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Old 06-26-2011, 04:10 PM
Charter Member
Join Date: Feb 2003
Location: Chicagoland(West Burbs)
Posts: 767
Can an car alternator put out too much power and ruin a battery?

After taking my battery to the auto parts store to have it recharged, I found out it was fried. After the guy looked at it he told me my alternator was putting out too much power and I might need to have it replaced. This was after making the observation that the sides of the battery where solid and bulging. I have never heard of this. My doubts come from the fact that the same battery and alternator have been in the car for 2 years. Is it possible my alternator fried my battery?
Old 06-26-2011, 04:29 PM
Join Date: Apr 1999
Location: Wisconsin USA
Posts: 16,843
You can destroy the battery if the alternator overcharges the battery. This has to do with the regulation circuit going bad.
Old 06-26-2011, 04:47 PM
Join Date: Mar 2002
Location: KCMO
Posts: 11,123
Perhaps the most common external causes of premature car battery failure are (long term) undercharging and overcharging. I wouldn't use the term "power;" I think it's more accurate to say the alternator delivered excessive voltage. While the battery's condition may be a clue to this, I would certainly measure the charging voltage with a test meter before condemning the alternator.
Old 06-26-2011, 05:02 PM
Charter Member
Join Date: Aug 1999
Posts: 16,451
Power and voltage are interrelated. If the regulator circuit puts out more amps than the battery can absorb the voltage will spike due to the internal resistance of the battery. Voltage is easier to measure.
This excessive can and will cause gassing and boiling of the electrolyte and can destroy it.
We had a car in last week with this problem. Charging at 18V and had boiled away most of the electrolyte. New alternator and battery was the fix.
Remember this motto to live by: Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather one should aim to skid in sideways, chocolate in one hand, glass of Scotch in the other, your body thoroughly used up, totally worn out and screaming "WOO HOO! Man, what a ride!"
Old 06-26-2011, 09:36 PM
Join Date: May 2000
Posts: 509
Back in the day, voltage regulators were seperate from generators and they could cause your problem. Since I have no idea how old your car is, it's hard to say, but if the internal voltage regulator went bad, it could cause the problem.
Old 06-26-2011, 10:11 PM
Join Date: Dec 2007
Posts: 114
Mini Cooper or Range Rover?

When an auto battery starts going bad, the car's computer can increase the voltage put out by the alternator in an effort to compensate. Some cars require a computer scan and reprogramming to force the voltage back down after the battery is replaced.
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