Car doesn't start because of weak battery. But starts after 4 tries. Why?

Discussion in 'The Garage' started by fuzzybabybunny, Feb 16, 2013.

  1. imagoon

    imagoon Diamond Member

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    You're lucky you didn't fry both the charger and desulfinator. They are not designed to be used together.
     
  2. fuzzybabybunny

    fuzzybabybunny Moderator<br>Digital & Video Cameras
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    Many things are not designed for this and that. But they can still be used for that purpose, regardless. Why, electronically, would it fry the charger and charger/desulfinator if used together?
     
  3. LTC8K6

    LTC8K6 Lifer

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    The desulfinator applies rapid high current pulses to the battery when it's connected by itself, I don't know what the interaction would be with a regular charger in parallel.
     
  4. phucheneh

    phucheneh Diamond Member

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    Jesus freakin' christ THIS^.

    FBB, you're still acting as if the battery operates on invisible voodoo magic.

    You may have a bad battery or alternator cable for all we know.

    You said the battery tested bad with a conductance tester. I do not recall you sharing the actual results.

    You said the battery measured 11.86v. That is almost completely discharged.

    Neither of these things are terribly conclusive, unless the tester gave a very obviously bad result (e.g. measured 100cca). We also don't know how much your battery actually charged, and you did not bother checking voltage after (assumably) charging.

    Point being, 100 replies are you are still at square one because you are ignoring simple questions/advice, apparently in favor of doing everything you can do cling to your possibly-bad-but-we-still-have-no-idea battery.

    Please get a voltmeter. You can get one that will measure voltage accurately enough for the cost of a Happy Meal.

    Then, put the battery in your car and tighten the connections. Flip the headlights on for a few second to get rid of any surface charge, if it has recently come off a charger (I would just do it anyway to make sure the voltage stabilizes).

    Turn everything off, including the ignition switch (pull the key out), close the door, and measure the voltage with the probes directly on the battery posts (the round bit coming out of the battery, not what clamps onto them.

    Record this voltage. If it is not ~12.4v volts or more, it's not even close to fully charged. But if it's at least about 12.1v, we will continue testing.

    Get a helper. Have them try to start the car while you keep your probes on the battery posts. It doesn't matter if it cranks or how fast- just tell them to keep turning the key forward while you observe the voltage.

    Most likely, you will see it drop. A lot. <10v.

    What have we determined from that? That the battery is likely shit...but we want to do one more thing.

    Repeat the cranking (load) test, but with one probe on the negative post and one on a good ground (stab a shiny part of the engine). If you read more than a quarter of a volt, you have a ground issue.

    Repeat that test once more, but go from the positive post to the big terminal on the starter. Again, any significant voltage reading is bad.

    A Honda Fit (literally pretty much any of them...that's a fairly new model) should not have cabling issues. If it's never had a starter and no one's fucked with the battery terminals, the cables are likely fine. However, you can also simply test between the battery post and the terminal. Even though the terminal may LOOK tight and corosion-free, it's not impossible to be losing voltage between the post and the terminal. Also, when cables go 'bad', it's usually just that the end of the cable has oxidized; I've probed into cables a mere inch or so down the line, and found almost all the battery voltage being dropped across that area. You don't HAVE to do these vdrop tests, and I doubt they will expose a problem, but it's a good idea.

    Again, a low voltage reading between the battery posts during cranking will strongly indicate a bad battery. That is the single most important thing you can you do. But I'm trying to get across how invaluable a voltmeter is. You can troubleshoot every single aspect of a starting/charging problem with very few exceptions.
     
    #104 phucheneh, Feb 21, 2013
    Last edited: Feb 21, 2013
  5. fuzzybabybunny

    fuzzybabybunny Moderator<br>Digital & Video Cameras
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    Tomorrow I'll go and borrow one from K-mart or Radio Shack. By borrow I mean buy it, use it to do this test, and return it the next day.

    Seriously, I am NOT buying another stupid voltmeter / multimeter. I've bought 4-5 in my life. I've used them 4-5 times. Not days. Not projects. Times. As in, I put the leads on something for a few seconds. I've needed to do this 4-5 times. In my entire life. I have a "need" for one maybe about once every 3 years and afterwards it goes into storage and is never seen from again. And the results always seem to be what I already know. Whatever it is is bad and just needs to get replaced.

    I went to another auto store. I charged up the battery this morning (I know it's charged because the chargers automatically go into Maintenance mode when it is fully charged, and it was in Maintenance mode this morning) and it had a hard time cranking in the cold morning. At the end of the day around 6PM I took it to the auto store and it still read "bad battery" even though it read 12.29V. It also said that it was at 58% capacity. After just a day of basically sitting around from a "fully charged" state.
     
    #105 fuzzybabybunny, Feb 22, 2013
    Last edited: Feb 22, 2013
  6. phucheneh

    phucheneh Diamond Member

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    Jesus. It's. Five. Dollars.

    And you're blaming those that are trying to help you for your inability to keep track of shit. It sounds like you need a meter, anyhow, to keep track of when you need to throw your battery on the charger while at home. You can get one that plugs into your cigarette lighter for like five bucks or less on eBay. I've been meaning to get one...I was gonna hardwire it in (I only have one 'constant on' outlet) with a momentary switch and mount it in my armrest or something. When I want to check approximate SOC, I just need to push the button and read the display.

    The testers at Autozone/Advance/ect are conductance testers. It measures the ability of the plates to conduct current, IIRC (might be an oversimplification). Voltage/SOC is not a big factor. Technically, it should not be a factor at all, but a good charging is sometimes the difference between borderline failure and borderline passing.

    Once again: share the result of the test with us. ~12.3v should be accurate enough to get a solid test. It should give you a CCA number; that's why you input the rated CCA before testing. It's just a comparison between the rating and what is calculates based on its measurement.

    If your batt was at that voltage, it was not fully charged. The cells may be too degraded to make a true 12.6v (2.1v each), I guess. But more than likely, your 'automatic' charger just sucks. Most do.

    58% charge is in the ballpark for that voltage. Your battery did not discharge 42% from sitting. It's, unsurprisingly, probably just bad.

    If you can't afford a voltmeter, you can't afford a battery. Or a cable. Or even a pair of basic lead battery terminals. So I guess we're done here.
     
  7. nerp

    nerp Diamond Member

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    The problem is you're trying to use the wrong battery in a car for the wrong reasons. You need to use a regular car battery in your car and find a way to keep your laptop charged that doesn't involve a screwed up system that doesn't work.
     
  8. HeXen

    HeXen Diamond Member

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    LMAO, wow, page 3 over a simple car battery with simple solutions.