Read in full before even thinking of doing this. Do not ask me if you should do it, read the below.
The BMS is equipped to vehicles which have Smart Regenerative Charging (SRC) or Start/Stop system. These systems require knowledge of the battery State of Charge (SoC). The BMS is the sensor used to provide this information.
The BMS continuously monitors the voltage, current and temperature of the battery. BMS uses these values to calculate Soc and State of Health (SoH).
Method to reset BMS
NOTE: Do not conduct the reset unless a battery has been replaced, refer to "When should the BMS be factory reset?" in FAQ later in this bulletin.
NOTE: The method to reset BMS is for Ford internal use only and should never be provided to the vehicle owner.
When should the BMS be factory reset?
BMS is unable to detect what type or size battery is built into the vehicle therefore it is important to always exchange the built-in battery with a battery of the same type and size.
BMS is also unable to detect the difference between replacement of an old battery with a new part and reconnection of the original battery. Therefore when replacing the battery it is important to perform diagnostic reset on BMS to clear any accumulated battery ageing data, as it is not done automatically.
Failure to perform a diagnostic reset on BMS after replacement of the battery can result in BMS estimating the parameters wrongly and disabling the
Start/Stop system and SRC.
To ensure correct BMS functionality, it is important to reset the BMS when an old battery has been replaced with a new part. This must not be done
for any other reason.
NOTE: A BMS diagnostic reset does not reset the Soc level reported by the module - it only clears accumulated ageing data. Disconnecting the BMS from power and then reconnecting (also known as Power-on-reset) results in Soc level re-calculation. However, this does not clear any ageing data.
The BMS can be reset in two ways:
- Using the function within the Integrated Diagnostic System (IDS). IDS> Body > BMS Reset.
- By pressing vehicle buttons in the sequence as described below.
If the vehicle has a rear fog light switch:
1. Enter the vehicle and perform the steps 2 to 4 below within 10 seconds.
2. Switch ignition ON, engine OFF (Position II).
3. Push and release the rear fog light switch 5 times.
4. Push and release the hazard warning light switch 3 times.
5. If successful the charging system warning light on the Instrument Panel Cluster (IPC) will blink 3 times within the next 15 seconds.
6. BMS reset done.
If the vehicle does NOT have a rear fog light button:
1. Enter the vehicle and perform the steps 2 to 4 below within 10 seconds.
2. Switch ignition ON, engine OFF (Position II).
3. Pull and release the high beam switch 5 times.
4. Press and release the brake pedal 3 times.
5. If successful the charging system warning light on the IPC will blink 3 times within the next 15 seconds.
6. BMS reset done.
How does the BMS work?
The sensor measures temperature, voltage and current throughput of the battery. It uses this information to calculate the battery Soc and SoH. To function with high accuracy, the BMS must be recalibrated at regular intervals. A recalibration occurs during a rest period when the battery quiescent current is less than 100mA. This rest period must last for at least 3 hours. The longer the rest period, the greater the accuracy. The timeframe in which a recalibration must take place is seven days. If the system has been unable to carry out a recalibration within 7 days, the SoC accuracy cannot be guaranteed. This will result in the Start/Stop and SRC systems being deactivated. These systems will also be disabled if the sensor detects the battery is reaching its end of life, low state of charge or health.
