Lincoln Aviator: High Voltage Battery, Mounting and Cables / Description and Operation - High Voltage Battery, Mounting and Cables - Plug-In Hybrid Electric Vehicle (PHEV) - System Operation and Component Description

System Diagram

System Operation

  Network Message Chart - Battery Energy Control Module (BECM)

Cell Balancing

Individual cells can deviate over the life of the high voltage battery. The purpose of cell balancing is to equalize the individual cell charges. By balancing the cells the high voltage battery maintains top efficiency. The BECM continuously monitors individual battery cell voltages and will perform balancing when required and when certain conditions are met. The high voltage battery SOC (State of Charge) must be equal or greater than 15% with the ignition off. The cell balancing will occur for a duration of 24 hours. The ignition key must be cycled for the balancing to start a new 24 hour cell balancing period. When cell balancing is performed BECM discharges individual cells with the highest voltage to match the remaining cells.

Vehicle Shut Down

A vehicle shut down signal is sent by the BECM when the BECM is about to open the contactors due to an internal fault or has just opened the contactors due to an external input (external module commanding contactors to be opened such as a crash event or interlock circuit failure). When vehicle shut down occurs, the Stop Safely warning indicator is illuminated warning that the vehicle will be shut down within a matter of seconds and the operator should pull off the road as soon as possible. Depending on the fault condition that lead to the shutdown, the vehicle may or may not restart if the condition has corrected itself. If the fault condition is severe enough, the fault will have to be repaired and Diagnostic Trouble Codes (DTCs) cleared before the vehicle will restart.

Component Description

High Voltage Battery

The high voltage battery consists of pouch cells packaged into modules which deliver approximately 355 volts DC to the high voltage system. The high voltage battery supplies electrical energy to the electric motor to move the vehicle when it is operating in electric mode only or to assist the Internal Combustion Engine (ICE) (heavy acceleration). When the engine is operating or the vehicle is moving, the electric motor can be used as a generator creating high-voltage AC electricity. High-voltage AC generated by the electric motor is converted to high voltage DC by the SOBDMC and transmitted through the high voltage cables to recharge the high voltage battery.

The high-voltage DC electrical power is converted to low voltage DC electrical power through the Direct Current/Direct Current (DC/DC) converter control module. This low-voltage high current DC electrical power is then supplied to the 12-volt batteries through the low voltage battery cables.

The high-voltage system has a floating ground. The floating ground is designed to completely isolate the high-voltage system from the vehicle chassis. The high-voltage cables are fully insulated (isolated) from all vehicle components and circuits. There are no common connections (such as body grounds) used to conduct the high-voltage power. The BECM monitors this system for any leakage of current to the normal electrical system (similar to a household ground fault interrupter). There are high voltage circuits from the battery cell arrays to the BECM used to monitor isolation resistance between the high voltage battery and chassis.

Battery Energy Control Module (BECM)

The BECM manages the condition of the high voltage battery to control its charging and discharging. The BECM controls the high voltage battery coolant pump in conjunction with BCMC controlling the diverter valve via a HS-CAN request from the SOBDMC. When additional high voltage battery cooling is needed (high ambient temperatures and/or during high current flow demand) the coolant diverter valve is energized to allow coolant to be diverted through the high voltage battery chiller. The high voltage battery chiller is part of the HVAC system used to chill the coolant prior to being returned to the high voltage battery.

The BECM monitors the individual cell voltages and temperature sensors internal to the battery arrays. The BECM monitors the battery current using a sensor located in the high voltage battery junction box. This information is needed by the BECM to control the high voltage battery and determine its ability to receive and provide power to the vehicle. The BECM communicates with other vehicle modules on the HS-CAN.

The BECM receives the following hard-wired inputs:

• HEV (Hybrid Electric Vehicle) wakeup
• High voltage battery connector interlock status
• High voltage battery contactor control supply voltage (includes the service disconnect)
• High voltage battery cells sense leads
• High voltage battery cell temperature sensors
• High voltage battery coolant inlet temperature sensor
• High voltage battery coolant pump feedback signal
• Motor electronics coolant pump feedback signal
• Current sensor (part of the high voltage battery junction box)
• Event notification status from the RCM
• HS-CAN

The BECM provides the following outputs:

• High voltage battery coolant pump PWM control signal
• Motor electronics coolant pump PWM control signal
• High voltage battery junction box pre-charge contactor control
• High voltage battery junction box positive contactor control
• High voltage battery junction box negative contactor control
• High voltage battery junction box auxiliary contactor control
• HEV (Hybrid Electric Vehicle) wakeup
• HS-CAN information

Direct Current/Direct Current (DC/DC) Converter Control Module

The DCDC is an liquid-cooled component that converts high voltage (192-413 volts) DC power to low-voltage (12 volt) DC power. The converter provides power to the vehicle 12-volt battery and low-voltage electrical systems. The PCM requests the Direct Current/Direct Current (DC/DC) converter control module to enable power conversion through an enable message over HS-CAN. The PCM sends a charging voltage setpoint request over HS-CAN to the Direct Current/Direct Current (DC/DC) converter control module. For information on the DCDC,
Refer to: Direct Current/Direct Current (DC/DC) Converter Control Module - System Operation and Component Description (414-05 Voltage Converter/Inverter, Description and Operation).

