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Thread: AGM Battery Problem?

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    Senior Member Mark55's Avatar
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    AGM Battery Problem?

    Hi
    I have a 2015 Golf SV 2.0 TDI DSG, it has a Varta AGM 7PO-915-105 12v 68ah battery.
    Over the last week I have been checking the State Of Charge (SOC) of the battery first thing in the mornings and it reads around SOC=40%

    A typical weekday drive is 30 miles with 200+ at weekends.

    I fitted a battery charger with an AGM setting and digital readout, the first reading was 11.6 volts and 2 bars on the state of charge.
    After 4 hours on charge the reading was 13.8 volts and all 5 bars light up, the SOC was now 90%

    Is this OK, or should I replace the battery?

    Or get the dealers to check the battery and alternator out?

    Thanks in advance.
    2015 Golf SV SE 2.0 TDI-CR, DSG, Stock

  2. #2
    Administrator Keithuk's Avatar
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    What are you using to check the state of charge? There is no device that I know of that shows the state of charge, a volt meter only shows voltages. To check how good a battery is you need to load test it to simulate cranking for 15 seconds and note the battery voltage. A petrol engine shouldn't drop below 9.6v, a diesel engine 10v.

    What's the charging rate of your battery charger?
    2010 Golf GTD (170) CBBB, 5 Door, Shadow Blue (P6/D5Q), Transmission Code: KXZ, Flat Tyre Indicator, Basic Protection Pack + VCDS.


  3. #3
    Senior Member Mark55's Avatar
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    With the ignition off.
    Hold down the trip reset button, on my SV it's in the middle of the dase.
    The screen above the button will show time then battery, when battery showing release the button.
    The screen will then show SOC "State of charge" of the battery.
    2015 Golf SV SE 2.0 TDI-CR, DSG, Stock

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    My impression of the battery management systems on recent VW group cars is that they are a bit inadequate, and batteries are not getting charged sufficiently.

    Keep monitoring the SOC each morning, if it tends to decrease as the days go by since the last charge with your charger, get battery and charging system checked. It's quite possible that your battery is nearing end of life, which is a shame, as they should last a lot longer if the car looked after them properly, particularly in view of your driving patterns.

    State of charge can be fairly accurately assessed from resting voltage alone. The problem with that is that the battery in a car is never truly resting (i.e. no current flowing out of it) due to all the electronics, so the battery management system has to make assumptions to 'guess' a figure. See: https://batteryuniversity.com/learn/...tate_of_charge
    Last edited by Pete1; 22-10-18 at 09:58.
    My car: 2003 Polo 1.4 BBY, Petrol
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    Administrator Keithuk's Avatar
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    That's new technology for you, some thing are good some things are crap. The old method for checking a battery state of charge is with an Hydrometer as it shows in Pete's link.

    Modern batteries you can't remove the cell top up plugs (only look at the bubble colour) as they are maintenance free.

    What's the mileage of your 2015 Golf SV? I'm still on the original battery, I do have to top it up with my charger in Winter because I don't do the mileage I used to.
    2010 Golf GTD (170) CBBB, 5 Door, Shadow Blue (P6/D5Q), Transmission Code: KXZ, Flat Tyre Indicator, Basic Protection Pack + VCDS.


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    Senior Member CJJE's Avatar
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    That's an interesting 'Easter Egg' you've revealed, Mark!

    I've just tried it on my SV and got a 70% reading, so it sounds worth getting your battery/alternator checked out

    I've done around 36,000 miles on my 3 1/2 year-old SV, with a mix of long summer journeys, 100 mile trips on occasional weekends, short trips to the shops, and sitting unused on the drive.

    Chris
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    Senior Member Mark55's Avatar
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    Hi
    Have booked the car in at the VW dealers later this week. The service guy seems to think the car will need a new battery. So much for the greater life span of the AGM battery type, if a new one is fitted the old one lasted just 4 years.
    2015 Golf SV SE 2.0 TDI-CR, DSG, Stock

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    Quote Originally Posted by Mark55 View Post
    Hi
    Have booked the car in at the VW dealers later this week. The service guy seems to think the car will need a new battery. So much for the greater life span of the AGM battery type, if a new one is fitted the old one lasted just 4 years.

    Interesting comment about AGM batteries at the end of this page: https://batteryuniversity.com/learn/..._glass_mat_agm

    "AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49C (120F)."

    Engine bays, and thus battery cores could easily be at >49C for anyone who does anything other than local runs, especially in the summer, I would've thought.
    My car: 2003 Polo 1.4 BBY, Petrol
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    Senior Member Sam&Anne's Avatar
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    Quote Originally Posted by Mark55 View Post
    Hi
    Have booked the car in at the VW dealers later this week. The service guy seems to think the car will need a new battery. So much for the greater life span of the AGM battery type, if a new one is fitted the old one lasted just 4 years.
    Seem to remember Crasher stating recently that the much loved start/stop system will ultimately have an adverse effect on various components, the battery being one of them.
    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!

  10. #10
    Administrator Crasher's Avatar
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    All of a sudden the trend we have seen now for years where a battery would last a decade or more has gone, the funny thing is this started to become apparent about the same time early gen2 stop/start cars came out of warranty, apparently the mood is buoyant in the battery and starter motor replacement industry, they have not seen such business in living memory. In the early 80’s VAG brought out a few cars with SSA, stop start automatic. This was abandoned within a few years due to the huge increase in warranty claims on starters, alternators and batteries. If you think AGM battery life is crap at about four years, wait until lots of you (not in this life, me) are driving around in electric cars which need a new battery at seven years, yes better you say but at 10000 plus fitting, that is if the car hasn’t incinerated you first...

    https://www.theguardian.com/technolo...ot-mode-report

    https://www.abc.net.au/news/2018-05-...nagers/9747648

    This isn’t restricted to Tesla, Lithium Ion batteries are a crazy solution to a problem that does not exist

    https://www.motortrend.com/news/byd-...an-gtr-211017/

    Just down the road from where I live and it happened again last week

    https://www.bbc.co.uk/news/uk-englan...shire-36401455

    We are going down another crazy ill considered diesel disaster type road again and still no one can tell me what the authorities are going to do in 20 years time with millions of tonnes of discarded batteries, it is as insane as Elon Musk!
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