issue of not haveing enough voltage to turn on the computer and other devices. I suspect the voltage would really drop when cranking so that even if there was enough power to see the dash and light some lights the voltage level would drop below the sensor and computer minimums during cranking.
BTW, price would not be that bad. Figure an hour labor plus the cost of the battery for diagnosis and installation. Dealers have to pay taxes and eat too.
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nothermark wrote:

Only if it is on a charger. A resting battery is more like 12.6V if it is in good shape and depending on temperature.
http://www.buchanan1.net/lead_acid.shtml
Matt
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wrote:

I don't think I have ever seen a good one run that low but my favorite source - http://www.batteryuniversity.com/partone-13.htm agrees with him. That is the minimum though. We always learned that lead acid wa 2.2 v / cell. That does seem more normal.
Either way 12 is too low but we don't know how well that was measured. By that I mean around 12 on an old mechical meter or 12.053 on a recently calibrated DVM. It's really too bad he didn't stop by somebody like Autozone and have it load tested before hitting the dealer. Testing under load is the only good test as it shows up bad internal connections as well as charge capacity.
Mark
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nothermark wrote:

Where did you learn that? I was always taught (I'm an EE) that 2.1V per cell was nominal for an LA cell.
Matt
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wrote:

E tech - I can't say where I learned it - it was too long ago. perhaps Navy, perhaps tech school, perhaps etc. Just out of curiosity I went out and checked the car - 12.69. Checked back to a couple of web sites. The only thing I can say now is none of the numbers match exactly. ;-) OTOH discussions like this get me to relearn old knowledge. It's good to check back on what I think I know every once in a while.
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