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Stop start battery voltage.


68vitesse
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My modern car 13 Plate Audi A3 with stop start on occasions when I turn ignition on comes up with the message battery voltage low will charge while driving. Just checked voltage, car not started for more than a day, just below twelve volts while the one in the Vitesse is over twelve.

Anyone know if this is normal for a stop start battery, battery is the original one so coming up to six years but only 28000 miles.

Many thanks

Paul

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Paul,

Whatever makes you think that a warning from your car's OnBoard Diagnostic system could indicate a "normal" condition?

The Battery Management System has detected something out-of-spec, in this case a low battery voltage, which could be - probably is - an indication that your battery is nearing the end of useful life.  After less than 5000 miles/year, it will have done a LOT of short trips, starts when cold and stop-start events   As your car is one that has automatic stop-start when stationary. it needs a specialised battery, and probably that the volts must be maintained to the car while a new one is fitted.    Don't just disconnect the old one and put the new one in!   You could lose all sorts of important functions, in particular the car security settings that would lock you out.

Of course, the charging system may be at fault, there could be something as simple as a loose/worn fan belt, or a failing alternator.   The OBD can be very stupid!    Do you have a multimeter,  to check the volts while running that should be about 14V?

John

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Thanks, had assumed voltage for an AGM battery would be the same as older style, usually turn the stop start off as I find it a pain in slow traffic.

The motor accesory store just down the road quoted £200.00 for new battery and to tell the computer, will have to get more quotes.

Thanks

Paul

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I have stop/start on my Polo GTI but I always hit the disable button as soon as I start the car so it never comes into operation.  My battery appears quite healthy but it is only three years old.  It appears to hold a charge well even when the car is unused for several months, unlike it's Mazda and Toyota predecessors which failed to start after three weeks lack of use.

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The volts for an AGM are the same, it's ability to withstand the stresses of use are greater.   But not infinite.      A quarter of a million stop-starts is quoted; seems a lot, but....

The purpose is not economy, but emissions, and the 'disable' button is  but a sop to 'customer empowerement'!    If you don't use it, you might as well have a good old wet acid type.   Which is a multiple pack, of six cells, just as the Absorbent Glass Matt battery is, except that has the acid in a gel on yards of matt, interleaved with with lead electrode sheets

AGMs are not cheap.    Halfords quotes about £100, plus fitting.

J.

PS a conventional battery should hold its charge for more than three weeks.   If not suspect a small drain even when ignition off - a fault, the radio, clock, security, etc.  Boot light on when closed is a favourite!

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A lot of modern cars charge at over 15V these days - can cause havoc with some 3rd party accessories if they are expecting a max of 14V (Though to be fair rare nowadays!) 

And things like radio's are coded to the car via the VIN number so swapping a battery in that sense is not an issue, but you do need to tell the battery management system you have changed it so it can reset to a clean start.

One of the first things I did on my BMW was buy a diagnostic tool to turn off the stop-start function by default - as i have probably said before, I find it dangerous in an auto as it will stop the engine as soon as you get to say a Tee junction - just when you are about to pull away. And whilst it might be better for the environment in the short term, I am not convinced that the extra wear on the engine and associated peripherals is good long term. 

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The 12 volt reading is what we term an open circuit reading and does not give a true indication of the batteries condition, it needs to be loaded. There are battery test boxes that place a load on the battery to test it.

However, the best test is "Does it start" as this is placing a large load on the battery. If it starts OK and is being charged then I would say it's not the battery. To check the charging run the engine and check the battery voltage reads around 14.5 volts.

Dave

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These stop start batteries are a minefield.............A neighbour with a Toyota Yaris got various prices from local garages varying from £120  to  £273..... He thought "oh dear"  I suggested, have you tried the main dealer?  Result was £59.05p inc vat. (fitting was dearer than battery) He bought one and fitted it himself :)  This does happen from time to time that the dealers are cheaper by a long way.... I dont know why though??

