Functional Description - Battery Pack Control Module (BPCM)

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The Battery Pack Control Module (BPCM) is an electronic control module integrated with the high voltage (HV) battery. The BPCM includes the Analog/Digital (A/D) circuitry for the internal input/output controls and Controller Area Network (CAN) communications. The BPCM monitors and manages the voltage, current and temperature of the HV battery.

BPCM inputs include:

Inlet coolant temperature sensor
Outlet coolant temperature sensor
IDCM coolant inlet temperature sensor
HV wake up signal
Individual cell voltage and temperature
Current sensor
High Voltage Interlock Loop (HVIL) source signal
High Voltage Interlock Loop (HVIL) return signal

The BPCM responsibilities include:

Component protection
Report HV battery system status
ePT wake up
Battery State Of Charge (SOC)
Providing current and voltage limits during driving and charging
Controlling the three contactors
Maintaining the battery cells at an appropriate temperature to ensure the usage life of the battery
Providing loss of isolation monitoring
Providing High Voltage Interlock Loop (HVIL) monitoring
Battery coolant pump operation via LIN communication
Controlling the State Of Charge (SOC) indicator status
Diagnostics (OBD/ On-Board Diagnostics II)

LIMP MODE

If there is an issue with the Battery Management System (BMS) the vehicle will enter a "limp" mode. Vehicle performance will be reduced in order to protect ePT components. When the BPCM determines that a fault exists, it sends a message to the Hybrid Control Processor (HCP). The HCP will then request that the Instrument Panel Cluster (IPC) display a reduced performance message to the driver. Faults that may cause a limp mode are:

Cell voltage sensor faults
Cell temperature sensors faults
Current sensor faults

Limp mode can be caused by too hot or too cold battery temperature extremes:

Vehicle will be put into Electric Vehicle (EV) mode if not already
Stay in EV mode until HV battery SOC is too low then initiate hybrid mode, but in a powertrain reduced performance mode, meaning power limited ~ 40 km/h (25mph).
It will remain in hybrid mode until SOC is acceptable to return to EV mode.
Depending on the BPCM failure, charging may not be allowed

Courtesy of CHRYSLER GROUP, LLC

BATTERY LOSS OF ISOLATION DETECTION

Isolation resistance is measured between the battery positive/negative terminals and the vehicle ground. The isolation sense circuits compare the stepped down HV and compares it to a reference point internal to the BPCM.

The isolation sense points (VA and VB in the diagram) will measure 2.5 volts reference value when the top and bottom switches are open. When the top switch is closed and the bottom switch is open, the isolation VA sense voltage will shift from the 2.5-volt and when the bottom switch is closed and top switch is open, the isolation VB sense voltage will shift from the 2.5-volt. These two shifted values of isolation sense voltages (difference between the corresponding isolation sense voltage and the 2.5-volts) are used to calculate the isolation resistance.

If the contactors are open, the isolation resistance calculated will be the internal battery isolation resistance and if the contactors are closed, the isolation resistance calculated will be the external vehicle isolation resistance.

The isolation sensor diagnostic monitors the isolation detection circuit performance, while the system isolation diagnostic monitors the vehicle isolation resistance. Battery side isolation diagnostic monitors the battery pack internal isolation resistance, to be within the normal operating ranges. When the measurements reach or exceed any of the limits, the diagnostics will be considered failing. The diagnostics run continuously after power up, as long as the enable conditions are met. The diagnostics only need to run and fail once per trip, in order to fail the test.

The purpose of the isolation sensor circuit diagnostic is to detect the isolation circuit performance faults, while the isolation diagnostics purpose is to detect the loss of isolation for both the vehicle and the internal battery pack.

P0AA7: Hybrid Battery Voltage Isolation Sensor Circuit - This diagnostic performs the isolation resistance measurement circuit check.

P0AA6: Hybrid Battery Voltage System Isolation Fault - This diagnostic performs the vehicle side isolation resistance check and detects a fault when the isolation resistance on the vehicle side is less than a calibrated threshold.

P1E1B: Hybrid/EV Battery Side Voltage System Isolation - This diagnostic performs the Battery side isolation resistance check. The fault is detected and set when the isolation resistance on the battery side is less than a calibrated threshold.