Another Stop/Start Fiasco

[DuncanDisorderly]

Arrgh, I've read hundreds of Stop/Start threads here, and on the VW and Seat forums, very few have any resolve to the 'High Power Consumption'. 

 

My nightmare:

Car (2015 2.0 CRMB Scout) bought from auction, had been sat for 3 months, totally flat. It had a non-original 096 AGM battery fitted. I charged it with a smart charger, it seemed OK, everything except the stop/start worked. High Power Consumption listed as the only reason for the SS not working.

Sat with engine off but ignition and radio on, I got the 'battery low, start engine' message after about 5mins.

I replaced that battery with a new Varta 096 AGM, and had it coded. 

Stop/Start still not working, still have high power consumption message and battery low message after about 5mins.

 

Took it to a local VAG specialist, who condemned the (new) battery. 

Reluctantly replaced the battery again, sent the condemned one back to the supplier, who got on touch to say they'd tested it and it was fine. 

So now I'm on the third battery. But still no SS, and same messages. 

 

Took to an auto-electrics specialist, told them the history. They tested the new battery and confirmed it was fine, said they found an exposed section of wiring from the alternator, that the alternator was partially charging to a 'default' level, but not dynamically as demanded by the car. Wiring repaired, battery charged, tested and re-coded, car ran for a few weeks. Alternator tested and found to be fine. 

Stop/Start still not working, 'high power consumption' still listed in the reason for SS not working. 

 

Replaced the alternator clutched pulley, no reason to but clutching at straws. 

 

Got hold of VCDS, and checked the stop_start_reference_voltage in module 19 CAN gateway, after reading here of the methods to DIS-able stop/start, found that it was bot active and the correct factory reference voltage of 7.6volts. So doesn't appear to have been fiddled with. 

 

Started checking battery charging voltages on the fly, and found that whilst driving, the battery is consistently 12.4v, and the alternator 13.4v whilst driving steadily, EXCEPT on the overrun. Back off the throttle and the alternator voltage shoots to 14.9v with the battery trailing consistently one volt behind at 13.9v. 

 

For reference, this car does very little stop/start driving in towns, its mostly motorway miles with the occasional 10 to 20 mile run. And doesn't spend long periods laid up. I'm not even bothered about the stop/start not working, it's the 'battery low, charge by driving / radio will switch off' messages that are annoying me. 

 

So my big question to the experts is:

 -  Why does the alternator only charge on overrun, 

 - Why do I always have the 'high power consumption' message, when everything OE is switched off and everything aftermarket is physically disconnected and, 

 - Why does the car always think the battery is flat, when it isn't? 

 

Screenshots of normal driving (this was on the motorway, after about 80 miles. First cruising along. Second I'd just backed off the throttle, on the overrun. I've switched the engine off and restarted several times, lowest cranking voltage I can get is 9.7v

 

 

Edited 18 January, 2023 by DuncanDisorderly

[Ootohere]

No idea sorry as electricity is a mystery to me, all magic.

 

But someone will be along hopefully that knows their stuff, and hopefully can help on battery charging when driving.

 

As to Stop / Start, that can be a separate issue, as in, Someone did a good job of disabling Stop / Start.

People have been posting for years asking how to and and getting the answer on how to or what little bit to buy so that it is off and stays off.

Edited 18 January, 2023 by toot

[DuncanDisorderly]

Thanks Toot, I'm a time served mechanic but haven't worked on cars for years, my experience with car charging systems consists of drop tester, amp clamp and multi-meter, alternator should chuck out 13.5-14.5v. These days it seems it's all maps and scopes, and alternators put out anything from 12 - 15v, depending on what they feel like 😂

 

I've read about the button inverters, that turn the 'switch stop/start off' button into a 'switch stop/start on' button. Only thing I can say is, the button itself appears to be OE and it displays as switched off when the button is pressed, at the next ignition cycle the SS is back on again (albeit not working). span widget

Edited 18 January, 2023 by DuncanDisorderly

[nta16]

Please note - I am not a mechanic or expert in anything.