Tony.   

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20 hours ago, 68vitesse said:

Thanks, had assumed voltage for an AGM battery would be the same as older style, usually turn the stop start off as I find it a pain in slow traffic.

The motor accesory store just down the road quoted £200.00 for new battery and to tell the computer, will have to get more quotes.

Thanks

Paul

https://www.ebay.co.uk/itm/096-100-START-STOP-AGM-72AH-Heavy-Duty-12V-Car-Battery-More-power-than-AGM-EFB/292253931614?fits=Car+Make%3AAudi|Model%3AA3|Cars+Year%3A2013&hash=item440bb1185e:g:5wMAAOSweZJaKQwd:rk:2:pf:1&frcectupt=true

This is a better price Paul, Should you need one?  

Tony.

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They may not be the future.    The Smart Idle Stop System Mazda system indexes the pistons when it stops, and then injects fuel (Direct Fuel Injection) and sparks the appropriate cylinder, to restart the engine.    The conventional starter is not used, the engine starts more quickly and Mazda claim that drivers may not notice that their engine has been stopped.

The idea was introduced in anticipation of the Euro 5 standard in 2009.   This and its predecessors uses a standard cycle of driving, tested on a rolling road, which was of course the way that VW managed to cheat, as the ECU detected that only one pair of wheels was moving.    The cycle includes stationary episodes, so stopping the engine is a way of 'cheating' legally by having less fuel consumed and less emissions over the test.     

As this is a Euro-test, turning it off is an ideal way for Brexiteers to demonstrate that they are freespirit, individualist rebels, not smarmy conformists.  So there!  Take that, losers!

JOhn

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34 minutes ago, JohnD said:

As this is a Euro-test, turning it off is an ideal way for Brexiteers to demonstrate that they are freespirit, individualist rebels, not smarmy conformists.  So there!  Take that, losers!

I didn't like start/stop way before Brexit came along :)

My daily is german, SWMBO's is Japanese, my youngest is French and obviously I have British with the Spitfire.

So I embrace the world. Just don't want to have the Europeans telling me what rules I have to obey with - even if I might choose to obey them.............

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Did use the car today voltage dropped to just over seven volts when cranking then up to just below fifteen at tickover. Battery currently on charge, correct type charger set to two amps, not intending to drive car for next few days so will check voltage at intervals to see what the voltage drop is.

Thanks for the links to cheaper batteries, as to main dealer prices when l needed a tyre they where the cheapest.

Regards

Paul

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Hmmm. Cynical about all the technology in modern cars, brilliant when it works, a costly nightmare when it fails. My late father gave his 56 plate micra to my daughter in 2016 with 16000 miles on the clock. Within a year the lambda sensor after the CAT caused the engine warning light to come on. Cost £200 to have it replaced and the CPU reset. What a world we live in when the protection warning devices cost more to replace than the components themselves - when will it all stop! I can't see these modern electric cars becoming survivors like our Triumphs because the technology will become outdated so quickly....but what do I know, I invested in Northern Rock!!! 

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both my moderns also have stop/start and I switch it off every time, I did find out that you can permanently disable it by bridging the "bonnet open" sensor as it needs this to be closed to work, but I have not done it as its just as easy to switch off.  the only other thing the car does is to switch off the radio every ten minutes when iam sitting in the car to save the battery for the stop start, this is a pain, but I live with it.

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On 15/01/2019 at 13:52, Ian Faulds said:

both my moderns also have stop/start and I switch it off every time,

As I keep saying, I both hate it and have it permanently set to default to off on my BMW. Cost me about £100 for the dongle and software. Worth every penny!

If I go into ECO mode it does revert to stop/start - but I don't go into that mode very often - experience has shown that that mode saves about 1mpg on a good day - driving style being more influential. Though saying to lift off when approaching a junction or island etc it mildly amusing. 😂

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