Car battery question

My battery is staying fully charged but seems like it has an internal short if that is possible. The car plays dead sometimes. My post and clamps are very clean. Clamps are nice and tight. When the car is
acting totally dead, if I tap on the positive post, it comes back to life. The battery has warranty left so I can return it, just not sure what to say is wrong with it.
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On Tue, 3 Aug 2010 15:16:37 -0700 (PDT), " snipped-for-privacy@gmail.com"

You have one of 2 problems. Either there is a problem with the clamp to the pos post (take it off and clean it) or you have an intermittent OPEN (not short) in the battery.
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In the last 6 yrs. I've been through FOUR batteries for the same problem. 3 where auto zone and one diehard. Internal connector failure seems to be a common problem today, Must be the less lead content of these made in Mexico batteries. Rookies behind the counter try to play the it checks OK game when you bring it in for a warranty trade as it is a intermittent internal connector failure. My third AZ battery was on a $60 prorate so I went the DieHard route and that one failed in 10 months the same way. An no my Sable is not vibration prone off roader........

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Did you check the output voltage of the alternator?
Batteries seems so good these days I hardly ever buy one. Maybe you should get an Interstate or Motorcraft battery.
Ed

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Alternator is fine, it was wack the top of the battery and the lights would come on and cranked right up. Just like the movies when a UFO flies over you. Dead, wack, On . It could go days until it happened again in all the cases. Never a alt. light or any other sign of a problem until you hop in one time and it's a no start. Could happen on a morning start up or a restart. I think the Sears and AZ batteries may be made by Johnson Controls but a buddy of mine had a Interstate do the same thing to him.
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You are correct. At least the Diehards are made by Johnson Controls as are the Interstate batteries. Sure sounds like an internal design or manufacturing problem. DaveD

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On Wed, 4 Aug 2010 08:40:08 -0400, "C. E. White"

Interstate Megatron is my recommendation as well. I sincerely doubt the charging voltage has ANYTHING to do with the problem, however.

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