Mk7 Stop/Start System - Issues and Questions

[Regbaon]

For the last two days I have been unable to get this function to work. Usually it defaults to being on unless you turn it off. I have turned the switch on and off several times, driven with A/C on and off. I have driven the car often enougn to know I have a problem.*I know some of you hate this function but i'm a fan of it. Anyone else had problems with this feature?

I note you live in Adelaide a pretty hot State in summer,so I think the warning on page 212 in the manual about damage to the battery when outside temps are high should be noted,that's why I decided to turn mine off.

[Moonee]

Had an interesting one the other day. Car had stopped with auto stop/start when all of a sudden it started up on its own. It was a cool day so the aircon was not running.


Speaking of aircon, is the aircon in the MK7 electric or at least capable of running independent of the engine? This is the first car I've owned where the aircon continues to run fine even with the engine off.

[Kesh]

Had an interesting one the other day. Car had stopped with auto stop/start when all of a sudden it started up on its own. It was a cool day so the aircon was not running.


Speaking of aircon, is the aircon in the MK7 electric or at least capable of running independent of the engine? This is the first car I've owned where the aircon continues to run fine even with the engine off.

Nah the AC compressor still runs off the engine belts. It'll stay cold for a little bit while it's clearing the pipes, then it'll slowly go back to being fresh air again. If you have it on a really slow fan speed, you might have some cold air in there for the whole duration the engine is off.

[jonoz]

Anyone else's stop-start seem to have become a little sluggish in engaging 1st gear after being stopped?

[lambertia]

Anyone else's stop-start seem to have become a little sluggish in engaging 1st gear after being stopped?

Yes. Sometimes in can take a couple of seconds and some times it engages the clutch resulting in an incredibly violent jolt forward.

[Lemonskin]

Anyone else had this? Popped up on my trip back from the south coast today. Remedied by turning the car off and on again but I hope it's not some underlying problem that will give me grief.


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[DV52]

Anyone else had this? Popped up on my trip back from the south coast today. Remedied by turning the car off and on again but I hope it's not some underlying problem that will give me grief.

Lemonskin: Have you tried touching the area of the screen where the error message is displayed? I just wonder whether in doping so, you would get a better explanation of the fault.

[kevcol]

I presume most users turn their stop start system off at night due to the added load of the lights on the battery.
I also guess the batteries used are similar to "deep cycle" batteries used with solar panels that can be discharged deeper and more often than standard batteries which can tolerate only shallow cycles.
As an aside I wondered what VW regenerative braking was until I read it had nothing to do with the brakes but was just control of the alternator so it does not charge when accelerating.
The world desperately needs a replacement for lead acid battery technology.

[Eaglehawk]

I presume most users turn their stop start system off at night due to the added load of the lights on the battery.

A Despicable Me minion's "Whaaaahh?"

[DV52]

I presume most users turn their stop start system off at night due to the added load of the lights on the battery.
I also guess the batteries used are similar to "deep cycle" batteries used with solar panels that can be discharged deeper and more often than standard batteries which can tolerate only shallow cycles.
As an aside I wondered what VW regenerative braking was until I read it had nothing to do with the brakes but was just control of the alternator so it does not charge when accelerating.
The world desperately needs a replacement for lead acid attery technology.

keycol: The mk 7 uses what's called an EFB, (Enhanced Flooded Battery) which is a little different to the normal wet-cell batteries in cars (these days, these are mostly AGM, - Absorbent Gas Mat batteries) . If you pull-up the battery "cossie" and you look at the top of the battery, you should see the word "EFB" on the battery, (see pic)

EFBs are more suited to stop/start cars because they have better "Cycle Resistance" and they have better "Layer Resistance"

On a EFB the positive plate inside the battery is coated with an extra polyester fabric. According to VW's literature, "this gives the active battery mass additional grip on the plate". This increases "Cycle Resistance" which is the number of cycles of charge/discharge before the performance of the battery is compromised. In this way, the EFB is more compatible with Stop/Start because of the continuous cranking cycles.

The other feature of EFB is the use of passive mixing elements in the battery which allows a better electrolyte circulation. What this does is to better combat what's called "Battery Layer Resistance" which happens when the battery experiences severe discharge (this causes unequal acid concentrations to occur at different parts of the battery which results in the electrolyte being deposited on the plates - causing lowered battery performance.)

So, whilst I understand your concern about the additional load on the battery at night (this would normally be managed by the Battery/Alternator working together), I'm not sure that you actually need to switch-off S/S.

My view is that there are much better reasons to switch off S/S ALL THE TIME. I reckon that S/S is the most dangerous thing in the car. I disabled it long ago (VCDS tweak)