Battery Management System

WARNING: This page is about a different car, the 2015 Lincoln MKS. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: When any vehicle module is being programmed, connect an external battery charger to make sure the module programming is completed without the interruption due to the load shedding feature becoming active. The external battery charger must maintain a system voltage above 13 volts. This may require a charger setting higher than the lowest charge setting. The external battery charger negative connection must be made to an engine or vehicle chassis ground and not the negative battery terminal. If the connection is to the negative battery terminal, load shedding cannot be prevented from being invoked and module programming may be corrupted. After charging has begun, start the engine to clear any load shed states and then turn the engine off and proceed with programming.

This vehicle is equipped with load shed strategy. The BCM monitors the battery state of charge using the battery current sensor attached to the negative battery cable and the system voltage supplied to the BCM during 8 continuous hours of vehicle sleep time (key off with doors closed).

To maintain correct operation of the load shed system, ground any electrical devices or equipment to the chassis ground and not the negative battery terminal. A connection to the negative battery terminal may cause an inaccurate measurement of the battery state of charge and may cause incorrect load shed system operation.

Engine Off Load Shed

The BCM uses the battery current sensor to keep track of the battery state of charge. The battery current sensor is a Hall-effect sensor attached to the battery ground cable. When the engine is off and the BCM determines the battery state of charge is below 40%, or 10% of the charge has been drained, or 45 minutes have elapsed, a load shed message is sent over the CAN. This message turns off the audio/navigation system to save the remaining battery charge. Under this condition the FCDIM (without touchscreen controls) displays SYS OFF TO SAVE BATT or the FDIM (with touchscreen controls) displays BATTERY SAVER - SYSTEM OFF PLEASE START THE ENGINE to notify the driver that battery protection actions are active.

Engine off load shedding occurs when the engine is not running and the ignition is in the ACC, RUN or delayed accessory position. This load shed state clears once the vehicle has been started and the battery state of charge recovers. If the engine off load shed occurs, the audio/navigation system turns off.

When the ignition is in the RUN position and if load shed occurs, the IPC message center may display either TURN POWER OFF TO SAVE BATT (base message center) or TURN POWER OFF TO SAVE BATTERY (optional message center). The audio/navigation system shuts down after the message center displays the warning.

If a fault occurs with the battery current sensor or circuit(s), the only engine off load shed strategy that is active is a 45 minute timer. After 45 minutes have elapsed, the audio/navigation system turns off. To clear the load shed state, restart the engine.

For charging the vehicle battery, REFER to Battery, Mounting and Cables .

If the vehicle battery is charged by connecting the battery charger to the battery negative terminal or the battery is replaced , carry out the BMS Reset using the scan tool. If the BMS Reset is not carried out, it takes approximately 8 hours for the BCM to learn the new battery state of charge. During this 8 hour period, the vehicle must be undisturbed, with no doors opened or keyless entry button presses. If the vehicle is used before the BCM is allowed to learn the new battery state of charge, engine off load shedding can still occur and a message may display.

If the vehicle battery is charged by connecting the battery charger to the engine or chassis ground , the BMS Reset using the scan tool is not necessary.

If the vehicle has been jump started , test the battery condition. REFER to Battery, Mounting and Cables .

Engine Running Load Shed

When the BCM and/or PSCM voltage is low, with the engine running, the BCM sends a message to either minimize or shut down the climate controlled seats, rear defrost, heated mirrors and DATC blower motor to improve system voltage. Under this condition, the IPC message center displays either LOW BATTERY LESS FEATURES (base message center) or LOW BATTERY FEATURES TEMPORARILY TURNED OFF (optional message center) to notify the driver that battery protection actions are active.

There are 3 states of engine running load shed:

Load shed 1
Load shed 2 transient
Load shed 2 continuous

Load Shed State	Entry Conditions	Impact to Features	Clear Conditions
Load shed 1	If vehicle speed is below 16 km/h (10 mph) If vehicle speed is above 16 km/h (10 mph) Voltage to the PSCM is less than 11.5 volts. PSCM measures current draw greater than 0 amps. Voltage to the BCM is less than 11.6 volts.	Climate controlled seats switch from HIGH to MED. If they are already at MED, the state does not change.	Voltage to the BCM is greater than 12.7 volts or the generator field duty cycle is less than 88%.
Load shed 2 transient	Voltage to the PSCM is less than 11.0 volts. PSCM measures current draw greater than 20 amps.	If equipped, climate controlled seats are disabled, but the indicators remain illuminated. If equipped, rear defrost and heated mirrors are disabled, but the indicator remains illuminated.	Voltage to the BCM is greater than 12.4 volts.
Load shed 2 continuous	Vehicle was in load shed 2 transient state for greater than 20 seconds.	If equipped, climate controlled seats are disabled and the indicators are off. If equipped, rear defrost and heated mirrors are disabled and the indicator is off. If equipped with DATC, the blower motor is reduced to 50% speed and the blower speed indicator reflects this. If equipped, DC/AC inverter (AC powerpoint) is disabled. The base message center displays LOW BATTERY LESS FEATURES. The optional message center displays LOW BATTERY FEATURES TEMPORARILY TURNED OFF.	Voltage to the BCM is greater than 12.4 volts for more than 60 seconds.