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Thread: Battery problem?

  1. #1
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    Battery problem?

    Hi

    Just came on here looking for answers to a few questions, one being the state of my battery. Found the AGM battery thread (https://www.volkswagenforum.co.uk/sh...ad.php?t=31615) very useful but don't want to clog it up with my query as I'm no mechanic and so am not 100% sure it is battery rather than some other part of electrical.

    I often switch the start/stop off and majority of mileage is on motorways or A roads rather than urban stop/start conditions but starting last autumn I found stop/start wouldn't run when previously it would have done (eg at the end of an hour long, mainly motorway, drive) and idle revs have often been higher than they used to be (previously only noticed a couple of time when found DPF was doing a regen) and seem inconsistent. For example, start car, idles at usual (800ish), end of journey idling has gone up to well over 1k, or I'll be stationary in traffic and idling will rise to 900ish. I also started paying attention to the voltage shown on VW Connect and taking screenshots end of '18 and they seem erratic to me (eg often 15.1V at start or end of a trip but then had plenty in the range 12.3-13.5V at the end of trips of say 20ish-30ish miles mainly along a motorway. Lowest seen was 11.8V).

    The engine usually takes, I'd guess, a couple of seconds for the starter motor get the engine going when the car hasn't been used for a few hours but a couple of times in the past couple of weeks it has done this but then immediately flipped back to the starter motor again for another second or two, catching properly the second time.

    I've also noticed recently that start/stop when enabled, would not trigger if the aircon/fan was above a certain speed. This is with nothing plugged into USB, lights on 'auto' but bright daylight, media/display turned off, no rain and car dones't have sat nav (ie minimal possible other load). Back in December, dial turned to some degree of heating, fan at 3 or above would mean no start/stop, turn to 2 (my normal, leave at almost all the time setting) engine would switch off, turn fan back up to 3 engine would turn on. By last week, similar temp on the dial, similar distance driven, I'd guess similar external temp, fan at any setting would mean engine wouldn't turn off but if I turned the fan off the engine would turn off and if I then turned the fan back to 2 the engine would stay off.

    So had a mechanic check the battery and he told me it was 46% and would last 1-2 more months. FWIW, after reading in the AGM thread about the hidden SOC check I tried it but all I get is __ %, so guess I'm not doing it right (got in car, simply pressed trip, key not in ignition).

    Does this sound like the battery failing or something else?

    For some background, the car is a mid '15 build, '16 reg 1.6, less than 20k miles. Until mid '18 I could count on one hand the number of times I used the car locally. All use was for at least half an hour or so and on roads where would be doing 60mph or above for a few minutes at least every journey. Since mid '18 has done more but still less than once per week on average short local use (3 or 4 legs of 1-3 miles). Car is used sometimes 3 or 4 days per week, sometimes not for a week or more. Averages probably twice per week through the year, most journeys 1 hour or more and involve a large percentage on motorways or fast A roads. Not normally garaged.

    I vary use of start/stop but I haven't used it much. Obviously not happening on any free flowing M or A, car hasn't done much short local driving etc. and a lot of the time I switch it off when I start the car. Aim for it to be used only when looks like will be stopped for 15 seconds or more. So car hasn't done a lot of starts for the mileage. Barely ever use the radio/media and probably been used while the engine isn't running for less than 1 hour in total. No Sat Nav, so more often than not will have phone plugged into USB but do this after the engine started and don't leave anything plugged in to USB when the engine isn't running. Alost always had the lights set to Auto as this is what the dealership recommended. Usually make sure wipers stalk set to off when leave car but on occasion have forgotten and left it set to auto.

    Appreciate any advice.
    Last edited by IfEverythingWasAsReliable; 10-02-19 at 13:01. Reason: added VW Connect voltages
    2016 Golf SV 1.6 TDI-CR

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    Administrator Crasher's Avatar
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    We are beginning to suspect that the reliability of AGM batteries is not all it is supposed to be.
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  4. #3
    Senior Member Sam&Anne's Avatar
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    Quote Originally Posted by IfEverythingWasAsReliable View Post
    Hi

    Just came on here looking for answers to a few questions, one being the state of my battery. Found the AGM battery thread (https://www.volkswagenforum.co.uk/sh...ad.php?t=31615) very useful but don't want to clog it up with my query as I'm no mechanic and so am not 100% sure it is battery rather than some other part of electrical.

    I often switch the start/stop off and majority of mileage is on motorways or A roads rather than urban stop/start conditions but starting last autumn I found stop/start wouldn't run when previously it would have done (eg at the end of an hour long, mainly motorway, drive) and idle revs have often been higher than they used to be (previously only noticed a couple of time when found DPF was doing a regen) and seem inconsistent. For example, start car, idles at usual (800ish), end of journey idling has gone up to well over 1k, or I'll be stationary in traffic and idling will rise to 900ish. I also started paying attention to the voltage shown on VW Connect and taking screenshots end of '18 and they seem erratic to me (eg often 15.1V at start or end of a trip but then had plenty in the range 12.3-13.5V at the end of trips of say 20ish-30ish miles mainly along a motorway. Lowest seen was 11.8V).

