Stopping 'stop/start'

[st13phil]

Frankly, this is all a waste of time.

All the AMG cars with stop/start default to Comfort mode for the gearbox on startup. As soon as you select Sport, Sport+ or Manual mode for the 'box, stop/start is disabled.

 

[Gazwould]

Here's another option: buy and fit a failed auxiliary battery from Terry or Olly... and hey presto no more Stop/Start

You can add me to that list MJ , any drawbacks of a failed auxiliary ?

Where is it located ?

 

[markjay]

....any drawbacks of a failed auxiliary ?...

No idea. I suspect not, based on various posts.

...Where is it located ?

It varies. On my W204 facelift, it's in the spare wheel well in the boot, under a black plastic cowling.

 

[markjay]

Or you can try simply disconnecting the auxiliary battery, and see if there are any lights or warnings on the dash....

 

[markjay]

No idea. I suspect not, based on various posts.

E.g.:

auxiliary battery what is if for?

 

[Bobclive2]

Or you can try simply disconnecting the auxiliary battery, and see if there are any lights or warnings on the dash...

Just disconnect the negative rail battery sensor on the main battery, 5 minute job, hardest part is taking battery cover off, you will loose brake hold but nothing else, stop/start will be deactivated.
The battery will charge within safe limits below 14.4 volts no matter how you load car electrically, in fact the battery will now get a full charge instead of an 80% charge if sensor is connected, there are no warning or engine check lights and the car drives as normal. My car is a 2012 c-class coupe AMG style petrol 1.8 cgi auto. Without stop/start the expensive battery is not needed as it is only necessary if stop/start is active. You will read on the net that if you replace a AGM battery with an normal lead acid it will not last long, that is only valid if stop/start is activated and the sensor is in place as the alternator will then be instructed to charge up to 15 volts which will overcharge a normal lead acid battery leading to a short life.

Smart alternators and regenerative braking. - VW T4 Forum - VW T5 Forum

 

[moodi]

Frankly, this is all a waste of time.

All the AMG cars with stop/start default to Comfort mode for the gearbox on startup. As soon as you select Sport, Sport+ or Manual mode for the 'box, stop/start is disabled.

Why a waste of time? Deactivating a feature that you never want on, regardless of selection?

 

[Bobclive2]

Frankly, this is all a waste of time.

We don`t all own AMG cars

Has anyone else tried the neg rail sensor disconnect.

 

[st13phil]

Why a waste of time? Deactivating a feature that you never want on, regardless of selection?

Because it is only active in Comfort mode, and Comfort mode is the default at start up. If you intend to drive the car in any of its more responsive modes you have to select either Sport, Sport+ or Manual anyway, which turns off stop/start. So you either start the car and deselect stop/start, or you start the car and select a different driving mode.

There's an enormous amount of BS spouted about stop/start. It works fine. The car doesn't break because it's operative. On the AMG V8 cars it's absolutely instantaneous in operation when you prod the loud pedal or take your foot off the brake as it doesn't just rely on the starter motor to fire the engine - there's no hesitation. The real benefit is that in stop/start traffic it's the difference between single digit mpg and 20+ mpg. Anyone who wants to watch the fuel gauge head south while they're going nowhere has a perverse take on driving.

Disconnecting the aux battery to defeat stop/start is like like blowing your foot off because your toe nails need cutting. The "cure" is worse than the (non existent) problem.

 

[Yugguy]

That may be true of the very powerful engines but the 1.0 seat auto I had stuttered and juddered when trying start and drive at the same time. But yes, disconnect or breaking a part of the car doesn't seem like a good idea.

 

[Ted]

Just to clarify on the debate.
Vehicles with stop/start don’t charge constantly at 15 volts. The do it on the overrun and then, for a maximum of around 30 seconds.
Then when accelerating, they stop charging, allowing the battery to go to around 13 volts.
Use of an agm (or efb if it is a cheapie) is because they are much better at handling the charge/discharge cycles and deep discharge cycles than a standard lead acid battery.
The sensor on the battery measures state of charge (from voltage) state of health (by measuring current/voltage at startup via a low value resistor built into the sensor). The built in software does the rest.

 

[Bobclive2]

Vehicles with stop/start don’t charge constantly at 15 volts.

