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Stop start battery

Discussion in 'General Mercedes-Benz Related Discussion' started by E500 Pete, Sep 27, 2019.

  1. E500 Pete

    E500 Pete Senior Member

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    Hi all

    I don't actually want to use the stop go function on my car but I have noticed that if I don't turn it off the symbol on the display stays amber and only goes green after a very long run.

    Does this mean that I have a battery problem and if yes, which battery?

    Not worried about it for the stop start but I am concerned that it might eventually effect other functions.
     
  2. rf065

    rf065 Senior Member

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    It could be either battery, if you have two, both need to be able to hold a full charge. It should not take a long run for it to go green either, but there are a host of other factors like temp ect, all play their part in the process.
     
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  3. Altamar

    Altamar Active Member

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    Hi, please see my thread below where I had the same problem with the stop start on my W212. Buying a new aux battery (which was in the boot on my car) solved the problem. I took the view I could buy the battery for under £50 online whereas it would cost me more than that in diagnostics and I would still have to buy the battery.

    https://forums.mercedesclub.org.uk/index.php?threads/stop-start-not-working.175488/
     
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  4. malcolm210

    malcolm210 Senior Member

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    Easy enough to test both batteries they should read 12.6V fully charged engine off (2.1V per cell).
    I replaced my main battery 4 months ago due to lazy starting and the Stop/Start ready lamp now comes on after 0.5 mile, previously it wouldn’t show Stop/Start ready at all. I also turn it off but it does double up as a good battery indicator
     
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  5. rf065

    rf065 Senior Member

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    Problem with this is at some point the second battery has been replaced with a capicitor which sits behind the glove box. So if you don't have an actual second battery on later models, I'm not sure how you can test the capacitor?
     
  6. malcolm210

    malcolm210 Senior Member

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    In which case it looks like the main battery is starting to fail mine was goosed at 7 years old and I hadn't seen a Stop/Start ready light for a couple of years
     
  7. rf065

    rf065 Senior Member

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    When my stop/start would not work, it was the capacitor that failed, but mine was replaced under warranty.
     
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  8. malcolm210

    malcolm210 Senior Member

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    That’s a new one on me I didn’t realise newer models had a capacitor installed and if this has failed once it may have failed again it would appear the car will need a STAR connection to test the capacitor
     
  9. OP
    E500 Pete

    E500 Pete Senior Member

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    Thanks for the help.
    I will try to find out if my car has a second battery or a capacitor, 2014 W222 S Class. It was easy on my old E class but under the bonnet on this is just a load of plastic covers.
     
  10. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    Could be

    or could be a few other reasons, most common is batteries, but lots of things will stop the system engaging.
     
  11. BillyBoy

    BillyBoy Senior Member

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    Just one to try - I used to have the same problem with my 212, and it was linked to the air con. If I turned the AC off, it worked perfectly,, turn it on, and the Eco almost never went green.
    My theory was that one of the criteria for start/stop not enabling is the AC is on and the windscreen misted. I think over time the refractive sensor that check this gets dirty or drifts from its initial tolerance and therefore"thinks" the windscreen is misted even when it is not and therefore will not let the start/stop kick in with the AC on.
     
  12. OP
    E500 Pete

    E500 Pete Senior Member

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    Interesting thought, I'll give it a try next time I'm out.
     
  13. OP
    E500 Pete

    E500 Pete Senior Member

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    Tried it with the AC off for a run of about 15 miles mixed traffic yesterday and the light still stays amber. Thanks for the idea anyway.
     
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  14. ajlsl600

    ajlsl600 Senior Member

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    possibly another sensor headache . my latest motor uses the mk 1 eyeball sensor,screen misted ,put heater on ! cant see ,get a cloth .simples these days sensor seems to mean 2 things , looming headache and inevitable wallet shrinking.
     
  15. OP
    E500 Pete

    E500 Pete Senior Member

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    Thanks for all the ideas.

    Interestingly I had the Mercedes Me adaptor set up today and it shows the battery at 71% which the guy who was setting it up said "looked fine". I would have thought it should be in the 90% area at least so it is probably that the stop start wants to see more than 71% which makes sense.

    I will wait until next time it goes green and have a look at the battery percentage. Wait for the next exciting episode.
     
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