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

 

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.

 

my thoughts exactly. great dealer hey? no wonder i never take my cars in.

 

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.
..

 

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.

 

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

 

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

 

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

 

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

 

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.