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Thread: Car battery question...

  1. #1
    Join Date
    Sep 2007
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    Car battery question...

    Wife has a 4.5 year old Mazda CX9 on the first battery.
    Wednesday night she left the dome light on for 20 hours. Next day it wouldn't start. Dome light was still bright though.

    I put a charger on it. It showed 12.2v. I charged it for 3 hours at 15a, and 1 hour tapering down to 2a, and it showed 14.2v. As far as I can tell, it is a 55ah battery, so the charging seems right on.

    The last two days it has been fine.

    We got the car to haul kids back and forth to college, but that is over and we want to get something smaller; probably after we see the 2019s. (unless cars get a 25% duty and the prices skyrocket, in which case it is just fine).

    So my question... should I be getting a new battery? I don't want to waste $100, but if I need one, I might as well get it while it is still functioning.

  2. #2
    Quote Originally Posted by Wade Lippman View Post
    Wife has a 4.5 year old Mazda CX9 on the first battery.
    Wednesday night she left the dome light on for 20 hours. Next day it wouldn't start. Dome light was still bright though.

    I put a charger on it. It showed 12.2v. I charged it for 3 hours at 15a, and 1 hour tapering down to 2a, and it showed 14.2v. As far as I can tell, it is a 55ah battery, so the charging seems right on.

    The last two days it has been fine.

    We got the car to haul kids back and forth to college, but that is over and we want to get something smaller; probably after we see the 2019s. (unless cars get a 25% duty and the prices skyrocket, in which case it is just fine).

    So my question... should I be getting a new battery? I don't want to waste $100, but if I need one, I might as well get it while it is still functioning.
    After 4.5 years, your battery is toast, not worth trying to squeeze more life out of it (particularly after a discharge like that.) Buy a new one. Interstate is good. BTW that's a nice car.

  3. #3
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    Take it to an auto parts store and let them test it they can tell you if it has a weak cell

  4. #4
    Quote Originally Posted by Jerome Stanek View Post
    Take it to an auto parts store and let them test it they can tell you if it has a weak cell
    Why would you want to drive around with even the slightest concern that your battery is gonna go out on you? In the "old days" you got plenty of warning that your battery is weak just by being sensitive to how the electrical system was behaving. Nowadays cars have gotten better at hiding battery condition issues from the driver, until one day the car simply won't start. Who needs that, especially on a newer car. The parts jobber can tell you whether a battery could be rehabbed to start a jalopy a few times.

    Down here in the South it's not unusual to have to replace a factory battery in a car after two years only, it's a wear item (heat.) Five years would be a good lifetime anywhere.

  5. #5
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    One repair shop told us our car battery needed replacement a year ago. It doesn't charge to its full amperage or something.

    There is a pair of jumper cables under the back seat.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
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  6. #6
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    I've got a 9 year old Murano, about 3 years ago the dealer said it failed the battery test and should be replaced. Still going strong. I do carry a set of cables but I've always done that. If I lived in a remote location with more extreme weather I might be concerned but in my case a one time dead battery incident would be a minor inconvenience. I'm willing to take the chance.

  7. #7
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    Quote Originally Posted by Doug Garson View Post
    in my case a one time dead battery incident would be a minor inconvenience..
    A decade a go, I had a battery fail by bursting open. In about the same time frame, a friend was getting a jump start from a stranger when his battery bust and acid damaged the finish on both cars. I wonder if such things can happen with modern batteries.

  8. #8
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    Quote Originally Posted by Stephen Tashiro View Post
    A decade a go, I had a battery fail by bursting open. In about the same time frame, a friend was getting a jump start from a stranger when his battery bust and acid damaged the finish on both cars. I wonder if such things can happen with modern batteries.
    Wow, never heard of that happening but then again I don't pretend to be a car expert. Did these failures happen under extreme conditions?

  9. #9
    Quote Originally Posted by Stephen Tashiro View Post
    A decade a go, I had a battery fail by bursting open. In about the same time frame, a friend was getting a jump start from a stranger when his battery bust and acid damaged the finish on both cars. I wonder if such things can happen with modern batteries.
    Batteries haven't changed. Cars have.

    The only batteries that I would trust nowadays are made by Interstate (no affiliation.)

    Of course you know the rule, positive to positive and negative to ground (good battery to bad battery positive plus frame.) If a battery really is dead I wouldn't trust it to be charged by a "samaritan" car w/o risk of damage to same, due to the "sensitivity" of the electronics in a modern alternator, re burning it out etc. Unless we're talking about a heavy-duty samaritan, like a tow truck or something. I would also temporarily disconnect the ground to the dead battery. With modern electronic controls, that's the veddygood voodoo.

  10. #10
    Another thing to be aware of. Used to be that if you were driving along the highway and the battery failed, you could keep going on the alternator. So you didnt know it failed until the next time you stopped/parked. Today, that is no longer true - at least for some cars. The car will shut down right then and there, leaving you stuck next to the highway. I don't know why they build them like that but this happened to my Mom in a late model Ford about 6 years years back. Failed hard and a jump wouldnt do it. We were told by a shop we trusted that the computer expects a certain voltage from the battery and wnen it doesnt see it, shuts down.
    "All that is necessary for the triumph of evil is that good men do nothing."

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  11. #11
    If you have a good ear (I do, fortunately) you can tell when your battery is on its way out just by the slight change in sound-pitch when starting- if it seems like the starter is getting a bit slower or 'labored', it probably is, and you should get the battery checked. Caveats to this, starters run slower as temps go down, oil is thicker.

    When in doubt, just have the battery checked, most auto parts stores do this for free. If the battery passes a load test, odds are high you're good to go for at least a few months...

    I have a 2002 Ford F-250 I bought new, the original battery lasted 11 years, and showed no signs of failure even when it did fail, and it failed in grand fashion by blowing out the side of the case with a "pop". Wasn't a loud pop either, maybe half as loud as a good hand-clap. Somehow a short developed inside, it happens.

    I've always had good luck with batteries, that is until these 1-year cheapies Walmart sells came out. I've bought 2 of them, and both barely made it to 13 months, just long enough to pass the warranty. Almost like they have a timer built in
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  12. #12
    After 4.5 years, I'd change the battery so I wouldn't have to worry about if it might fail on me in an inconvenient place.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  13. #13
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    Quote Originally Posted by Stephen Tashiro View Post
    A decade a go, I had a battery fail by bursting open. In about the same time frame, a friend was getting a jump start from a stranger when his battery bust and acid damaged the finish on both cars. I wonder if such things can happen with modern batteries.
    Was this winter time in a cold climate and the battery that was dead was frozen?
    George

    Making sawdust regularly, occasionally a project is completed.

  14. #14
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    Quote Originally Posted by Doug Garson View Post
    Wow, never heard of that happening but then again I don't pretend to be a car expert. Did these failures happen under extreme conditions?
    The weather wasn't extreme when my battery burst. It wasn't winter or a hot summer day. I don't know the conditions when my friend's battery burst.

  15. #15
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    I am with the majority--spend the $100 and get a new battery.

    Having jumper cables is good, but the battery will give up the ghost when there is no one around or when you need the car in a hurry.

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