Dead battery? Or is there any hope? - Page 2
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This is a discussion on Dead battery? Or is there any hope? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Alright well I purchased a battery charger (a DieHard automatic battery charger) and I used it on my Optima. It ...

  1. #16
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    Alright well I purchased a battery charger (a DieHard automatic battery charger) and I used it on my Optima. It said that it charged it to 12 volts, so I figured it was good enough to start my WRX. Well it did provide enough juice to use my accessories, but it would not start the motor on the vehicle. I hooked up jumper cables off of my Xterra again, and it started, and it ran at about 1500RPMS for a minute, but then it got down to about 1000RPM and started to idle very rough.

    So the battery is at 12 volts, shouldn't the alternator be able to charge it and I shouldnt have any problems at this point?

    Any further suggestions?

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  3. #17
    Moderator Donkey's Avatar
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    Quote Originally Posted by pfcrangel View Post
    So the battery is at 12 volts, shouldn't the alternator be able to charge it and I shouldnt have any problems at this point?

    Any further suggestions?
    Did you test the battery with a DDM once the car was running? This would have been able to tell you if the alternator was good or not. Buy a cheap DDM (Digital Multi Meter) and learn to use it. It could save you money. No offense but this could go back and forth forever. It sounds like you know very little about auto mechanics and basic car operation. It might be best to get the car professionally looked at. Could be a bad battery cable,bad ground. Also what AP map(s) did you install and are they Cobb's maps?
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  4. #18
    OMG WTF MainFrame's Avatar
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    Did you put the charger on the "trickle" setting and allow it to charge for at least 24 hours?


    After sitting on the trickle charger the battery should have no problem starting the car by itself(if it's still good). If the battery was on the charger for the proper amount of time, on the correct settings, and it was still unable to start the car then the battery is no good. The alternator should charge the battery over time, but if your alternator is bad you should be able to start the car after charging the battery(or jumping it off), but after you drive somewhere your battery might be dead again and need another charge(or jump) to get it started.

    And like Donkey said, you should go ahead and get a DMM. They're only like $7 for a decent one. I only use mine maybe once a month, but at those times I don't know what I would do without one.
    Last edited by MainFrame; 07-12-2010 at 01:41 PM.

  5. #19
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    pfcrnagel, at 12 volts, most batteries are only at about a 50% state of charge. Fully-charged RedTops will read approximately 12.6-12.8 volts and fully-charged YellowTops will read approximately 13.0-13.2 volts. As Donkey suggested, if you test your battery voltage while the engine is running, it will indicate the output of your alternator, which should be approximately 13.7-14.7 volts.

    As I mentioned before, most alternators are designed to maintain batteries, not recharge deeply-discharged batteries. Relying on your alternator to recharge a deeply-discharged battery can lead to a cycle of dead batteries and jump-starts, until either your battery or alternator fails. Please keep us posted on your progress.

    Jim McIlvaine
    eCare Manager, OPTIMA Batteries, Inc.
    www.facebook.com/optimabatteries

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