    The engine usually takes, I'd guess, a couple of seconds for the starter motor get the engine going when the car hasn't been used for a few hours but a couple of times in the past couple of weeks it has done this but then immediately flipped back to the starter motor again for another second or two, catching properly the second time.

    I've also noticed recently that start/stop when enabled, would not trigger if the aircon/fan was above a certain speed. This is with nothing plugged into USB, lights on 'auto' but bright daylight, media/display turned off, no rain and car dones't have sat nav (ie minimal possible other load). Back in December, dial turned to some degree of heating, fan at 3 or above would mean no start/stop, turn to 2 (my normal, leave at almost all the time setting) engine would switch off, turn fan back up to 3 engine would turn on. By last week, similar temp on the dial, similar distance driven, I'd guess similar external temp, fan at any setting would mean engine wouldn't turn off but if I turned the fan off the engine would turn off and if I then turned the fan back to 2 the engine would stay off.

    So had a mechanic check the battery and he told me it was 46% and would last 1-2 more months. FWIW, after reading in the AGM thread about the hidden SOC check I tried it but all I get is __ %, so guess I'm not doing it right (got in car, simply pressed trip, key not in ignition).

    Does this sound like the battery failing or something else?

    For some background, the car is a mid '15 build, '16 reg 1.6, less than 20k miles. Until mid '18 I could count on one hand the number of times I used the car locally. All use was for at least half an hour or so and on roads where would be doing 60mph or above for a few minutes at least every journey. Since mid '18 has done more but still less than once per week on average short local use (3 or 4 legs of 1-3 miles). Car is used sometimes 3 or 4 days per week, sometimes not for a week or more. Averages probably twice per week through the year, most journeys 1 hour or more and involve a large percentage on motorways or fast A roads. Not normally garaged.

    I vary use of start/stop but I haven't used it much. Obviously not happening on any free flowing M or A, car hasn't done much short local driving etc. and a lot of the time I switch it off when I start the car. Aim for it to be used only when looks like will be stopped for 15 seconds or more. So car hasn't done a lot of starts for the mileage. Barely ever use the radio/media and probably been used while the engine isn't running for less than 1 hour in total. No Sat Nav, so more often than not will have phone plugged into USB but do this after the engine started and don't leave anything plugged in to USB when the engine isn't running. Alost always had the lights set to Auto as this is what the dealership recommended. Usually make sure wipers stalk set to off when leave car but on occasion have forgotten and left it set to auto.

    Appreciate any advice.
    I have seen - % on the battery status several times but I take that with a pinch of salt.
    I have seen 50% after standing overnight and 70% after the following 200 mile run.
    Manual readings have always given acceptable results despite the car being idle for days at a time.
    No problems starting in any conditions (but mine is petrol)
    NEVER have used start / stop since day of purchase and never will. Destructive abomination IMO.

    In answer to your other posts related to brake discs, mine are certainly showing rust. First few minutes "cleans" them enough for the brakes to be fine.
    Re KeithUK - yes I also have the infernal EPB and hate it. Stuff your cupholders VW, give me a proper lever any day.
    2015 Golf SV SE 1.4 TSI, DSG. Limestone grey. Sat Nav. F & R parking sensors. RVC. Digital climate control. Fog lamps.
    Wife: VW UP!

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  6. #4
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    I guess I followed the procedure corectly then. Will see what the display shows after having driven it next.

    Not knowing your mileage etc. and guessing that the 70% means 30% loss since new (rather than 50%), that would seem like the % loss I'd expect on a 2015 car.

    With the brakes, I always expect to get surface spotting after not very long unused. The concern is that the issue disc is rough across a large % of the surface, looking as though pad/disc contact is limited to cleaning off the surface rust at most. To me I don't see how it can possibly be getting full braking contact as per design/intention.
    2016 Golf SV 1.6 TDI-CR

  7. #5
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    I think the % is the % of a full charge and not the 'wear rate' (ie using your 70% figure NOT the
    30% loss of chargable capacity 70% would infer.
    I expect 100% is not achievable as where would the regenerative battery charging go if
    it starts at 100%...if I understand it right.
    Correct me if I've got the wrong end of the stick!
    2014 Golf SV SE 1.4 TSI, 7A DSG

  8. #6
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    Maximum capacity at that stage of battery life is what I mean. So day 1 (battery manufactured and instantly installed in vehicle) would expect to see 100%, day final (battery no longer capable of starting vehicle) would expect to see 25% (as far as I understand it the minimum required, roughly), Sam&Anne's battery in a '15 reg at 70% (lost 30% of max so far out of 75% for usable life of battery).
    2016 Golf SV 1.6 TDI-CR

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