FORScan forum

No, i mean how long does your s/s work since you've changed the battery type = number of days since the change
For me, battery type change had zero effect on the SoC value (and therefore s/s operation). But changing battery type resets BMS and before SoC value fails again, s/s may work for some time.

My personal experience with following setting:

Battery: Varta 70Ah 760CAA
BCM: BCJ
BMS: CB
Battery Type in BCM: Varta 70Ah 600CCA
SoC: 90%

This was working a few months (maybe 5-6 months) until S/S stopped working again. The battery isnt charging enough to even reach the 90%. I observed this with ForScan during driving. The battery charging stopped at 60-70%. Why this happened i dont know.

So the last option for me was: Install a brand new battery and run it with the latest BCM Version. I think the BCM Calibration is the most important value! In the firmware is the actual loading strategy. Maybe the battery setting changes a bit of the loading strategy. The BMS is a sensor, which could send false values. As mine is the latest built I dont think it is the reason.

I will try this now:

New Configuration:

Battery: Banner 75Ah 700CCA (brand new)
BCM: BJC (latest available calibration)
BMS: CB (latest available BMS Sensor)
Battery Type in BCM: Exide 80Ah 700CCA
SoC: 90%

When the same problem appears again I really dont know what to do anymore. But I will keep you updated.

Anduril wrote: Wed Oct 26, 2022 11:16 am No, i mean how long does your s/s work since you've changed the battery type = number of days since the change
For me, battery type change had zero effect on the SoC value (and therefore s/s operation). But changing battery type resets BMS and before SoC value fails again, s/s may work for some time.

I changed it on the 10th of September and it's been working ever since.
The car was built in January of 2020 and I am still on the original battery.

Did not look in to what the SoC was but as long as the S/S is working correctly I don't mind what the computer reports the SoC as.

On my MK3 I read that the car determines the SoC after the car has been off for at least 9 hours.

New battery installed now.. charged it with an external charger to 100% and reset the BMS. Now we will see..

What an excellent post, I’m watching as we have a 2021 focus st edition, and 2 fiesta St’s all have the same issues all are under warranty.

There is a new battery monitor sensor out with the ending -CC. This updated version should also be a part of the solution. I already installed the newest BMS and combined with the other tasks its working now at my car.

Did you change it yourself or was it warranty service?

I bought it by myself and installed it as my dealership wont believe me anything and treat me like a fool. They didnt want to change my BMS, battery or update the BCM. So I did all by myself.

Actually as I know its also a warranty service under the TSI 22-2422. So it should be paid by ford. The BMS cost about 60€ or Dollars.

Battery State of Charge

During the drive cycle the Electrical Energy Management software will adjust the initial battery state of charge by monitoring the
charge and discharge current and adjusting the state of charge up during charging, and down during discharge. During rest
periods (key off with no electrical loads) when the vehicle enters sleep mode, the battery voltage is sampled to recalibrate the
State of Charge. The Battery monitoring sensor automatically executes this recalibration anytime the vehicle enters sleep mode
and when the total vehicle current draw is below 300mA. It takes 4 to 6 hours in the sleep mode to recalibrate the battery state
of charge to high accuracy. If the system draw does not allow the battery state of charge recalibration over the previous 7 to 10
days the State of Charge quality factor will change to flag this and some Electrical Energy Management Functions which rely on
the accuracy of the battery state of charge may be temporarily turned off until a recalibration takes place.
NOTE: Any devices left attached to the power socket that draw in excess of 200mA (or less depending on other battery loads)
will prevent a battery monitoring sensor to recalibrate the battery state of charge.

After the BMS reset, let the battery rest for at least 3 hours and then connect the external charger to the battery to fully charge it!! For BMS to establish 100% SOIC. You have MAX 7 days from BMS reset. And everything will be fine later. It helped me

it is also important that after the battery is fully charged, do not put the car in standby mode for at least 3 hours after a full charge. so that BMS can easily dump the battery energy to 80% and calculate Soc. carry out calibrations in this way once every 3 months