Stop/start,,,, battery voltage level controlled ?

[Jinnek444]

HI all,
here'a thing I've been meaning to ask about for donkeys.
On the original battery, car (quattro Avant 2ltr) new early 2018 till mid 2021, the stop/start barely ever worked, if I charged the battery it would sometimes work. As well as getting spurious warnings, door child locks US, can't remember the others now.
After being fobbed off by Stirling Audi, in fact I think it must have cost more to kick the problem down the road, with me being in and out, loan car, "master mechanics" ho ho time, than address it, because the car was still in warranty, I then put a new battery in myself.
Stop/start worked for a time, then did'nt. Then, last Thursday, taking my wife into town, it suddenly started working, and at every set of lights. And it's now been working intermittently since. Longer days, less darkness ?
So, my question, eventually, is the stop/start operation governed/allowed by the battery voltage, I think it might be. And if so, is it possible to lower the setpoint voltage below which it becomes inoperative, so that it is more reliable, predictable.
Cheers.

 

[Gazwould]

Do you think Stop Strain is a good thing ?

 

[Daggerit]

There are tons of things which affect it.

I found something as simple as having the climate control not synced up could stop it working completely. Same goes for cold engine, low batter voltage, heated seats, A/C, etc. Lots of reasons it doesn’t work.


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[Jinnek444]

Hi Daggerit,
I appreciate that, but in this case, no settings have been changed over the years. I think your are right on the cold engine point though.
A/C stays at what it is, never use heated seats, climate control, no idea. etc.
Which is why I suggested voltage level. I was out today, and it was active at traffic stops.
Would, is, it possible to lower the threshhold it operates above. I have no knowledge of coding to start with. Indeed, is there such a setting somewhere to change. Dunno. I did code in the new battery, but that's my limit, I would think.
Gazwould. Is it a good thing. Some of the lights sequences at junctions we have around here, if you just miss the green, it can be 5 minutes before the next change. In fact, sometimes I turn the thing off manually.

 

[Daggerit]

Hi Daggerit,
I appreciate that, but in this case, no settings have been changed over the years. I think your are right on the cold engine point though.
A/C stays at what it is, never use heated seats, climate control, no idea. etc.
Which is why I suggested voltage level. I was out today, and it was active at traffic stops.
Would, is, it possible to lower the threshhold it operates above. I have no knowledge of coding to start with. Indeed, is there such a setting somewhere to change. Dunno. I did code in the new battery, but that's my limit, I would think.
Gazwould. Is it a good thing. Some of the lights sequences at junctions we have around here, if you just miss the green, it can be 5 minutes before the next change. In fact, sometimes I turn the thing off manually.

I really don’t know if that’s possible or not to g be e honest. As long as it doesn’t drain the battery by accident then you should be good.


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[Gazwould]

Stop Strain...

It will save very little fuel but will cost you much more in increased maintenance through component wear depending on car spec like starter motor , alternator , ring gear , battery , auxiliary battery / capacitor , alternator and drive chain tensioner etc .

Most common is the early replacement of batteries that would otherwise still start the car for years to come , this is not 'Eco' .

And very often not the fix to a sensitive too many prerequisites abomination con device .

 

[Daggerit]

Stop Strain...

It will save very little fuel but will cost you much more in increased maintenance through component wear depending on car spec like starter motor , alternator , ring gear , battery , auxiliary battery / capacitor , alternator and drive chain tensioner etc .

Most common is the early replacement of batteries that would otherwise still start the car for years to come , this is not 'Eco' .

And very often not the fix to a sensitive too many prerequisites abomination con device .

I get your point but if everything has been designed for that purpose then I imagine there should be no additional maintenance required. How many batteries have you replaced with a stop start car? I can’t say I’ve heard of an underlying problem in that regard, but I’ve also not specifically searched for it.

In terms of saving you fuel, it definitely helps. I tried driving the same route with and without it activated for week long intervals over the same commuting route and there was about a 5mpg difference. Depending on your tank size that could be 50+ miles more between fill ups. That’s just my experience though, and will change based on the car and engine type I’d imagine.


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[Gazwould]

Exactly , earlier cars , SS was just a bolt on idea with no extra robustness to components of which we can add engine mounts to the list.

The replacement of batteries is a guess on the owners part , sometimes with success but that battery will still start the car for years to come.

Hybrids are much better though .

 

[cuke2u]

I get your point but if everything has been designed for that purpose then I imagine there should be no additional maintenance required. How many batteries have you replaced with a stop start car? I can’t say I’ve heard of an underlying problem in that regard, but I’ve also not specifically searched for it.

