Hi

I’m new here and would like some help please. I have a newer 2017 SMax which is great - except the auto stop start isn’t currently working. The dash menu tells me “Vehicle Running due to battery charging” whilst also showing the greyed out stop start icon.

Been to a dealer who did the recall on the battery monitor cable loom. They’ve since tested the battery which was Ok and done checks and confirm there is no issue with the vehicle except I’m not driving enough (which is a fair comment). However, after driving it away from the garage it still didn’t work even when they said it had been charged 🤔

I've charged the battery myself today with a smart AGM tester and it was full within 30mins.  The dash is still saying ... charging! I suspect the alternator, charging system and battery is ok but perhaps the battery monitor is faulty or needs calibration.  I’ve checked their new loom modification and it’s fuse and all feels ok.

Any ideas please!

I had the same issue with mine recently. A drive from moray down to fife cured it, approx. 160 miles in total. The start/stop started working as should, think the car just wants a good charge from itself and not an outside source. The system even started working as early as Dundee. 

35 minutes ago, Meta55 said:

I had the same issue with mine recently. A drive from moray down to fife cured it, approx. 160 miles in total. The start/stop started working as should, think the car just wants a good charge from itself and not an outside source. The system even started working as early as Dundee. 

Interesting thanks. I too did long drives last week ~280miles, twice, and it still wasn’t happy! Because of that is why I took it back in, thinking the recall works had caused a problem.

On 8/2/2020 at 10:35 PM, HiZ said:

Interesting thanks. I too did long drives last week ~280miles, twice, and it still wasn’t happy! Because of that is why I took it back in, thinking the recall works had caused a problem.

Hopefully it’s just a battery monitor reset. 

You may find that the BCM is not accurately measuring /monitoring the Battery's state of charge (SOC). 

My 2017 SMAX 2.0ltr TDI 150 also has this problem. I only noticed because the heated windscreen didn't work after about 3 mths of ownership, the start stop I deactivated on every drive because I don't like it as an engineer. The heated windscreen not working was  unhelpful as we suffer from heavy frosts during the winter which was the only reason I specced it for £400. 

I took it to Ford under warranty, no issues with the battery found, and when fully charged in the garage, the windscreen and SS worked perfectly! As soon as I would drive it home though, after one let cycle, neither would work! Ford were no help and said they couldn't condemn the battery under warranty as it charged full no issues. 

How did I discover the BCM is at fault? Because I wanted to understand what was wrong with my car, I ordered an OBDLink MX, set up BCM battery voltage (gives battery voltage and alternator output) and Battery SOC monitoring (a calculation by the BCM of what it thinks the battery charge state is in %). On showing Ford the evidence, they said as long as the battery charges and passes their battery check, there are no other faults present. They refused to change the BCM "as it is working at the dealership!",

 

They did tell me though that for the BCM to give an accurate battery SOC %, the car must be at rest (switched off and locked) for 8hrs or more. I found this to be complete rubbish, as one day the car would tell me it is at 88%, the next it would be 0%, the 34, then 0 or something else entirely.

If the battery SOC is under 75%, the BCM activates reduced functionality such as start stop and heated windscreens not working as the car is trying to recharge the battery. If you get into the car but don't start it, it will also time out the dash much quicker and display the message, Power saving - System off to preserve battery (or words to that effect. 

I now charge my car overnight once or twice a month to make sure the battery is as healthy as I can. Randomly, the car will re-engage start stop etc, but on next start it'll read Battery SOC as 30% and all is back to paper saving. 

I haven't bothered to buy a new BCM as I do not believe it will change things. Massively frustrating as I even changed the battery for a larger capacity AGM unit, thinking a new battery and a BCM reset for new battery might fix it. It had no effect. That was a wasted £150 as the original battery still started without issue or struggle. 

Get yourself a little OBDLink MX+ module, plug it in, set up the Car Scanner Pro app (use OBDLinks own to set it all up first), then select battery voltage and battery SOC as items to monitor. That'll show you straight away what the BCM believes the SOC is. If it is below 75%, there is no Start stop or heated windscreen. 

I had 3 Skoda's before this SMax, all with heated windscreens. All three ran the exact same use cycle as my SMax does now, not one had issues with SS or the heated windscreen. The last Superb at 3 years old had all the bells n whistles and just worked! 

