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Auto battery question

Discussion in 'Electronic Basics' started by Sam the Bam, Sep 8, 2005.

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  1. Sam the Bam

    Sam the Bam Guest

    A few days ago, my car wouldn't start. The dashboard
    electronics were all working, so I figured it's a
    dying battery. I didn't have time to fix it, so the
    car sat in the street. (I have another vehicle)

    This morning, the battery was totally dead. No electric
    power. I asked a neighbor for a jump start, we hooked
    it up, and again the starter wouldn't respond. However,
    the electronics were operating, so it's not the regulator or anything.

    I thought, oh oh, problem! Starting motor burned out,
    or frozen engine. Then I thought: what else could it
    be? Maybe the battery is shorting out the circuitry,
    is that possible? That means when we tried the jump
    start, the battery drew all the current, leaving
    nothing for the starter.

    So I unhooked the battery, and asked another neighbor
    for a jump, directly to the cables. But he refused!
    He said, without the battery, his alternator could
    blow out. I.e. my battery 'protects' his charger.

    Could he be right? It doesn't make sense to me.

    Any suggestions appreciated -

    Sam
     
  2. Uncle Al

    Uncle Al Guest

    You are supposed to check the electrolyte level in your battery -
    monthly for standard issue, every six months for "no water"
    batteries. Use only distilled water for makeup. Carefully wipe the
    electrolyte caps, battery top, and electrodes. Smear silicone grease
    on the electrodes to prevent corrosion (especially the hot terminal).

    The system is designed to have the battery attached as buffer. Start
    the good car. Hook the hot sides with the jumpers then hook the
    grounds. Race the good car's engine as you start the dead car.
    Unless the dead battery is shorted the car will continue to run.
    Drive down to Sears, have your diodes checked, and buy the biggest
    DieHard that will fit. A DieHard will give you up to 8 years of
    service if you treat it well. (What does that say about the projected
    longetivity of hybrid autos?)

    If you are in Europe you might want to check before hookup that both
    cars use the sane sign convention for ground. English ignition
    electronics are diagnostic of how far the Industrial Revoluton
    penetrated inot the mob.
     
  3. mike

    mike Guest

    Would be helpful to know the make/model/year of your
    vehicle. Advice for a 53 Chevy might be diffrerent than
    for a 2004 Peterbuilt.

    If the starter is getting juice and the motor is locked,
    you'll know it.
    Modern cars have a bunch of interlocks on the gear shift,
    clutch etc. to prevent you starting the car unsafely.

    I thought I had a dead starter once. Turned out that
    I wasn't depressing the clutch far enough to hit the
    starter enable switch.

    If your headlights didn't dim when you hit the starter button,
    your battery being dead wasn't the immediate cause of your original problem.
    mike

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  4. Tom Biasi

    Tom Biasi Guest

    Hi Sam,
    Anytime you jump start another vehicle with yours you risk damage to your
    alternator.
    You don't know what kind of problems caused the dead battery condition.
    Most of the time the dead car starts and you are on your way, but it is
    possible to damage your regulator, or diodes if the conditions are right.
    As for hooking them to the cables, the only additional risk is shorting to
    chassis and risking damage to the system.
    You would accomplish nothing by this anyway, your car wouldn't run long
    after he removed his battery.
    See if your dead battery will take a charge, if not, get a new one and drive
    the car to have the charging system checked.
    Check also for current draw when the car is off.
    As an aside, it is quite common for a battery to operate the electronics but
    not start the car. The electronics take relatively low current that the
    battery usually can still supply. The connections should be checked first,
    this is the most common cause.
    Regards,
    Tom
     
  5. Ace

    Ace Guest

    I had similar problem and found one of the battery cables (don't recall
    which) was corroded so badly a wire was interrupted. The tail end of the
    cable had a couple other wires going going different places??????????

    Oh, the cable was corroded inside the protective sheath, not between
    terminal and the round connector. The battery had been using a lot of
    water, but I ignored it. Guess the fumes did their number.
     
  6. nailer

    nailer Guest

    you start the secondcar, you connect the leads to the battery in the
    first car, you connect the leads to the battery in the second car
    (with a positive terminal disconnected). you start the engine in the
    second car.
     
  7. nailer

    nailer Guest

    R u sure, the starter motor is not disconnected? Otherwise follow UA
    advice.
    I would not expect all cells to be shorted, so you should get some
    (lower) voltage, insufficient to start.
    How often is you car being used? How many miles per week?

    On Thu, 8 Sep 2005 18:26:56 -0400, "Tom Biasi"

