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[SOLVED] Battery draining?

Discussion in 'Electronics' started by greekCL, Dec 3, 2011.

  1. greekCL

    greekCL Hardcore MB Enthusiast

    Messages:
    403
    Joined:
    Jun 15, 2008
    Location:
    Kent
    Car:
    Mercedes CLS500 (2005)
    Hello guys,

    Been having a problem recently with my CL500 ... seems to drain the battery below 9.0V in 3 days ... of sitting.

    I have charged the battery on my charger yesterday ... and today the battery was showing 12.8V ... I suppose better than nothing
    I have recruited a friend with V/Amperometer and put it on the battery to check drainage ...

    Here are the figures, let me know if they seem normal or do I need to dig in more.

    Battery is a 100AH

    With the aftermarket stereo front but everything switched off
    About 200mA (0.2A) drainage

    Without the stero front on and everything closed ..boot, bonner, doors .. everything
    About 75mA (0.075A) drainage

    I am going to park the car from now on without the stereo face on and see if that 0.075A is enough to drain the battery so low.

    The car does not do big trips usually ... maybe a 14miles journey 3-4 times a week.

    Cheers
    Vasilis
     
  2. BTB 500

    BTB 500 Hardcore MB Enthusiast

    Messages:
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    Joined:
    Aug 7, 2005
    Location:
    Berkshire
    Car:
    R129 SL500, 639 Vito 120 Dualiner Long, S203 C230 Avantgarde SE Sport
    Sounds like your battery has had it. 9.0V is effectively dead (fully discharged is 11.9V).

    To lose 100AH in 3 days you'd need a constant current of approx. 1.4 amps, which you are nowhere near.
     
  3. OP
    OP
    greekCL

    greekCL Hardcore MB Enthusiast

    Messages:
    403
    Joined:
    Jun 15, 2008
    Location:
    Kent
    Car:
    Mercedes CLS500 (2005)
    Whoopps... the company I got the battery from is saying that there is something draining the battery. Hence they will not admit that there is a fault with the battery.

    I have removed the headunit face tonight ... I just remembered earlier actually ... that when I was living in London I used to always remove the headunit face.
    However since I moved out of London ... due to parking the car off the road stopped taking it off... this is more less when the batteries started getting weaker.

    I will monitor and provide an update ;) Thanks Bill.
     
  4. steve333

    steve333 Hardcore MB Enthusiast

    Messages:
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    Oct 22, 2009
    Location:
    Dorset
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    Ml300 grand edition iridium silver,2014 slk250cdi tenorite grey
    Ask them to give you another battery for a few days on loan to see if that discharges then you will know something is draining it otherwise if all is ok then the original battery supplied is at fault?
     
  5. cl55 amg

    cl55 amg Hardcore MB Enthusiast

    Messages:
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    May 28, 2009
    Location:
    Manchester
    Car:
    CL55 AMG
    Can I ask what battery you use? I had the same issue so gave it to a auto electrician where he monitored it for three days and could find no drain. he recommended replacing the battery with a Bosch.
     
  6. jefrs

    jefrs Hardcore MB Enthusiast

    Messages:
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    Joined:
    May 30, 2010
    Location:
    Berkshire
    Car:
    S210 E320 Avantgarde '98 full load
    Holding 12.8V is perfect, but discharging to 9.0V is bad.

    0.2A should not / cannot drain a battery down to 9.0V in three days

    100Ah is 1 A for 100 hours. 72h x 0.2A = 14.4Ah

    A car battery is "discharged" at 12.2V so 9.0V is very dead.

    Even though you can charge it to the correct 12.8V, is it holding that that charge for long? You need to determine whether it is discharging itself i.e. by measuring off the car for some period after charging, e.g. at one day, two days. three days. A faulty battery can discharge itself.
     
  7. OP
    OP
    greekCL

    greekCL Hardcore MB Enthusiast

    Messages:
    403
    Joined:
    Jun 15, 2008
    Location:
    Kent
    Car:
    Mercedes CLS500 (2005)
    OK it was the headunit ... once I take off the face.
    The car battery can last a whole week between car starts.
    I think the battery being a cheap one does not help... but hey it does the job for now.
     

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