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Battery drain when parked. Is it too much?

Discussion in 'A3/S3/Sportback (8P Chassis)' started by JVG, Oct 13, 2013.

  1. JVG
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    JVG 2007 A3 8P

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    [Oct 13, 2013]
    Hi all,

    I got my 2007 A3 2.0 TDI on August 2012. Due to several reasons, it has spent most time since them unused. Well, that lead to a couple battery discharges which I thought were due to not using the car... Then, when I have tried to use the car, I have found that perhaps the problem was not just the car sitting for too much time but that there is an excessive battery drain when car is parked.

    Thinking that the old battery was bad, I got a new one this week. I measured 12.60V on it as it came from the store, so I put it on my battery charger overnight. It is a good one, a CTEK MXS 5.0. Next day, battery was charged and I put it on the A3. Battery voltage, once connected, was about 12.8V. So far, so good.

    But then, next day, I found that battery voltage was down to 12.63V. Yes, still seemed like it hold a decent charge, but I wondered if the car was draining too much when parked. Of course, all interior lights were off and there were no accessories connected. So I put the Fluke 77 III meter in DCA mode and measured the drain. It started after the battery connection at about 1.5A. Then it fastly dropped to 1.0A and then to 0.5A or so. And, finally, in a minute or so, it went to 0.17A (170mA). And it sits there, at least for 15 minutes or so (I have left the meter measuring and will check later, just in case it goes to some kind of sleep mode)

    But, supossing it keeps draining 170mA, I think it is by far too much, as that would mean a 4.08A/h discharge in a day and 28.56A/h in a week. As battery is a 70A/h unit, that would mean a dead battery in about 2 weeks!

    So, please, does someone know which should be the current drain on a car like mine?. If mine is too high, which would be the primary suspects?. Would you use the trick of removing fuses to find it?

    Thanks for your help and best regards,

    JOSE
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  3. leegsi
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    leegsi Active Member

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    [Oct 13, 2013]
    Being Canbus some systems will be live for a short time and as they go into standby the current will drop.

    Less than 50mA is normal I think.

    Only wat to find what is drawing current would be to start pulling fuses and see when the current drops.
    Last edited: Oct 13, 2013
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  4. JVG
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    JVG 2007 A3 8P

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    [Oct 13, 2013]
    Hello!

    Well, I read your first message with a 200mA value and got surprised. Now, the 50mA sounds more reasonable ;-)

    I have checked and, after about 20 minutes, current was down to 150mA and kept that way. So, yes, something is draining the battery.

    I have removed fuses until I have found that removing FUSE 2 from the engine fuse box (a 5A unit which, according to the manual, is for the steering wheel electronics), consumption has dropped to almost null.

    Then I have thought that perhaps it has to do with having the key permanently on the ignition switch, as I park the car inside the garage in my house and leave it opened. Could it be that?. I plan to check with the car closed, but I am curious to know in advance :)

    Regards,

    JOSE
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  5. fangio
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    fangio Well-Known Member

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    [Oct 13, 2013]
    Remove the key and everything that should, shuts down. If you want to leave the key in the ignition, put it back in without turning it.
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  6. JVG
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    JVG 2007 A3 8P

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    [Oct 13, 2013]
    Yes, I have just checked it, with the key removed... and in just a couple minutes, it is down to 30mA

    Well, sometimens, to learn things, you should do it the hard way!

    BTW, I work all days with electronics (you can check my WEB at EB5AGV Amateur Radio and Test Equipment and also my small company at http://agvradio.com), but mostly on radio and test equipment.

    Does someone need a brand-new 70Ah battery for his/her A3 :whistle2:?

    I will recharge the battery, leave the car closed <G>, and check again in some days. I guess I will find the battery keeps its charge properly :yes:!

    Thanks and best regards,

    JOSE
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  7. leegsi
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    leegsi Active Member

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    [Oct 13, 2013]
    It was a few years ago I did it at college and had to go back through my notes as 200mA sounded high lol
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