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Changing Battery in a 08 TDI 170

Discussion in 'A3/S3/Sportback (8P Chassis)' started by chinnyhill10, Mar 12, 2013.

  1. chinnyhill10
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    chinnyhill10 Member

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    Hi,

    I know I need the Varta Silver Dynamic E44, but how straightforward is it to change the battery?

    Changed batteries before in older cars but not in a car with all sorts of modern electronics. A mate told me when he did his, his dash lit up like a Christmas tree.

    Easy to do? Any problems or things to watch out for? Or even better, is there a howto guide online?

    Thanks.
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  2. NHN
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    NHN Modmetractor

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    Just swap over, take for a short drive & any lights should disappear.
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  3. chinnyhill10
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    chinnyhill10 Member

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    Cheers. Will probably tackle this over the weekend one I find a socket extension long enough!
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  4. chinnyhill10
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    chinnyhill10 Member

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    Just to update, the battery went in fairly easily. Even someone as ham fisted and non-car minded as me managed it. I've done batteries before but only in older less complex cars which have more room to work in and far less electronics attached.

    The Varta is slightly larger than the stock battery but fitted into the existing bay easily (in fact the box comes apart which makes things easier). Took a small amount of jiggling to get it to sit right. Then bolted it back down and job done.

    Not very scientific but the car started easier, but also I used a volt meter plugged into the lighter socket to see what it was doing when cranking. Before the voltage would sink down to 8v when the engine was trying to start. This time it was measuring 10.5v at its lowest and thats before its even been fully charged.

    Managed to reset 3 of the windows straight away. The 4th needed me to cycle the ignition again after the test drive and then it was fine.

    Job done. Good news was that the Varta actually worked out cheaper delivered than many inferior batteries as well. 69 quid which included next day delivery. The retailer also include a handy fact sheet which helped an idiot like me know that I had to remove the safety caps etc:

    E44 Varta Silver Car Battery 77Ah (577400078) - Car Batteries - Varta Car Batteries

    One weird thing. When the battery was unplugged the car lost the time, but not the date!
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  5. Sidhu88
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    Sidhu88 Active Member

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    Depending on how long you have the battery out the ecu still manages to retain some power and wont fully reset until its fully discharged all power from the system. Usually takes 30mins plus for this to happen. Also, 10.5v is still quite a low reading. Maybe because u were testing thru the cig lighter it showed less but from experience and with the engine running u shud be getting anything between 13-14.7. If ur getting lower than that then ur alternator needs replacing as its not putting out enough power. If this is the case then chances are ur old battery may have been ok but the alternator wasnt charging it enough
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  6. chinnyhill10
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    chinnyhill10 Member

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    I said it was dropping to 10.5 during cranking, not during running. Why on earth would the voltage increase ABOVE the actual battery capacity before the engine has started? Also, as stated, the battery may not be fully charged as yet anyway.

    Every battery is going to drop during the cranking period as that is the second or so when the battery is under maximum load before the car fires up. My problem with the old battery was slow starting, presumably because it was dropping as low as 8v.

    When it starts running the voltage then jumps up to approx 14v. But it did that before.
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  7. Sidhu88
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    Sidhu88 Active Member

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    Fair enough, i misread the bit about it being when u were starting the car. Also your presumptions would be correct, pretty obvious no?
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