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Symptoms of a dying car battery?

tquattro Jan 10, 2020

  1. tquattro

    tquattro Registered User

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    Hi,

    I noticed lately, that if I turn on the rear window defroster, the defroster relay starts to continuously click(on-off-on...) until the engine gets warm. I also noticed that the heated seats don't heat up as much as they used to while the relay clicking happens. A couple of days ago, I realised that if I turn off the Auto Supplementary Heater(the electric one, not the stationary fuel based one), as this is has a high current draw, the defroster and the seats heating work as they should. The supplementary heater shuts off automatically when the engine is warm, so this explains why the clicking stopped after driving for a while. This looks like some kind of current draw management thing.

    No side effects other than the ones above that I can tell of. The car started without a sweat at -9C after sitting for 24+hours. Battery SoH appears to be at 85%.

    The alternator seems fine, it has a 14.8 - 14-9V charge(this is not too much for an AGM battery). On a friend's mk7 Golf, after startup the charge current is also at 14.8-14.9V, but on his car the charge drops to 14.4V after a couple of minutes(tested this with everything turned on: heated seats+steering wheel+mirros, rear defroster, supplementary heater...). On my car it takes 15-20min to drop to 14.4V.

    Could this be a dying battery or it could be something else? The battery is 5years old, the OE one.
     
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  3. Flying Scotsman

    Flying Scotsman Registered User

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    Battery life on OEM battery is 2-4 years, and 5 years is really pushing it.
     
  4. eribaMotters

    eribaMotters Registered User

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    I've been driving since 1982, selling cars on at between 3 and 10 years old. I've needed to replace only tow batteries, both at about 8yrs. I'd be well cheesed off if a battery only lasted 2-4 years.

    Colin
     
  5. Flying Scotsman

    Flying Scotsman Registered User

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    I also was blown away that the OEM battery has such a short life....owners on this forum have had to replace in some cases under warranty at 2-3 years. Also note that some dashcams are notorious battery eaters
    From Audi.
    The lifespan of an Audi car battery will vary. In general, you can expect any car battery to last at least three to five years. Properly caring for your battery can extend its life, but it is normal to have to replace a battery every three years. If you want to be proactive about avoiding battery problems, it won't hurt to simply replace the battery on a regular schedule rather than waiting for signs of failure or risking being stuck far away from home because your car won't start.
     
  6. AlS3BE

    AlS3BE Registered User

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    EFB and agm batteries are designed for stop start engines so have good ability to work in a low charge state and constant on/off charge cycles. While they are good they do seem to have a shorter life span compared to old school lead acid batteries.
    Agm batteries are meant to be better than EFB. Was told by the AA guy that came out to my flat said that he was condemning EFB batteries a lot more than the agm’s. His recommendations was replace mine with agm he has in his truck till I told him my car was a year old and going back to Audi for warranty.
     
  7. rcnacura

    rcnacura US Spec 8V

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    I don't have start/stop, but this platform seems to consume battery voltage more than it can produce. This causing the premature battery failure.

    To me the car needs a 48V system.

    On my third battery in 5 years and the car is already showing signs this battery isn't lasting that long too. Luckily aftermarket and the warranty is great so I can get replacements if needed.

    Sent from my Pixel 3 XL using Tapatalk
     
  8. msdmjb

    msdmjb Registered User

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    My S3 battery was over 5years old and regularly left for 4-5weeks at a time, never had any issues but never used start stop.
    Only way to really test it is to see the voltage drop when cranking.........even a knackered battery can show >12v at rest.

    If it coped with -9 cold start then realistically it sounds quite healthy, i reckon with the additional heater it is just drawing too much when everything else running. I would just make sure it gets a run when the heater is off to make sure it gets a good charge.
     
  9. AlS3BE

    AlS3BE Registered User

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    thats the other problem. In order to reduce fuel consumption they reduce the alternator load on the car. Then there’s tech like recuperative braking which essentially puts a big alternator load when you are using engine braking. Problem with that is the battery is never charged to a high state of charge like 90+% it’s constantly around 70-80% so in the winter months with heated windows and seats and everything turned on it can struggle a little to get back to a good state of charge. Fine if you do long journeys but a not so good if you do shorter journeys.
     
  10. tquattro

    tquattro Registered User

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    Before ordering a new battery, I tried the battery from a mk7 Golf of a friend(identical battery, but newer, and no similar issue on his car - both cars 2.0TDIs). The symptoms were the same on my car with that newer battery.
    Maybe there's an issue with my electric heater and it draws more current than it should?
     
  11. AlS3BE

    AlS3BE Registered User

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    problem with testing this way is you aren’t coding the car for a different battery.
    When a new battery is fitted then coded the charging characteristics changes and continuously changes as the battery ages. So as it gets a few years older it won’t charge it beyond a certain point. By borrowing another battery the car will still think the old battery is there so will charge it to the same state and in the same way.
     
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  13. tquattro

    tquattro Registered User

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    I know about the coding, I changed the battery serial. So this isn't the case.
    Could it be a Coding/Adaptation issue? Last year I upgraded my CAN gateway's firmware to fix some issues after the MIB2 retrofit. I noticed that in the new firmware has some extra adaptations lines, the last one from bellow stands out to me(the gateway coding and the rest of the adaptations are the same as before):
     
  14. AlS3BE

    AlS3BE Registered User

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    don’t have a clue about the coding/adaptation there. have you checked the charge state in live data? After a long drive it should be 80%+ if not 90% for a healthy battery. When mine started dying eventually refusing to start the car it showed around 65-70% after a 2 hour drive and overnight dropped to around 50-55%. My new battery shows around 85% after a 20min drive and maintain around 80% overnight. Only thing I have running is my 2ch dashcam overnight.
     
  15. tquattro

    tquattro Registered User

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    Charge state is at around 85%. Also, all the quoted adaptations from the my previous post, were not present in my original gateway firmware.
     
  16. AlS3BE

    AlS3BE Registered User

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    newer modules are all done by adaptations not long coding so that could be the difference between your old and new module.
    Charge state at 85% is pretty good so will look at something else. Could be faulty relays or a short somewhere
     
  17. NHN

    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    Pulsing on & off isn't unheard of when the cars load is high, that's not to say there isn't an adaption issue, but the fact it stops when the cars warmed up hints to me it's working logically.

    I'd be interested to see if an Audi visit corrects this via either a default download to modules or firmware update if available.

    Have you tried another relay, checked the relay for buildup, I've had some that needed the contacts dremeled back to shiny metal to restore the normal conductivity, although on a car of your age it probably isn't a relay issue tbh, just maybe by design.
     

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