It doesn`t matter whether it charges constantly or not, it appears 15 volts kills a standard lead acid battery plus all the stop/starts if stop/start is working.
The only reason for the expensive AGM battery is the stop/start system, nothing else, our Merc`s ran without problems with standard battery's prior to stop/start.

The stop/start system relies on the battery sensor, if that fails the alternator has to revert to a default charge otherwise the car would stop shortly after the failure of the sensor, I believe BMW had a problem with their sensor which stopped the car from starting.

I don`t like stop start, even more so if it is intermittent, I am not bothered about brake hold either, I believe I have found a way of deactivating stop start which appears to be working.

 

[moodi]

Because it is only active in Comfort mode, and Comfort mode is the default at start up. If you intend to drive the car in any of its more responsive modes you have to select either Sport, Sport+ or Manual anyway, which turns off stop/start. So you either start the car and deselect stop/start, or you start the car and select a different driving mode.

There's an enormous amount of BS spouted about stop/start. It works fine. The car doesn't break because it's operative. On the AMG V8 cars it's absolutely instantaneous in operation when you prod the loud pedal or take your foot off the brake as it doesn't just rely on the starter motor to fire the engine - there's no hesitation. The real benefit is that in stop/start traffic it's the difference between single digit mpg and 20+ mpg. Anyone who wants to watch the fuel gauge head south while they're going nowhere has a perverse take on driving.

Disconnecting the aux battery to defeat stop/start is like like blowing your foot off because your toe nails need cutting. The "cure" is worse than the (non existent) problem.

I guess that is your opinion. Some people, myself included, hate with a passion the thought of this feature on such a car in any driving mode. "Almost instantaneous" and the momentary shut off is never good enough for some of us purists.

I would get it coded out rather than disconnect the battery, as some folks have usefully given more information on in this thread.

Good to know there is a sensible workaround.

 

[markjay]

Just to say that on later models the Stop/Start function is activated with the transmission Comfort Mode or Economy Mode, and deactivated with all other modes (e.g. Sport Mode).

BUT on earlier models (my 2013 W204 included) the Stop/Start function is totally independent from the transmission modes.

I.e., the green Eco light comes on when starting the engine, and remains on until I press the button to switch it off.

I can switch the transmission modes from E to S and back and this will have no effect on the green Eco light, and vice versa.

There were suggestions that it might be possible to reprogram the Stop/Start ECU on my W204 to activate with E and deactivate with S, but I never explored this so I am not sure.

 

[ShaunB]

Aye, the missus has it in her manual Fiesta and I don't mind it there as I can control it and do use at lights when stopped for a while.

Surely you can also control it in the Mercedes, light brake pressure will disable the feature, and keep the engine running.
I know I can anyway, so I wouldn't think your car would be the slightest bit different.

 

[Bobclive2]

Just to say that on later models the Stop/Start function is activated with the transmission Comfort Mode or Economy Mode, and deactivated with all other modes (e.g. Sport Mode).

Not on my 2015 SLK, I have been testing the battery sensor disconnect for about 2 weeks on my Jan 2012 c-class coupe cgi, up to the present car runs as normal other than no brake hold, there are no warning lights showing, battery charges within range and does not exceed 14.4 volts. The car starts instantly on an almost 6 years old battery which is now being fully charged, will see how things progress over the coming weeks.

 

[st13phil]

I guess that is your opinion.

Indeed it is. It's actually my informed opinion based on almost 6 years and more than 70k miles of using E63 Biturbo's as a daily driver.

Some people, myself included, hate with a passion the thought of this feature on such a car in any driving mode. "Almost instantaneous" and the momentary shut off is never good enough for some of us purists.

If it makes you happy, crack on

 

[moodi]

Of course it is your car and opinion but I still don't understand why the debate on how to turn the feature off is a waste of time based on your entitled opinion?

Wonderful to hear your stats and that you have no intention of turning it off - but I do and so may others. So, very grateful to everyone else on the board who has given useful and constructive replies. It looks like there are a few ways to achieve this.

Let's crack on lads.

 

[Gazwould]

Start- Stop is bad for the car , just like DPF and EGR .

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Quick one , battery charging via engine bay jumping posts , yes ?

 

[littleowl]

My stop/start isn't even functional a lot of the time - strangely as the last car I had with it it was on pretty much all the time? Is it because the car has so much going on it has to be 'just so' to work