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Battery problem

  • 01-12-2013 10:13pm
    #1
    John Kelly of
    Registered Users Posts: 382 ✭✭


    Hi I have an Isuzu trooper 2000.
    If I leave it without driving for the weekend it won't start on Monday morning.
    However when I put a meter on the 2 batteries they both show 12.6v which indicates the batteries are ok.
    If I attach jump leads from a doner car it will start which doesn't make sense to me.
    Can anyone explain this?


Comments

  • #2
    aujopimur
    Registered Users Posts: 3,953 ✭✭✭aujopimur


    A voltmeter won't show the condition of the battery, your local motor factor will load test it for you.


  • #3
    visual
    Closed Accounts Posts: 3,268 ✭✭✭visual


    Check the battery terminals
    Its hard to spot corrosion on mating surface between battery pole and terminal.
    Use fine sandpaper, wire brush or battery brush claen surfaces well and ensure terminals are on tight. If probem persist get battery tested.


  • #4
    keithsfleet
    Registered Users Posts: 1,072 ✭✭✭keithsfleet


    The battery is producing that voltage under no load. Turn the key and try starting it while testing it will show what voltage it's putting out under load.

    Sounds like the battery needs replacement.


  • #5
    dooroy
    Registered Users Posts: 576 ✭✭✭dooroy


    It would be a good idea , as advised , to remove and clean ( to a shiny look ) all battery connections , earth straps etc.
    Connections can be tight but corrosion can build up between terminal connection and battery pole . When pole and terminal are clean and shiny then smear pole with petroleum jelly ( Vaseline ) and replace . Do not use ordinary grease . And make sure terminals are clamping onto poles properly.


  • #6
    guil
    Registered Users Posts: 10,475 ✭✭✭✭guil


    What volts should the battery be putting out while trying to start it?


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  • #7
    cnocbui
    Registered Users Posts: 19,651 ✭✭✭✭cnocbui


    If the battery is more than 3 years old, replace it.


  • #8
    John Kelly of
    Registered Users Posts: 382 ✭✭John Kelly of


    thanks guys
    thanks for the advice.
    just wondering which of the batteries to replace, or should I replace both?
    I dont know how old they are as I bring it in to be serviced every year and they have taken care of the them in the past.
    I disconnected both batteries and put the meter on them
    1 battery is steady at 12.6 v
    the 2nd battery fluctuates for about 5 seconds and then settles on 12.6v
    does this mean I only need to replace the 2nd one?


  • #9
    biko
    Registered Users Posts: 81,223 ✭✭✭✭biko


    Test batts when engine is running.
    You may have to replace both.


  • #10
    aujopimur
    Registered Users Posts: 3,953 ✭✭✭aujopimur


    Read post 2


  • #11
    cnocbui
    Registered Users Posts: 19,651 ✭✭✭✭cnocbui


    biko wrote: »
    Test batts when engine is running.
    You may have to replace both.

    No, you would then be testing the alternator output.


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  • #12
    jomoloney
    Registered Users Posts: 859 ✭✭✭jomoloney


    replace the 2

    we usually get 6 to 7 years from these

    as for the connections tnere is an area often forgotten

    where the clamp joins the leads , if thses arnt soldered you can get corrosion inside

    don;t think the connection are at fault other wise you would have problems each morning and not just after weekends


    you need to get the batteries tested under load & not with the engine running


  • #13
    Avns1s
    Registered Users Posts: 3,422 ✭✭✭Avns1s


    If you can open the battery and observe for "gassing" in one or more cells. If there are bubbles, the cell is done - as in, the battery is finished.

    CAUTION: Looking into the cells of a battery like this should be done through a piece of clear glass left over the battery in case of splashing from the cells onto the eyes / skin!.


  • #14
    Renegade Mechanic
    Registered Users Posts: 7,934 ✭✭✭Renegade Mechanic


    A few rules for battery/starting/charging that you wont go too far wrong by.

    Charging voltage should be 14v running with no load, be sure this is the case or the battery isn't being charged properly. Anything under 13.6v is not good enough.

    A standing battery should have around 12v as you know but less than 11 and it will more than likely need a charge/replacement before the car will start.

    Now onto the test you need to do. Place a voltmeter on the battery and make sure you can see it while cranking the engine. If it starts, great. But if it doesnt, keep the key fully engaged for 6 seconds anyway. If the voltage drops below 9.6v then the battery is no longer useful. Usually to test a battery without proper equipment Ill disconnect something to prevent the car from firing. Wether the engine cranks (however slowly) or the starter just "clicks" doesnt matter, only the result. For 6 seconds the voltage musnt drop below that number. If it does not, something else is to blame. If it does then the battery is to blame. Ive had many 12v + batteries drop to under 5v under simple cranking, not to mention a proper load test!


  • #15
    John Kelly of
    Registered Users Posts: 382 ✭✭John Kelly of


    great advice thanks


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