Has anyone solved this issue. I'm on my second focus. Both have had stop start not working. Current 2021 model had from new worked OK for 1st year then packed up. Garage reset it, lasted 2 days. Battery full on trickle charge, no better. Tried various suggestions, ie fog light 5 times hazards 3 or main beam 5 times, brakes 3 but still not reset bms. Not good for environment and Ford should help but don't suppose they will. Booked into main dealers again but expect it will last 2 days again. Surely not a new battery needed at 12,000 miles? Renewing battery not good for environment either! 

Only 1662 threads on the subject. Have a read ......

https://www.fordownersclub.com/search/?q="Stop Start"&quick=1&updated_after=any&sortby=relevancy

Perhaps we need a new thread: my stop/start IS working. Might not get many contributions though. 

It's a hideous feature anyway, why would folk want their car to 'stall' every time they come to a halt. Surely they know it was only invented so that manufacturers can con their way through a false emissions certificate??

1 hour ago, StephenFord said:

It's a hideous feature anyway, why would folk want their car to 'stall' every time they come to a halt. Surely they know it was only invented so that manufacturers can con their way through a false emissions certificate??

It has been proven to reduce fuel usage if you stop for more than about 7s. But the main concern for me is if there is additional wear it causes. I usually leave it to its thing unless I know I’m not going far though and want to let the car warm up and charge the battery. 

42 minutes ago, alexp999 said:

It has been proven to reduce fuel usage if you stop for more than about 7s.

Claims on the fuel savings (if any) are wide and varied suggesting that there is no definitive proof of what savings there are. Very much like those who claim that EV's are 'zero' emissions.

A quick look at some figures on claimed fuel savings are:

• Google (source not divulged) say 15-20%  of fuel, but only in certain conditions.
• RAC, 5-7% improvement in fuel
• AutoCar, Yes (but don't seem to quote a figure)
• Kwik Fit, up to 7% fuel saving
• CarsGuide, 8% saving
• GEM Motoring, Initial fuel savings are likely to be eclipsed by higher maintenance and repair costs
• CoPilot, up to 15%
• CBS News, from as a little as 3% to as much as 10% or 12% fuel savings
• Varta Batteries, can achieve fuel savings of up to 15%
• Head and Shoulders up to 100% 🤣

So if we drive in ideal conditions for Stop/Start with long enough stops, but not too long and not too short, and we have frequent stops, ideally using only A and B roads and not dual carriageways and definitely not motorways it might just about be possible to save up to ????? Lets just say 5% and then factor in a new battery every 3 to 4 years and at least 3 or 4 visits to the dealer to complain when its not working. It certainly makes quite an impact on the emissions !!

 

 

2 minutes ago, unofix said:

Claims on the fuel savings (if any) are wide and varied suggesting that there is no definitive proof of what savings there are. Very much like those who claim that EV's are 'zero' emissions.

A quick look at some figures on claimed fuel savings are...

Aren't those figures similar to those often quoted by just having your tires at the correct pressure! 😆

Just now, StephenFord said:

Aren't those figures similar to those often quoted by just having your tires at the correct pressure! 😆

Yup !! 🤣

There is a video on YouTube that has done a fuel saving test with quoted figures but the tests that they did were so fundamentally flawed that they are wrong.

You only have to think about it logically for an engine not running vs running when stationary to at some point be worth turning off, just in terms of fuel savings. Else you might as well park and leave it running 24/7. 
 

It is for the emission tests, but if you’ve been stuck on the motorway stationary before, many will turn their engine off knowing it’s wasting fuel. 

It depends on how long the car is stationary for and it's unlikely to be a linear thing. There are no doubt a sweet windows but either side of that it is likely to be the opposite.

I have myself in years gone by, switched off the ignition when stuck in a traffic jam on a motorway. This should never be confused with the Stop/Start system merely killing the engine and leaving most electrical equipment operational.

With the engine off with the Stop/Start system a typical drain on the car battery is around 17 Amps (yes I have actually measured this). So just assuming a battery of 100Ah it could only supply this for around 6 minutes. Of course S/S will intervene after 3 minutes maximum and restart the engine otherwise there would be insufficient power for a restart. All that battery energy that was used when the engine was off didn't come for free. It now has to be put back in to the battery meaning the alternator and by default the engine will have to work harder and use more fuel.

There are many views on S/S and depending on where you're beliefs are, it will either seem like a God sent bit of technology OR, a complete white elephant and a poor attempt by the establishment to tick the 'Green Box'

30 minutes ago, unofix said:

I have myself in years gone by, switched off the ignition when stuck in a traffic jam on a motorway. This should never be confused with the Stop/Start system merely killing the engine and leaving most electrical equipment operational.

With the engine off with the Stop/Start system a typical drain on the car battery is around 17 Amps (yes I have actually measured this). So just assuming a battery of 100Ah it could only supply this for around 6 minutes. Of course S/S will intervene after 3 minutes maximum and restart the engine otherwise there would be insufficient power for a restart. All that battery energy that was used when the engine was off didn't come for free. It now has to be put back in to the battery meaning the alternator and by default the engine will have to work harder and use more fuel.

There are many views on S/S and depending on where you're beliefs are, it will either seem like a God sent bit of technology OR, a complete white elephant and a poor attempt by the establishment to tick the 'Green Box'

People also aren’t limited to one view or the other. I can see the potential benefits, still not particularly like it but also don’t really care half the time. 
 

In any case whether you want it to work or not, it’s not worth OP changing the battery for. I didn’t worry about stop start, I only changed my battery when I started getting keyless entry shutting off and infotainment messages about saving battery. That was my warning the battery needed changing. 

6 minutes ago, alexp999 said:

... That was my warning the battery needed changing. 

Hey, if you're in the market for a battery charger, I can recommend the  ... 🤣