Best of luck figuring this all out. Ford couldn't or wouldn't, and I wasn't prepared to drop more money into the car to potentially solve nothing!

3 minutes ago, blahde2 said:

You may find that

the thread has been dead for 4 years

No worries, hoping someone reads it and gives me a solution that fixes this issue, other than my monitoring one. 

On 9/29/2024 at 4:47 PM, blahde2 said:

You may find that the BCM is not accurately measuring /monitoring the Battery's state of charge (SOC). 

My 2017 SMAX 2.0ltr TDI 150 also has this problem. I only noticed because the heated windscreen didn't work after about 3 mths of ownership, the start stop I deactivated on every drive because I don't like it as an engineer. The heated windscreen not working was  unhelpful as we suffer from heavy frosts during the winter which was the only reason I specced it for £400. 

I took it to Ford under warranty, no issues with the battery found, and when fully charged in the garage, the windscreen and SS worked perfectly! As soon as I would drive it home though, after one let cycle, neither would work! Ford were no help and said they couldn't condemn the battery under warranty as it charged full no issues. 

How did I discover the BCM is at fault? Because I wanted to understand what was wrong with my car, I ordered an OBDLink MX, set up BCM battery voltage (gives battery voltage and alternator output) and Battery SOC monitoring (a calculation by the BCM of what it thinks the battery charge state is in %). On showing Ford the evidence, they said as long as the battery charges and passes their battery check, there are no other faults present. They refused to change the BCM "as it is working at the dealership!",

 

They did tell me though that for the BCM to give an accurate battery SOC %, the car must be at rest (switched off and locked) for 8hrs or more. I found this to be complete rubbish, as one day the car would tell me it is at 88%, the next it would be 0%, the 34, then 0 or something else entirely.

If the battery SOC is under 75%, the BCM activates reduced functionality such as start stop and heated windscreens not working as the car is trying to recharge the battery. If you get into the car but don't start it, it will also time out the dash much quicker and display the message, Power saving - System off to preserve battery (or words to that effect. 

I now charge my car overnight once or twice a month to make sure the battery is as healthy as I can. Randomly, the car will re-engage start stop etc, but on next start it'll read Battery SOC as 30% and all is back to paper saving. 

I haven't bothered to buy a new BCM as I do not believe it will change things. Massively frustrating as I even changed the battery for a larger capacity AGM unit, thinking a new battery and a BCM reset for new battery might fix it. It had no effect. That was a wasted £150 as the original battery still started without issue or struggle. 

Get yourself a little OBDLink MX+ module, plug it in, set up the Car Scanner Pro app (use OBDLinks own to set it all up first), then select battery voltage and battery SOC as items to monitor. That'll show you straight away what the BCM believes the SOC is. If it is below 75%, there is no Start stop or heated windscreen. 

I had 3 Skoda's before this SMax, all with heated windscreens. All three ran the exact same use cycle as my SMax does now, not one had issues with SS or the heated windscreen. The last Superb at 3 years old had all the bells n whistles and just worked! 

Best of luck figuring this all out. Ford couldn't or wouldn't, and I wasn't prepared to drop more money into the car to potentially solve nothing!

Exact same issue I’m having with my Smax ST 68 plate. Ford changed the battery twice, claiming that was the issue, but the stop start and heated windscreen have stopped again, despite 1 drive to south France from UK and back.

At a loss now, as I think it’s just a really poor system design by Ford but they won’t admit to it.

26 minutes ago, Cloudlightning said:

despite 1 drive to south France from UK and back.

There is a common misconception that driving long distances charges the battery. While that was certainly very true for cars before 2005, it most definitely is not true for newer models especially those built after 2017.

Due to ever tighter emissions regulations manufacturers were forced to do everything possible to meet impossible government targets. One trick used is to firstly only charge the car battery to a maximum of 80% of it's capacity. Secondly only use the alternator to charge the battery on engine 'overrun' ie. when slowing down, or when going down a hill. This results in the battery State Of Charge gradually getting lower and lower as the weeks go by. Long gone are the days when a 50 mile run down the motorway would recharge the battery. The 'Smart' charge systems used on most modern cars cares little for how long or how fast the car is driven, only about how much the alternator can be used to slow the engine when reducing speed and hence charging the battery with zero emissions.