[DML] Re: question about battery life

["David Teitelbaum" <jtrealty@xxxxxxxxxxx>]

Doing a cranking test (using the starter as a load test) is a quick
and "dirty" test. It is dependant on too many variables though like a
bad starter, dirty or loose connections, low compression, to name a
few. The light test is a little better but can be meaningless if you
take the results from another kind of car and compare them to the
Delorean. It is not difficult to have a battery load tested. First
charge it up slowly ( 2-5 amps for 2 days). Next take it to Sears or
any large chain and they will test it on a load tester for free. They
do this to try to sell you a new battery. In most cases if you bring
an old battery in and suspect it to be bad it probably is. Don't waste
testing anything over 5 years old. The "dirty little secret" in
batteries is that although you can still use a battery after it is 5
years old it generally has less than 50% of it's life left. This means
there is no reserve and should be replaced. A battery cannot be
properly load tested if it is less than 1/2 charged or has less than
50% capacity. Batteries in cars that are not used regularly age even
faster because of the deeper discharge cycles they see by usually
being allowed to go dead over the winter for extended periods of time.
I keep batteries on my cars healthy by removing them from the cars,
placing on a wooden surface, and charging them with a trickle (float)
charger 1 day every month when the car is not in use. Even with that
care 5-6 years is pushing it. An alternator that either doesn't keep a
battery fully charged or one that overcharges a battery will kill the
battery faster. A little known fact is that you can have an alternator
with a blown diode or 2 that still charges the battery. This is very
bad though because not only is the alternator not able to fully charge
the battery but it is now impressing an A/C voltage on the battery and
that will kill the battery quicker than sh-t. It is just good practice
to check the ENTIRE charging system when you change a battery so you
know the new battery will get to live a long time. 
David Teitelbaum
vin 10757



-- In dmcnews@xxxxxxxxxxxxxxx, "John Hervey" <john@xxxx> wrote:
> Dave, Using the starter as a load is smart way of checking the
battery. Here
> is some additional information from a local GM expert that writes
the books
> on battery and charging systems and teaches around the country.
> I took his 1/2 day course and it was wonderful.
> 





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