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Old 10-05-2002, 10:30 PM
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Battery or Charging System Problem?

I noticed it just didn't seem to have the usual exciting 1st crank start over the past week. Was planning to go out this past Friday night and noticed an ever so slight strain in starting. Pushed it 3 X just to test it and after the 3rd attempt the interior light dimmed just enough to give me cause not to take it out.

The next moring went to start and only lights on the dash came on, no cranking power.

Lifted the hood and checked the battery for acid. DRY......I never checked this before myself. I thought it was always done during normal routine trip for service. (NOT).

Refilled the battery with deminertalized water and put the battery charger on 2 amps for 6 hours.

Car started right up. Moved it out of the garage and came back 8 hours later and DEAD, dim interior light & no crank.

Jumpered it and first crank and it started and bright lights.

I've had the car for 3 years and never checked the battery level before. (My mistake & oversight). I don't know how old the battery is but it still looks new today. It's a MB battery.

Any suggestions??

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Old 10-05-2002, 10:37 PM
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You have some sort of parasitic draw. Either something is left on draining the battery, or the battery itself has an internal short. Which is quite possible since the battery went dry, usually when they go dry the lead plates crack and short together. Used to run into that all the time when I was a Saab tech, the batteries used water all the time. They need to be checked at every oil change, more in the summer.

Hope that helps a bit!!
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Old 10-13-2002, 02:20 PM
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Thumbs down bad news ....

you describe the symptoms of a battery that has at least one failed cell.

Check the specific gravity of all the cells and you will find at least one cell with a markedly lower value. This test will just confirm the bad news ...

the dry battery got ruined ....

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Old 10-13-2002, 09:31 PM
Mike Murrell's Avatar
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Join Date: Feb 2000
Posts: 2,359
I agree with Loius - one or more cells went dry and that's that - it's gone.

I haven't seen a self-maintainable auto battery in years, but that's how it is in the U. S.

12 volt batteries contain 6 cells and the ideal charge in each is 2.1 volts. 6 x 2.1 = 12.6 volts - the ideal reading one would get with a VOM set on the 20 scale and after the auto had been at rest for 6-8 hours.

If you cancel out one cell(2.1 volts), and the other 5 are healthy(2.1 volts each), you're down to 10.5 volts. That won't work. In all likelyhood if one cell is dry the others are probably below optimum.

Time for a new battery.
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
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Old 10-13-2002, 09:42 PM
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Just replaced mine last week.

Sounds like your alternator is working fine when running, bright lights therefore the assumption would be (I am crappy at electronics) alternator is trying to charge battery and battery is unhappy and not taking / storing charge.

Therefore as others have said.

New battery time.

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Old 10-16-2002, 07:21 PM
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Thanks All...

Just returned from an oversees trip since I posted that message and will get the new battery tomorrow. Thanks for all the good information.
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