Battery FAQ's

I didn't know that a bad battery could cause your car to stall and loose power on the highway until it happened to me last week in Reno.

The AAA tow guy convinced me it was the alternator as did the service station wrench who said, "we see this all the time." So I went along with their recommendations and paid the big bucks for a new alternator (ouch!) and went on my way thinking all was well.

The next morning the same thing happened on the freeway a few miles out of town and I was lucky enough to coast to the next exit where I called for the tow back to the Shell station that put in the new alternator. And again they insisted that it must have been a bad new alternator. Meanwhile, I suggested they try a new battery before replacing the alternator again.

With the new battery in place they were surprised to see it charging at 14.8V. They even did a load test on the car and they could not believe that my battery was the cause of all the problems.

After this experience I had to find out more about batteries when stumbled into this site:
http://nyquist.ee.ualberta.ca/~schmaus/batfaq.html

Cheers,

Joe


[This message has been edited by stlrj (edited 01-14-2001).]

Joe,

I never cease to be amazed at people who think they can diagnose problems without doing any testing! Low system Voltage can cause many different problems, but it can be caused by four DISTINCT, DIFFERENT PROBLEMS!!!

1. A deffective battery, typically with a shorted cell, or more than one!

2. A deffective alternator, such as an open stator, defective brushes, or blown diodes, or shorted diodes.

3. A defective Voltage regulator.

4. A short in the system.

Deciding which of these is the problem requires skills to make valid tests, troubleshooting skills to eliminate good components ... many so-called mechanics or technicians don't understand basic electricity, or testing, and SIMPLY MEMORIZE A FEW KNOWN FIXES!!!

I think you have recently encountered more than one 'tech' that falls into the above category!

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 01-14-2001).]

Thanks for the FAQ. Lots of great information and very timely.

I just bought a 6A charger last week. My battery had been sitting for several months. When I first hooked it up it read 40%. After a couple of hours it was up to 80% but I could hear the electrolyte boiling. I took it to the local "Batteries Plus" store where they load tested it and found no problems. I'm going to go back and follow the instructions in the FAQ to retest it and the alternator. It might also explain my low power problems.

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Greg
72 911S