I got a mk4 and S/S works intermittently however I personally don't like the system and wish it was disabled permanently.

I like yourself have a dashcam hardwired with parking mode but it's been running sweet over the last two months. 

However I will also be getting a voltage meter to keep a close eye on matters 

So yesterday I drove to Corsham and back, 2.5 hours each way, 170-odd miles.

My SS STILL doesn't work due to "vehicle charging".

On a 6 month old Mk4 Focus.

That's a bit rubbish frankly.

I've found that in similar situations , it works the following day! I can only guess that it takes the BMS system some time with no load, to assess the battery charge state

I think you're right. It did work today.

On 2/28/2020 at 6:34 AM, ianincheshire said:

I've found that in similar situations , it works the following day! I can only guess that it takes the BMS system some time with no load, to assess the battery charge state

 

13 hours ago, Guy Heaton said:

I think you're right. It did work today.

Apologies for contradicting you guys but I have done a lot of live data logging on my car and the Battery State of Charge percentage goes up as the car is being driven and I have not noticed it jump up any more the next morning.

In your situations it is likely that S/S was disabled because  the battery was deemed too hot for S/S to operate in the interests of engine longevity. This does not mean that it was overheating, it is one of the many features that are for our benefit and shows a great deal of diligence on the part of the Engineers given the constraints put on them by the Green legislation even though it seems to get on a lot of peoples nerves.

For information there are a lot of technical reasons as to why S/S has been disabled (the number is a fairly high double figure although I have not actually counted them), this does not necessarily mean that there is an actual fault with the car although there could be.

I'll probably get trolled for this post, but it is based on my own findings and Engineering background.

The battery monitoring system does reset when the car is parked up and locked for more than 8 hours. This can cause the state of charge value to go up or down. Of course, if the state of charge value calculated during the journey was already correct it won't change. I have seen mine go down by up to 10% or up by up to 12% overnight but usually it is within 1% in the morning of where it finished when I switched it off the night before. I have been monitoring it daily for the last couple of months. The biggest overnight changes usually occur after very short journeys or very long ones. My normal commute is 15 miles each way and the state of charge doesn't change much overnight after these journeys.

My stop start doesn't work because the state of charge has never got over 60% in the last 2 months, probably because my battery is 7 years old.

Well guys,

MY Focus is 2008 ST so don`t have these issues with stop/start, I do though own a 2012 Merc coupe and a 2014 Porsche cayman 981,

Stop start is my pet hate and have disabled the system on both the Porsche and Merc. Regarding the Porsche and the Merc a simple way to get rid of this system is to disconnect the battery sensor attached to the negative clamp of the starter battery (BMS), this also gets rid of smart charging which is the cause of your under charged battery, the BMS is of little actual value but does cause the battery to become partially charged for long periods especially on short runs which shortens it`s life, manufactures say smart charging saves fuel, the savings are minimal in real life.

If you check the voltage when driving the car with BMS in play you will note the voltage fluctuates between the low 13 and high 15 volts, 13 volts is providing vertically no charge so the longer you see 13 volts the less the battery is being charged.

With the sensor out of play the ECU which controls the alternator can`t read the SOC of the battery and instructs the alternator to enter a continuous charging regime of around 14.2/4 volts at this charge voltage the battery will get fully charged even on short journeys and the battery will obviously last longer. 

Stop/start will shorten the battery's life by about half, the merc`s battery is dated 3811, that`s over 8 years old and it still shows 12.8 volts.

Plug voltage meter into cig socket as shown in my vid below.

 

5 hours ago, robuk2 said:

Well guys,

MY Focus is 2008 ST so don`t have these issues with stop/start, I do though own a 2012 Merc coupe and a 2014 Porsche cayman 981,

Stop start is my pet hate and have disabled the system on both the Porsche and Merc. Regarding the Porsche and the Merc a simple way to get rid of this system is to disconnect the battery sensor attached to the negative clamp of the starter battery (BMS), this also gets rid of smart charging which is the cause of your under charged battery, the BMS is of little actual value but does cause the battery to become partially charged for long periods especially on short runs which shortens it`s life, manufactures say smart charging saves fuel, the savings are minimal in real life.

If you check the voltage when driving the car with BMS in play you will note the voltage fluctuates between the low 13 and high 15 volts, 13 volts is providing vertically no charge so the longer you see 13 volts the less the battery is being charged.

With the sensor out of play the ECU which controls the alternator can`t read the SOC of the battery and instructs the alternator to enter a continuous charging regime of around 14.2/4 volts at this charge voltage the battery will get fully charged even on short journeys and the battery will obviously last longer. 

Stop/start will shorten the battery's life by about half, the merc`s battery is dated 3811, that`s over 8 years old and it still shows 12.8 volts.

Plug voltage meter into cig socket as shown in my vid below.

