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SL battery warning light

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by sl5, Dec 16, 2012.

  1. sl5

    sl5 Senior Member

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    Your Mercedes:
    SL500 R230 11/2002
    hi

    i have been trying to fix this battery warning light ever since., '...visit workshop'.

    i have replaced the alternator regulator.. it was fixed then after 2 hours, it started again..

    now, everytime i turn on the engine, it says 'consumer electronics offline'
    and have to restart the car in order for my steering, seat to set to my set configurations...
    maybe rear consumer electronics battery is dead.

    and would this be why i am getting this warning light? can i recharge this or do i have to buy another battery..
     
  2. drmw

    drmw Moderator

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    Your Mercedes:
    M6 Cab - prior to that, SL63 AMG, A-M V8 Vantage, SL55, SL500 and many more
    If the alternator has been replaced, then this is indeed the battery failing to hold enough charge.

    Cold weather and batteries on their way out do not go well together!
     
  3. OP
    sl5

    sl5 Senior Member

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    hi

    no, the regulator was changed only

    which battery needs changing, front or back?
     
  4. OP
    sl5

    sl5 Senior Member

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    I mean regulator was only changed not alternator
     
  5. television

    television Always remembered RIP

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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    Hello, you do need a voltmeter to check and see what is going on. I take it its a 230 SL
    You need to check across the rear battery to see that you have around 13.8 volts with the engine running. If the voltage is staying at around 12volts, then the alternator is not charging or the battery control ECU is not working, this is the one behind the rear battery in the boot, the front battery is for the starter only
     
  6. OP
    sl5

    sl5 Senior Member

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    hi

    ok, thanks. i just took the readings..

    front battery,
    normal: 13.3 v
    engine on: 14.6v

    rear battery
    normal: 12.1v
    engine running: 14.0v

    does this normal?
     
  7. television

    television Always remembered RIP

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    Yes that is perfect.

    You must remember that it will take up to 20 hours to get the rear AGM battery back to its full charge, this is on a 4 amp charger
     
  8. OP
    sl5

    sl5 Senior Member

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    so youre saying i should just charge the rear battery first with a external charger instead of buying one?

    if i do remove the battery, would it wipe out any system configs, memory,etc after a certain time?
     
    Last edited: Dec 16, 2012
  9. television

    television Always remembered RIP

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    Your Mercedes:
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    Most of these AGM batteries are good for 10 years

    If you disconnect it, you will have to reset the windows and possibly the roll bar, the ESP lamp will go out on its own when driven.

    My SL was never used that much and every 2 weeks I gave the rear battery a good charge or the "consumers off line" message would be up for some time.

    The SL draws high current for some time each time you turn off, this is while the car is going to sleep.

    Charging the rear battery works wonders, and the charger best left on till the charge drops to 2 amps or just under.

    My 2002 AGM battery from my SL is in daily use still in my CL do charge it first, it can take a 500 mile trip to get the battery to the same good level
     
  10. OP
    sl5

    sl5 Senior Member

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    thanks... i am now charging the battery in doors.. so its around 20hours? untill fully charged?
     
  11. television

    television Always remembered RIP

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    When you refit it,,, just turn the key to ignition on, close each side window on the the slow lift and hold the switch in that mode for 5 seconds.

    There should not be anything else, the ESP will go out as you drive
     
  12. OP
    sl5

    sl5 Senior Member

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    i started charging my battery, after 1 hr, it says 'fully charged'..

    whats going on? is it dead?
     
  13. television

    television Always remembered RIP

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    Where does it say fully charged, what was the current going in
     
  14. OP
    sl5

    sl5 Senior Member

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    4amp

    it said it on my external battery charge.. greeen led, fully charged.
     
  15. television

    television Always remembered RIP

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    Its hard to know what to say as AGM batteries have different charging characteristics over a lead acid, I do know that it is easy to get the AGM batteries up to 12v, its getting that last Ā½volt that can take the time.

    Try it you never know
     
  16. SL55 Mark

    SL55 Mark Senior Member

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    I don't think you have the right sort of charger. It needs to be AGM specific, a trickle charger/conditioner. Mine takes 20 plus hours as Malcolm says. It has a complex charging cycle, which is designed not only to charge the battery, but to gradually restore it to full health.
     

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