    *
    **>A few days ago, my car wouldn't start. The dashboard
    *> electronics were all working, so I figured it's a
    *> dying battery. I didn't have time to fix it, so the
    *> car sat in the street. (I have another vehicle)
    *>
    *> This morning, the battery was totally dead. No electric
    *> power. I asked a neighbor for a jump start, we hooked
    *> it up, and again the starter wouldn't respond. However,
    *> the electronics were operating, so it's not the regulator or anything.
    *>
    *> I thought, oh oh, problem! Starting motor burned out,
    *> or frozen engine. Then I thought: what else could it
    *> be? Maybe the battery is shorting out the circuitry,
    *> is that possible? That means when we tried the jump
    *> start, the battery drew all the current, leaving
    *> nothing for the starter.
    *>
    *> So I unhooked the battery, and asked another neighbor
    *> for a jump, directly to the cables. But he refused!
    *> He said, without the battery, his alternator could
    *> blow out. I.e. my battery 'protects' his charger.
    *>
    *> Could he be right? It doesn't make sense to me.
    *>
    *> Any suggestions appreciated -
    *>
    *> Sam
    *>
    *
    *Hi Sam,
    *Anytime you jump start another vehicle with yours you risk damage to your
    *alternator.
    *You don't know what kind of problems caused the dead battery condition.
    *Most of the time the dead car starts and you are on your way, but it is
    *possible to damage your regulator, or diodes if the conditions are right.
    *As for hooking them to the cables, the only additional risk is shorting to
    *chassis and risking damage to the system.
    *You would accomplish nothing by this anyway, your car wouldn't run long
    *after he removed his battery.
    *See if your dead battery will take a charge, if not, get a new one and drive
    *the car to have the charging system checked.
    *Check also for current draw when the car is off.
    *As an aside, it is quite common for a battery to operate the electronics but
    *not start the car. The electronics take relatively low current that the
    *battery usually can still supply. The connections should be checked first,
    *this is the most common cause.
    *Regards,
    *Tom
    *
     
  8. roma

    roma Guest

    Back in the olden days a hammer was a very usefultool to have around to
    hit the stucked open starter solenoid , aside from that everything else
    looked normal .
    Old timer , roma
     
  9. Mike Berger

    Mike Berger Guest

    Those class-action lawsuits about defective diehard batteries
    and fradulent repair at sears doesn't discourage you?

    \
     
  10. Uncle Al

    Uncle Al Guest

    My 1989 VW Golf recently started on its third Diehard. It works for
    me. Sears is no problem if you stand there watching the wetback work,
    making the occasional helpful comment when he puts a peeled banana
    into the crankcase.

    "Hola, pendejo..."
     
  11. Some 10-year-old cases, settled and fixed, still bother you? You must really
    lose sleep over the fall of the Roman Empire.
     
  12. Not "fall", "collapse" (gene-pool
    failure, or boredom, I forget which :)


    Atty (Mebee dey gived wemen right to vote?)
     
  13. Don't forget, the battery acts like a shock absorber for the car's
    electronics. Running a newer car on alternator power only has the
    potential to ruin vehicle electrical systems because of the spikey
    voltage the alternator produces. The battery absorbs and smoothes the
    spikes.

    I can't imagine hurting your neighbor's car by jumping your vehicle
    with your battery disconnected. But it is his car, and you play by
    his rules.

    Having a partially dead battery go flatline in a short time makes me
    think you have a short somewhere.

    After checking to make sure you didn't leave your headlights or dome
    light on, you might have to look a little farther.

    Granted it, could be a bad battery, but I've never seen one go
    partially dead, then completely dead. Usually they won't hold a good
    charge, or they are completely dead (open internally)

    I had a diode go bad in an alternator once.
    I found it accidentally. While I was attempting to check the
    alternator's output (engine cold) I noticed the alternator was warm to
    the touch. The diode was getting hot, and draining the battery.

    Don't jump to conclusions too quickly about a bad battery.
     
  14. Sam the Bam

    Sam the Bam Guest

    That's what I figured. I don't see how my battery being
    disconnected is a hazard.
    Why not? As I understand it, the alternator runs everything
    after start up. Is there an interlock, which shuts down the
    system if it detects an open circuit condition?
    Any service garage can check for this?
    How to do this? There are no gauges on the dashboard.

    Sam
     
  15. Sam the Bam

    Sam the Bam Guest

    I see, that's the 'buffer' explanation.
    So as long as his battery is OK, it shouldn't matter
    if mine is disconnected.


    I'll try this, but I have to get the car started first...
    It's hard to troubleshoot, if it isn't the battery.
    I'm leery about going to a mechanic, and saying,
    "I don't know what's wrong, check it out" - that's
    how you get shaved.

    Sam
     
  16. BobG

    BobG Guest

    Don't ever disconnect that battery once the engine is running, because
    the alternator, which was happily charging the battery when it was
    connected, will suddenly see the charging current drop, and shoot the
    charging voltage up to 60V. This is called a 'load dump' and makes for
    lots of fried 12V electronics.
     
  17. Sam the Bam

    Sam the Bam Guest

    That may be true, but it's crappy design, and borderline
    incredible. It's easy to design a shunt which detects
    an open circuit condition.

    Sam
     
  18. Tom Biasi

    Tom Biasi Guest

    The alternator does not run everything, the battery runs everything. The
    alternator keeps the battery charged.

    Any service station that does electrical work.
    The station can check for this.
     
  19. Howver, if your car does start, and you then disconnect the jumper
    cables, your alternator voltage will rise uncontrollably, since the
    battery (now disconnected) will normally prevent the system voltage
    from rising above 14V or so.

    With no battery, the voltage will rise enough to destroy the diodes in
    your alternator, and also most of the electronics in your car.
     
  20. kell

    kell Guest

    get a new one and drive
    You can check the car for current draw easily if you have a multimeter.
    Set the multimeter to measure current; put it on the highest setting.
    Disconnect one of the battery cables and use the multimeter's leads to
    complete the circuit you have just broken. The meter will tell you
    exactly how much current is drawing.
    You can check for a bad diode in the alternator. With the car off,
    disconnect the heavy wire from the alternator and do the same
    multimeter test.
     
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