 

This was traditionally the way to disable Smart Charging, but on some cars the Charging Light would stay permanently on if you did this, although not on your Merc or Porsche though. I don't know what it does with modern Fords.

Given that most people posting to this thread have a MK4 Focus it would be prudent to be cautious in case it has a knock on effect on something else and there could be warranty problems.

From my own observations when these cars are first started they charge conventionally for a time and then revert to one of the two Regeneration or the Refresh modes. This is when the Voltage drops to 13V and the Current can be as low as a pulsed 0-1 Amp. This is not good for charging speed but is good for other reasons. It may be that given the power hungry demands of a more modern car that this regime will result in the battery lasting longer than only traditionally charging it. 

Quote

It may be that given the power hungry demands of a more modern car that this regime will result in the battery lasting longer than only traditionally charging it. 

The Mer`c battery as shown is over 8 years old, the Merc is a Blueefficiency petrol auto with installed command sat nav, when battery`s were last checked about a month ago the voltage showed 12.7-.8 on both after overnight standing, the car is parked outside and starts instantly. ( model yrs 2012-2015 ). If later cars are actually more power hungry a larger alternator and battery would obviously have been fitted to cope. There is a large amount of misinformation placed on the net and forums relating to this subject. If smart charging were not a problem why so many complaints relating to failed or undercharged battery`s in cars with stop/start.

Smart charging is the reason stop/start is intermittent, unfortunately for some both systems use the same sensor.

I disliked stop/start to such an extent I decided to test this disconnect on the Merc, if there were any problems associated with this simple method it would have already reared it`s head well before now. 

Agm batterys are advertised as stop/start battery's, nothing to do with any other systems fitted to the car, if you don`t have stop/start you don`t need an AGM or an EFB.

2010 Mercedes 1.6 C180 BlueEFFICIENCY Kompressor Sport 4dr Auto  (no stop/start.   https://www.motors.co.uk/car-55902267/?i=2&m=sp       Lion 027 Car Battery - 3 Year Guarantee    Note the reg on Merc and reg on euro parts.

Quote

However, vehicles with start-stop technology place a greater demand on a vehicle’s battery – and this is where the AGM battery stands head and shoulders above the more conventional acid flooded lead battery.

https://www.racshop.co.uk/advice/what-is-an-agm-battery

https://www.rotronicsbms.com/battery-tips/what-you-need-to-know-about-efbs-enhanced-flooded-batteries/

The Porsche 981 was produced from 2013 to 2016, this is a modern car in my view, mine is a £30,000 vehicle which no longer has stop/start and regeneration.

https://www.netcarshow.com/mercedes-benz/2012-c-class/

 

On 7/12/2019 at 9:00 PM, Rattus said:

Sorry, missed one.

Yes the stop/start symbol is greyed out.  I have been all through the menus switching it off, then going for a drive and then switching it back on again. I am pretty sure I have tried every feasible combination of stuff switched on and off to see if there is a difference.

I have just been on Amazon to sort a voltage monitor which will be here tomorrow, so we will see.

Picked my focus up yesterday and stop start wasnt working . So read advice on here.... turn ignition on wait 10 seconds then 5 presses of rear fog light button then 3 of the hazard warning light . The battery light will blink then hey presto mine works fine now

(1) Why do you need stop/start on a 1 litre engine (2) It won`t work for long.😉

17 hours ago, Morty1977 said:

Picked my focus up yesterday and stop start wasnt working . So read advice on here.... turn ignition on wait 10 seconds then 5 presses of rear fog light button then 3 of the hazard warning light . The battery light will blink then hey presto mine works fine now

@Morty1977 Is your car a MK3.5 or a MK4. I'm curious to know because I knew that procedure to reset the BMS worked on earlier Fords but I was not sure if it still worked on the MK 4's.

MK 3.5 67 plate registered as 2018 mate works fine now mine

2 minutes ago, Morty1977 said:

MK 3.5 67 plate registered as 2018 mate works fine now mine

Thanks for confirming that. I have a MK 4 and have not had any Battery problems and I can do a BMS reset with FORScan, but was wondering if anything had changed for the newer model cars.

No probs mate only got mine monday useful is this site 🙂

7 hours ago, robuk2 said:

(1) Why do you need stop/start on a 1 litre engine (2) It won`t work for long.😉

Now now 😉

Well, have been away from here for ages but, the car had its second service this week at 22,500 miles (14 months old).

Once again the instructions to the dealer were to investigate stop/start as it has not worked since last service. Hey presto! They found an error in the telematics communications. New software installed,  eventually as it all crashed!!

The result is, a functioning stop/start! Only took a year to sort out, but all is good.

Can only thank everyone for their input and comments. Pity we are about to go into lockdown or else some good runs out could be done!!!

Keep safe everyone.