In terms of saving you fuel, it definitely helps. I tried driving the same route with and without it activated for week long intervals over the same commuting route and there was about a 5mpg difference. Depending on your tank size that could be 50+ miles more between fill ups. That’s just my experience though, and will change based on the car and engine type I’d imagine.


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You are correct, everything is designed around the stop start systems, from the starter motor to the alternator to the engine oil. The engine is also stopped at a particular cycle of the pistons to ensure less wear and tear.

Stop-start engines and engine idling – the law and common myths revealed | RAC Drive

Does it use more fuel? Does it cause more pollution? We decided to unearth the facts and find conclusive answers.

www.rac.co.uk

Myth-busting: Does stop-start damage your engine? | Practical Motoring

Plenty of people will tell you what they like and don’t like about stop-start systems. But, does stop-start damage your engine?

practicalmotoring.com.au

Unfortunately though there are still plenty of opinionated individuals still perpetuating myths who don't really understand how it works..

 

[Gazwould]

Love these articles written under the influence , often see 'white papers' with massive flaws .

Always best to read the comments of people and have an ear to the ground what actually happens in the real world .

Are 225 width tyres actually 225mm , quite often not !

 

[Booboo]

I have a 2018 A4 mild hybrid & I've had to have a new battery already.
SS kills batteries

 

[Daggerit]

I have a 2018 A4 mild hybrid & I've had to have a new battery already.
SS kills batteries

Was it actually the SS that killed it though? My 2022 motorcycle has gone through a battery already and doesn’t have stop start, sometimes it’s just a bad battery.


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[Gazwould]

That's certainly a faulty battery to go within a few months , 4 years is questionable .

Are Audi OEM still Varta ?

The old OEM Varta could last 12/13 years.

 

[Garrett 69]

Batteries are built to fail these days, just like anything else. 12+ yr old batteries aren't a good business model for the battery manufacturers.

 

[Jinnek444]

The battery in my A4 from new was not up to standard (for the vehicle). No, well once only, stop/start, warnings of various , spurious, imagined faults. But as was said above .
Without all the electronics fault checking and S/S, I would not have been the wiser. And probably still on the original unit.

 

[Booboo]

That's certainly a faulty battery to go within a few months , 4 years is questionable .

Are Audi OEM still Varta ?

The old OEM Varta could last 12/13 years.

Yes they are

 

[DyslexicDog]

Other impacts of stop/start to include are side loading to the rear main bearing, caused by lack of lubrication during a crank event. You've also got the piston rings and the lubrication impacts of not keeping a constant oil film.

I'm sure the manufactures have worked out lots of the kinks and increased the durability and longevity of the components, but it's a no from me. I keep start/stop switched off.

 

[Jinnek444]

An update on this old thread.
Couple of weeks ago,just by chance, as I was approaching my house, I turned the air-con off, no idea why, it is has always been on the eco setting.
Stopped to wait for the gates to open, and the engine died. Then I twigged the s/s had worked. Why.
Well, on trying to reproduce it, I found that with air-con Off, the s/s can hardly restrain itself. Stop for a couple of seconds, off.
Air-con set to eco or up, nothing, dead, no chance. nothing to see here.
BTW, I phoned Audi helpline a couple of months ago, got a guy in India, he took the story, and unbeknown to me passed it on. I got a call a couple of days later, a tech from Perth Audi, repeated the story, his reply verbatim, "these cars have a mind of their own". Oh to be a technician.
I've now sent an email to Audi UK, we'll see what transpires there.
Regards.

 

[Booboo]

Could have been turned off via carista? This tricks the car in believing the aircon system is draging loads of power this disables the S/S. If the Aircon is turned off the S/S will work like default

 

[Jinnek444]

Hi Booboo.
No, I've had the car since new. It's been like this from the start.
I think it worked once shortly after I got it. I was coming down a slight grade, trailing throttle to some lights, and I noticed the engine had died.
Picked away again as the lights turned.
Got a reply from Audi asking for reg. no. and phone number. Says they have to diagnose it. Well, Stirling Audi did that to no effect. In fact, I was coming back on the expressway, and it sort of died, at 60ish, or went to idle, no reponse to the throttle, for quite a few seconds, I really thought I was going to be stranded in the middle lane with a dead car.
It came back on, I got off at the next slip, and phoned them, but Sat afternoon, just, and no mech staff on. I looked at the dash-cam later, but for some reason it had missed the expressway swearing, and only had the phone call to them.
I'll reply to them, but no high expectations.