 

I'd give that VAG specialist a very wide berth if they condemned a new battery, new faulty batteries are very rare unless they have been very badly stored neglected and abused and even then you'd probably be able to fully recharge the battery with an appropriate battery charger and have it working well in the short term.  As a a time served mechanic you know what utter boll**cks and with what contempt some in the motor trade give and treat their customers.

 

You could check that the new battery has been coded in correctly to "Fleece", Ah entered correctly and a digit change to the battery serial number at least.

 

If you are sure the new battery is coded correctly as you have a machine that gives those lovely graphics you could try disconnecting the start/stop at the battery and see if things improve, some drive for years with it disconnected at the battery and it done no harm when I tried.

 

I have no proof but I would not have any device plugged into the diagnostics port all the time or for too long, and are you sure it's a VCDS that gives those graphic as the ones posted up here that I see are horrible 1990s style computer screen look, seen Torque screen shots posted here that look more like that.

 

To physically disconnect with hand and fingers the start/stop on my wife's 2015 Fabia you just disconnect the wotsit off the battery negative connector, photos below (not from my wife's car so ignore any other minor issues).  ETA: obviously you'll want to secure the start/stop connector and its lead and protect male and female ends from dirt and debris.

 

If you want to learn about the battery/alternator charging with (and without) start/stop you can plough through the information from here. - https://procarmanuals.com/ssp/

 

 

Edited 18 January, 2023 by nta16
ETA:

[DuncanDisorderly]

Thanks, I knew the new battery wasn't knackered, but that's the route they took with the diagnosis, and they were the experts. 

 

The new battery was coded in with VCDS, the screenshots are from the torque app. I don't leave it plugged in permanently was just looking to see what the voltages are on the fly. 

 

Thanks for those pics, trouble is unlike the majority of posts on here, I want my stop/start to work, rather than disabled. Actually, I just want to get to the bottom of the problem. 

Edited 18 January, 2023 by DuncanDisorderly

[nta16]

Please note - I am not a mechanic or expert in anything.

 

Just in case of 'others' please note my (second) ETA: of - ETA: obviously you'll want to secure the start/stop connector and its lead and protect male and female ends from dirt and debris. - and that I often use incorrect terminology.

 

[Warrior193]

For micro-hybrids like these, it is normal for the alternator to ramp-up charge voltage during overrun or braking (energy recuperation). Considering it appears that you are not doing particularly short trips, it is odd that your battery is not staying at least 60-70% charged. Have you checked for parasitic battery drain while car is shut down?

[DuncanDisorderly]

13 minutes ago, Warrior193 said:

For micro-hybrids like these, it is normal for the alternator to ramp-up charge voltage during overrun or braking (energy recuperation). Considering it appears that you are not doing particularly short trips, it is odd that your battery is not staying at least 60-70% charged. Have you checked for parasitic battery drain while car is shut down?

Only with my good old-fashioned amp clamp. No draw when the car is switched off and properly shut down (takes a while for all the modules to power down I guess). 

[nta16]

Please note - I am not a mechanic or expert in anything.

 

2 minutes ago, DuncanDisorderly said:

Thanks for those pics, trouble is unlike the majority of posts on here, I want my stop/start to work, rather than disabled. Actually, I just want to get to the bottom of the problem. 

I meant the idea of temporarily disconnecting to see if there are differences to help with diagnosis.  I reconnected it on my wife's car and just turn it off (deactivate) at the button when wanted.

 

 

[Warrior193]

1 minute ago, DuncanDisorderly said:

Only with my good old-fashioned amp clamp. No draw when the car is switched off and properly shut down (takes a while for all the modules to power down I guess). 

You will need a reasonably accurate DMM and will have to fool the vehicles various systems into going to sleep - this may require overriding the bonnet open switch, then, with one battery lead disconnected,  measure the current draw between lead and battery terminal. IIRC, quiescent current draw should be only 10-15 milliamps. A search on the forum will probably explain test procedure better.

[DuncanDisorderly]

12 minutes ago, nta16 said:

Please note - I am not a mechanic or expert in anything.

