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Thread: Can you fully disconnect the battery when changing it?

  1. #1
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    Can you fully disconnect the battery when changing it?

    Hi all, my original battery on my 2013 Golf is starting to give indications it is on its last legs and my experience with sudden battery failures, I have decided to swap in a new one. I have ordered a OBDEleven which should be here next week so I can update the coding and will probably get the Century DIN65LH AGM battery, which I can get locally at a decent price.

    I read in a few places, that the BCM module on the negative terminal should be kept powered on while doing a battery change. Do I really need to keep it powered? Seems a bit overkill to me.
    Last edited by flagger; 10-07-2018 at 02:51 PM.

  2. #2
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    There's no need to keep power on, though you'll have to clear the fault codes and restore windows anti pinch feature. If you have s/s system you will also need to code the new battery in.

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    Thanks for the quick reply Transporter. That's good I guess, I am used to dumb battery systems. So the car will throw some faults on first start up after the new battery is in? I assume that I can just clear the codes straight away with the OBDEleven. Did not even know about the windows anti pinch feature. I hope that is programmable with the OBDEleven too.

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    You just roll the windows down one by one, continuously while holding the window switch and up the same.

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    Ahhhh, thank you! Would not have known that about the windows thing.

  6. #6
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    wind down and hold for 5 secs. wind up and hold for 5 secs
    that should let the system learn the settings
    Tig 162 R-Line; Audi TT

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    Quote Originally Posted by flagger View Post
    Hi all, my original battery on my 2013 Golf is starting to give indications it is on its last legs and my experience with sudden battery failures, I have decided to swap in a new one. I have ordered a OBDEleven which should be here next week so I can update the coding and will probably get the Century DIN65LH AGM battery, which I can get locally at a decent price.

    I read in a few places, that the BCM module on the negative terminal should be kept powered on while doing a battery change. Do I really need to keep it powered? Seems a bit overkill to me.
    Sorry to bring up old thread. I just replaced with same battery. Did you end up coding it? Just wanted to know what details to enter such as serial, manufacture etc as century doesn’t have bem details. I have stop start system btw.

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    @xradioactiveman: hmm........ given the age of the post that you have included, you might not get a response from @flagger. I've just read this thread and there appears to be a number of mis-understandings in the questions/responses. (BCM isn't connected on the negative terminal- and the module that is on the negative terminal (J367) doesn't need to be separately powered when replacing battery)

    As for your specific questions, if your new battery doesn't have a BEM sticker, do this:
    • Battery adaptation-Rated battery capacity > change to capacity of new battery
    • Battery adaptation-Battery technology > change to "FLEECE" for AGM (I assume this is the technology for your "century" battery - as per OP)
    • Battery adaptation-Battery manufacturer > not important
    • Battery adaptation-Battery Serial Number > actual number not important - it's just necessary that the number is different to existing value (suggest you change anyone of the digits to another number)


    Don
    Last edited by DV52; 09-10-2021 at 10:40 AM.
    Golf MkVII 103TSI (Highline) my13
    Polo 6R 77TSI (Comfortline with Comfort Pack) my14

  9. #9
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    Quote Originally Posted by Williamsheikspare View Post
    Its a great idea to replace your battery as soon as possible.
    But only when it needs to be replaced, typically when it won't hold a decent amount of charge even when placed on a charger for a long enough time (which can be many hours if the charger can only supply a small amount of charge).

    The best way to test a battery is with a true load tester (like a 12V toaster that produces a lot of heat while testing) after the battery has been fully charged.
    2017 MY18 Golf R 7.5 Wolfsburg wagon (boring white) delivered 21 Sep 2017, 2008 Octavia vRS wagon 2.0 TFSI 6M (bright yellow), 2006 T5 Transporter van 2.5 TDI 6M (gone but not forgotten).

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