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Thread: Battery discharge problem

  1. #1
    Join Date
    Jan 2007
    Posts
    5

    Default Battery discharge problem

    Hi All,

    Iím new to this forum and certainly not a mechanic. I would be grateful of any help.

    I have a 2002 1.9DCI Laguna with a battery discharge problem. If I use the car daily it is OK, but if I leave it for 3 days it will not start (battery dead). This has happened twice over the last month (the car is usually used daily)

    The battery is 6 months old and below is the series of tests that I have carried out since the car would not last start - Monday 29/01/07.

    Monday: Would not start and tested the battery voltage = 9.17V.

    Tuesday: Jump started and drove 12miles to have battery/charging tested. Battery voltage after engine stopped left 30 mins = 12.68V. Voltage while engine running = 14.45V. Drop test OK. I found these results very surprising considering the battery had been charged from dead over a 30min drive? Put the battery on charge overnight.

    Wednesday morning (today): Took the battery off charge and measured the voltage = 12.96V. Tested for parasitic drain using DMM on 10A scale connected in-series with the negative terminal. The reading was initially 1.5A but fluctuated for approx 15secs to read a constant 30mA (could the initial fluctuation be the computer switching on with the resistance of the DMM?) I suspect this reading is acceptable, but wonder whether it is accurate as the reading settled without fluctuation. Would you expect the DMM to give an exact reading as this, or should it fluctuate slightly?

    Anyway that is the limit of my knowledge and would appreciate any help on how to fix this problem.

    Kind regards,
    tommo

  2. #2
    Join Date
    Oct 2006
    Location
    Sussex
    Posts
    1,824

    Default

    Some vehicles can take up to 45 minutes to shut down. The reading you should get is 0.03 amps. So were you getting 0.03 or 0.30 on your meter? If it was 0.03a then this is ok if it was 0.30a then this is too high and you will need to start pulling fuses to isolate each circuit.

    HTH
    Last edited by Sussex Patrol; 04-03-08 at 22:08.

  3. #3
    Join Date
    Jan 2007
    Posts
    5

    Default

    Thanks Matt.

    The reading was 0.03 after about 15 secs. Took the car to another garage for tests which indicated battery/charging OK and no current drains at that time.

    Measured the voltage this morning = 12.2V. Is this a reasonable reading after being left overnight?

    The only thing I can think is a relay occasionally holding on when the engine is stopped. What do you think and how do I progress if it is an intermittent fault?

    Really fed up with this car, electrics and suspension are rubbish and I've never experienced as many niggly faults in a car.

    Any help appreciated - Ian

  4. #4
    Join Date
    Mar 2007
    Posts
    24

    Default Battery Discharge Problem

    I had that on a car once, the battery would drain overnight, I checked that I had not left any lights on or anything.........................Finally found the problem..................it was the car radio, the memory circuit was draining the battery, I replaced the radio and the problem never happened again.

  5. #5
    Join Date
    Oct 2007
    Posts
    3

    Default Battery Discharge

    I have the same problem with a new Passat. Battery discharge to point where the car will not start after 3 or 4 days. Dealer has not been able to trace fault. Their readings were 0.50ma pulsing and after replacing the OSF door control module and onboard power supply unit it was down to acceptable 0.03ma. Despite this the problem persists and they eventually replaced the battery. This has not worked also and I am back to square one and chasing the dealer to make further investigations or replace the car. Point of interest, it was fitted with a VW radio/sat nave, tow bar and rear sensors before delivery to me.

  6. #6
    Join Date
    Feb 2007
    Location
    scotland
    Posts
    297

    Default

    tommo please check your boot light , see if its warm when the car has been stood for a hour . i have had quite a few cars with that problem and even with our amp clamp around the wire , it was not showing . but the boot light was on ...

  7. #7
    Join Date
    Oct 2007
    Posts
    11

    Default

    With the discharge your saying i would fit new battery. I cant see the fault being due to drains. Also if you have ever totaly flatened your battery it will need more than one night charge to restore it. I have seen totaly flat batterys take a week to recove and some never do or dont recover on all cells.

  8. #8
    Join Date
    Oct 2007
    Posts
    3

    Default Battery Discharge

    Many thanks for the comment. The car is back with the dealer now for further checks. The battery indicator was not green despite having been replace 2 months ago. My suspision is that the drain on the battery is progressive over time and eventually gets to the point were a few days standing finishes what charge there is off. When and if I get more than a pat on the head from the dealer I will post it for all to share.

  9. #9
    Join Date
    Oct 2007
    Posts
    3

    Default Passat Battery Drain

    They never found the problem with mine after 5 weeks of trials eliminating various parts (sat nav, radio, towbar, proximity sencors).

    They estabilished that something was kicking in after about 8 hours and progressively draining the battery. My suspician was the radio TP which records traffic messages or the sat nav aerial.

    In the end they arranged a no cost exchange for a new Passat which has behaved so far fine.

  10. #10
    Join Date
    Oct 2006
    Location
    Sussex
    Posts
    1,824

    Default

    Symage- as yours is a different vehicle I have asked admin to start a new thread for you

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