 

I meant the idea of temporarily disconnecting to see if there are differences to help with diagnosis.  I reconnected it on my wife's car and just turn it off (deactivate) at the button when wanted.

 

 

Ahh I see, on these Octys it seems it's a chew on getting it to stop working when it's not wanted, hence the various workarounds. Not as straight forward as disconnecting a wire. 

 

Just another thought, I get that new alternators are effectively smart chargers, does the fact the charge rate drops right down whilst driving not suggest the battery is properly charged? More to the point the car knows it's charged? 

[DuncanDisorderly]

13 minutes ago, Warrior193 said:

You will need a reasonably accurate DMM and will have to fool the vehicles various systems into going to sleep - this may require overriding the bonnet open switch, then, with one battery lead disconnected,  measure the current draw between lead and battery terminal. IIRC, quiescent current draw should be only 10-15 milliamps. A search on the forum will probably explain test procedure better.

Aye, I've got a Fluke multimeter and DC amp clamp, nothing showed on the amp clamp, so measured across the battery negative, very little draw (there was some draw, bu the type that'd take months to drain a battery). 

[ords]

Does the convenience consumers display show anything drawing power?

[DuncanDisorderly]

28 minutes ago, ords said:

Does the convenience consumers display show anything drawing power?

Nothing, everything turned off. I used to leave the mirror heaters on, but not any more. 

Same 'High Power Consumption' message with all the consumers turned off. And dashcam (hardwired to a spare switched fuse slot behind the glove box, I've checked this is powering off with the ignition off) and phone charger disconnected. 

[nta16]

Please note - I am not a mechanic or expert in anything.

 

To me, it doesn't matter as much what is actually happening as what the VW computer programs believe is happening.  I'm all for rebooting the computers and their programs, as far across a yard or field as I can.  😄  I know no more than basics and the fact that computer engineers actually often do resort to resets or "turn off 'n' on agen" so using perhaps VCDS and/or (I favour) quick, free, easy disconnect battery, turn ignition on press and hold brake pedal and turn headlights on, turn all off reconnect battery - but I don't know how that goes on hybrids.

 

Then if you've checked for the (admitted) service recalls and program updates and TSB then wouldn't it likely be wiring, connections, communication fault(s) or unadmitted service recalls and program updates and TSB.

 

I'm annoyed about this on your behalf now. 🤣

 

Good luck.

 

[varooom]

As you probably know, it can take 15-20 minutes for the CANbus to properly go into low power mode, if you have fooled the car into thinking the car is locked, with the bonnet open, then you should know if you have a parasitic draw.  You can do the same with car door open if you fool it also, and check mA across each fuse.

 

Assuming that's fine, then our most like suspect is alternator is being a swine because it's shot, or it's not being commanded to operate when it should be charging.

 

 

The radio shutting down while driving and various similar messages of too much power being drawn when driving also points to the Alternator not being commanded to work (which is odd!) or the Alternator is buggered.  That message shows up when you're taking more from battery than your putting in (once the battery Voltage drops to unsafe values)

[Warrior193]

54 minutes ago, DuncanDisorderly said:

Nothing, everything turned off. I used to leave the mirror heaters on, but not any more. 

Same 'High Power Consumption' message with all the consumers turned off. And dashcam (hardwired to a spare switched fuse slot behind the glove box, I've checked this is powering off with the ignition off) and phone charger disconnected. 

Hi Duncan, just be aware that the message 'High Power Consumption' can mean a number of things - often it simply means that battery SOC is too low at the time. One reason can be due to short runtime since start. 

[Warrior193]

1 hour ago, DuncanDisorderly said:

Ahh I see, on these Octys it seems it's a chew on getting it to stop working when it's not wanted, hence the various workarounds. Not as straight forward as disconnecting a wire. 

 

Just another thought, I get that new alternators are effectively smart chargers, does the fact the charge rate drops right down whilst driving not suggest the battery is properly charged? More to the point the car knows it's charged? 

The 'smart charging' system will usually only allow the alternator to keep the battery charged to approx. 70% max - so as to allow available capacity in the battery under energy recuperation conditions.  