Hybrid Electric Motor Assembly

The hybrid electric motor assembly is mounted to the front of the transmission assembly and is also used as a generator. The assembly also incorporates an electric operated engine disconnect clutch that engages or disengages the electric motor from the Internal Combustion Engine (ICE).

The electric motor generates high voltage electricity for charging the high voltage battery. The engine is started using either conventional engine block mounted starter (for cold starts only) and a Belt Integrated Starter Generator (BISG) for other starts during normal vehicle operation. The electric motor must be energized and rotated to match Internal Combustion Engine (ICE) cranking speed during starting. If the high voltage system is shutdown due to a malfunction the Internal Combustion Engine (ICE) will not start and the vehicle will be disabled.

The electric motor is used to accelerate the vehicle from a stop when driving under electric power. The electric motor is also used to recover energy during regenerative braking. The electric motor receives power from the high voltage battery after the high voltage battery junction box contactors have closed. For information on the electric motor and its operation,
Refer to: Electric Motor (303-01C Electric Motor, Description and Operation).

During braking and deceleration events the regenerative brake system utilizes the electric motor as a generator to create and capture electrical current. This captured energy is used to charge the high voltage battery. If the high voltage battery is adequately charged, the captured energy is used for Internal Combustion Engine (ICE) braking to slow the vehicle. The regenerative brake system is a series system which the generator braking is used first, up to the limits of the generator torque capacity and the high voltage battery charging capacity. After optimum regeneration is used, the friction brakes are applied to supplement braking demands. For information on regenerative braking,
Refer to: Anti-Lock Brake System (ABS) and Stability Control - System Operation and Component Description (206-09 Anti-Lock Brake System (ABS) and Stability Control, Description and Operation).

High Voltage Battery Junction Box

The high voltage battery junction box houses the 4 contactors (precharge, main positive, main negative, and auxiliary negative) which, when commanded closed by the BECM, connect the high voltage battery to various components for high-voltage consumption and/or charging of the high voltage battery. During initial power up after the negative contactors (main negative and auxiliary negative) are closed, the precharge contactor closes prior to the positive contactor which routes high voltage through the precharge resistor which is also located in the high voltage battery junction box. This reduces the in rush current to prevent contactor damage. The high voltage battery junction box design distributes high-voltage via three circuits to various high voltage components. The high voltage battery has three high voltage negative outputs and shared high voltage positive output. The single high voltage high current circuit supplies the negative polarity to the SOBDMC also known as the Inverter System Controller (ISC) and is protected by a high voltage 300A fuse. One high voltage low current circuit supplies the negative polarity to the DCDC and SOBDM also known as the Battery Charger Control Module (BCCM) and is protected by a high-voltage 40A fuse and a separate high voltage low current circuit supplies negative polarity to the Cabin Coolant Heater and ACCM and is protected by a second high-voltage 40A fuse. The high current positive side is shared with all the high voltage components. Any fault resulting in excessive current on a low current circuit will open the affected 40A fuse first and stop power distribution to the components on that circuit. Any fault resulting in excessive current on the high current circuit will open the 300A fuse and stop power distribution to the SOBDMC. Note the high voltage fuse current ratings reference the operating current of the circuit and not the faulted current to open the high voltage fuse. The high voltage battery junction box contains the contactors, the current sensor, high-voltage high current 300A fuse, and two high-voltage low current 40A fuses.

The high voltage battery junction box contains a current sensor that is hardwired to and monitored by the BECM. The current sensor helps determine the load or rate of charge of the high voltage battery by sensing current flow into or out of the high voltage battery. The high voltage battery junction box also contains voltage sense points downstream of the high voltage contactors that are used to detect issues with the contactors.

High Voltage Cable Assembly

All cables that carry high voltage are integrated into two high-voltage cable assemblies. The primary high-voltage cable connects the high voltage battery, SOBDMC, DCDC, SOBDM and the cabin coolant heater. Another high voltage cable connects the ACCM to the primary high voltage battery cable. There are 4 circuits that connect to the High Voltage Battery. Two main circuits supply high voltage to the SOBDMC. Two separate high voltage low current circuits supply negative polarity to the DCDC and the Cabin Coolant Heater. The DCDC acts as a junction and sends high voltage to the SOBDM and the Cabin Coolant Heater acts as a junction for the other low current circuit and sends high voltage to the ACCM. There is a separate 3 phase AC high voltage cable assembly that connects the hybrid electric motor assembly and the SOBDMC.

High Voltage System Service Disconnect Plug

The high voltage system uses a low voltage disconnect plug that opens the 12-Volt contactor control supply circuit and is located in the engine compartment. When the service disconnect plug is disconnected the high voltage battery contactors that supply high voltage to the vehicle are unable to close. The high voltage system must be depowered prior to disconnecting any high voltage cable (identified by orange color).
Refer to: High Voltage System De-energizing (414-03A High Voltage Battery, Mounting and Cables, General Procedures).