[Ecomatt]

There is a good chance the last owner might have done some coding in that control unit. I would speak to someone who has access to odis and reflash the original coding. Odis would also do diagnostic checks and find out what the issue is. Without it it can be like shooting in the dark with these types of faults.

[DuncanDisorderly]

18 hours ago, varooom said:

As you probably know, it can take 15-20 minutes for the CANbus to properly go into low power mode, if you have fooled the car into thinking the car is locked, with the bonnet open, then you should know if you have a parasitic draw.  You can do the same with car door open if you fool it also, and check mA across each fuse.

 

Assuming that's fine, then our most like suspect is alternator is being a swine because it's shot, or it's not being commanded to operate when it should be charging.

 

 

The radio shutting down while driving and various similar messages of too much power being drawn when driving also points to the Alternator not being commanded to work (which is odd!) or the Alternator is buggered.  That message shows up when you're taking more from battery than your putting in (once the battery Voltage drops to unsafe values)

Hi, the radio doesn't switch off whilst driving, after about 5 mins of the engine being off but the ignition on, I get the '12v low, charge by driving' and 'Infotainment will switch off' messages, suggesting the battery is flat. 

 

I'd frigged the bonnet switch to get everything to shut down, took about 10mins IIRC. 

 

Failing alternator makes sense. I've had it tested though and it couldn't be faulted, and I like to prove faults before replacing parts, otherwise things get very expensive very fast! 

 

Have checked the stop-start modules with VCDS, it has the correct reference voltage (7.6v)  stored, and is activated. I only checked this after reading methods on here to disable the system. 

[DuncanDisorderly]

18 hours ago, Warrior193 said:

Hi Duncan, just be aware that the message 'High Power Consumption' can mean a number of things - often it simply means that battery SOC is too low at the time. One reason can be due to short runtime since start. 

I understand that mate, bit frustrating when it's ALWAYS showing, under all driving conditions. 5 mins after startup is fair enough, but 3 hours into a 5 hour motorway run it shouldn't be there. 

[varooom]

Yes alternators are not cheap, do you have access to VCDS full time, or was it just plugged in and you see the logs?

Ideally a full VCDS scan of the car would be a good thing to post if you have it, though as you well know, no faults codes doesn't stored always mean a thing.

 

EDIT:

p.s. I was hoping to take laptop out to the car today and do a log of the Voltages during driving.  It has sat for a whole week, so should need a good top up!

If I can, I will post up a log later on of live data logging that might be a good comparison to your own (if you have easy access to VCDS)

Edited 19 January, 2023 by varooom
Additional Information

[DuncanDisorderly]

The battery monitor on the negative battery terminal, is there a way to reset this?  As in, can I clear its memory (if it has one), reset everything and charge the battery off the car? Reconnect and recode the battery and and let it relearn the parameters?

[varooom]

7 minutes ago, DuncanDisorderly said:

The battery monitor on the negative battery terminal, is there a way to reset this?  As in, can I clear its memory (if it has one), reset everything and charge the battery off the car? Reconnect and recode the battery and and let it relearn the parameters?

It transmits battery temperature and Voltage I believe onto Gateway, and the only "reset" as such is to tell the Gateway you have installed a "new" battery so it can relearn charging.

 

Take a look at this, I think it tells you https://procarmanuals.com/pdf-online-vag-ssp-504-vehicle-batteries/  about the monitor (need to check myself again)

 

EDIT:

Try this one about Stop/Start, you will see information about the monitor and where it sends data via LINbus

https://procarmanuals.com/pdf-online-vag-ssp-426-start-stop-system-2009/

Edited 19 January, 2023 by varooom
Additional Information

[varooom]

Only basic, but did some quick and dirty data logging.

 

RPM over initial 30s cold startup (slightly lower Voltage as I was setting up with engine off of course - was 12.3V on meter)

 

 

Battery Voltage over the first 30s after cold start (the lower Voltage when cranking was to be expected as it took time to setup datalogging, the droop at 15s was heated screen going on)

I recorded about 3 minutes of data, that was over 14 Volts, as the heated screens were on, and the Voltage didn't drop lower than this.