Principles of Operation

High-Voltage Traction Battery

Principles of Operation

The High Voltage Traction Battery (HVTB) consists of D-cell type batteries packaged into modules which deliver approximately 275 volts DC to the high-voltage system. The HVTB (High Voltage Traction Battery) provides cranking power to the high-voltage generator motor inside the Electronically Controlled Continuously Variable Transmission (eCVT). The HVTB (High Voltage Traction Battery) also supplies electrical energy to the traction motor (also internal to the eCVT (Electronically Controlled Continuously Variable Transmission)) to propel the vehicle when it is operating in electric mode only or to assist the gasoline engine (heavy acceleration). When the engine is operating or the vehicle is moving, the high-voltage generator motor generates high-voltage AC electricity. High-voltage AC generated by the generator motor can be used by the traction motor or to re-charge the HVTB (High Voltage Traction Battery).

When the HVTB (High Voltage Traction Battery) is being charged, high-voltage is converted from high-voltage AC to high-voltage DC electrical power inside the eCVT (Electronically Controlled Continuously Variable Transmission) and transmitted through the high-voltage cables to the HVTB (High Voltage Traction Battery).

The high-voltage DC electrical power is converted to low-voltage DC electrical power through the DC to DC Converter Control Module (DC/DC). This low-voltage high-current DC electrical power is then supplied to the 12-volt battery 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 Battery Energy Control Module (BECM) monitors this system for any leakage of current to the normal electrical system (similar to a household ground fault interrupter).

Battery Energy Control Module (BECM)

The BECM (Battery Energy Control Module) manages the condition of the HVTB (High Voltage Traction Battery) to control its charging and discharging. The BECM (Battery Energy Control Module) also manages the cooling of the HVTB (High Voltage Traction Battery) by controlling a fan attached to the HVTB (High Voltage Traction Battery) cooling outlet duct. The BECM (Battery Energy Control Module) communicates with other vehicle modules on the High Speed Controller Area Network (HS-CAN) bus.

The BECM (Battery Energy Control Module) receives the following hard-wired inputs:

- HVTB (High Voltage Traction Battery) interlock status

- Battery Pack Sensor Module (BPSM) information and status, via a dedicated (not accessible by a scan tool) CAN (Controller Area Network) between the BECM (Battery Energy Control Module) and BPSM (Battery Pack Sensor Module)

- Immediate shutdown request from the Transmission Control Module (TCM)

- Event notification status from the Restraints Control Module (RCM)

- Vehicle HS-CAN (High Speed Controller Area Network)

- BPSM (Battery Pack Sensor Module) power, ground and control circuits

- HVTB (High Voltage Traction Battery) inlet air temperature sensor

- HVTB (High Voltage Traction Battery) cooling fan feedback

The BECM (Battery Energy Control Module) provides the following outputs:

- HVTB (High Voltage Traction Battery) cooling fan Pulse Width Modulated (PWM) supply voltage

- Vehicle HS-CAN (High Speed Controller Area Network) information

The BECM (Battery Energy Control Module) receives HS-CAN (High Speed Controller Area Network) messages from the following modules:

- PCM

- TCM (Transmission Control Module)

- Instrument Panel Cluster (IPC)

- RCM (Restraints Control Module)

- DC/DC (DC to DC Converter Control Module)

The PCM HS-CAN (High Speed Controller Area Network) messages received by the BECM (Battery Energy Control Module) include:

- Gas engine status (running or off)

- Contactor control request status

- Current vehicle mode (power up, engine wait, shutdown, etc.)

- Ready light request

- Battery estimated current

- Transaxle gear position

- R-Mode Rebalance enable request

- Engine speed

- Throttle plate position

- Engine coolant temperature

- Ambient air inlet temperature

The TCM (Transmission Control Module) HS-CAN (High Speed Controller Area Network) messages received by the BECM (Battery Energy Control Module) include:

- Vehicle speed, via the TCM (Transmission Control Module)

- TCM (Transmission Control Module) high-voltage input, via the TCM (Transmission Control Module)

The DC/DC (DC to DC Converter Control Module) HS-CAN (High Speed Controller Area Network) messages received by the BECM (Battery Energy Control Module) include:

- DC/DC (DC to DC Converter Control Module) high-voltage input

- DC/DC (DC to DC Converter Control Module) high-voltage current

- DC/DC (DC to DC Converter Control Module) low-voltage input

- DC/DC (DC to DC Converter Control Module) over-temperature status

- DC/DC (DC to DC Converter Control Module) operation status

Battery Pack Sensor Module (BPSM)

The BPSM (Battery Pack Sensor Module) communicates with the BECM (Battery Energy Control Module) over a dedicated (not accessible by a scan tool) CAN (Controller Area Network) bus. The BPSM (Battery Pack Sensor Module) provides the current, voltage and temperature status of the HVTB (High Voltage Traction Battery) to the BECM (Battery Energy Control Module). This information is needed by the BECM (Battery Energy Control Module) to control the HVTB (High Voltage Traction Battery) and to determine the HVTB (High Voltage Traction Battery) ability to receive and provide power to the vehicle.

DC to DC Converter Control Module (DC/DC)

The DC/DC (DC to DC Converter Control Module) converter is a liquid-cooled component that converts high-voltage (179-343 volt) 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 controls the operation of the DC/DC (DC to DC Converter Control Module) through an enable message from the PCM to the DC/DC (DC to DC Converter Control Module). For information on the DC/DC (DC to DC Converter Control Module) , refer to Hybrid Drive Systems.

Electronically Controlled Continuously Variable Transmission (eCVT)

The eCVT (Electronically Controlled Continuously Variable Transmission) includes an internal generator motor and an internal traction motor. For information on the eCVT (Electronically Controlled Continuously Variable Transmission) and its operation, refer to Automatic Transmission/Transaxle &/or Transmission Control Systems and Computers and Control Systems Information.

The eCVT (Electronically Controlled Continuously Variable Transmission) generator motor generates high-voltage electricity for charging of the HVTB (High Voltage Traction Battery) and/or providing power to the traction motor. The generator motor is also used to start the gas engine. The generator motor is an internal part of the eCVT (Electronically Controlled Continuously Variable Transmission) and it cannot be repaired, only installed new as an assembly.

The eCVT (Electronically Controlled Continuously Variable Transmission) traction motor is used to accelerate the vehicle from a stop when driving under electric power. The traction motor is also used to recover energy during regenerative braking. The traction motor receives power from the HVTB (High Voltage Traction Battery) and/or from the eCVT (Electronically Controlled Continuously Variable Transmission) generator motor. The traction motor is an internal part of the eCVT (Electronically Controlled Continuously Variable Transmission) and it cannot be repaired, only installed new as an assembly.

The regenerative braking system is designed to recapture some of the energy from braking and deceleration events. It accomplishes this through the use of the traction motor and generator motor. This recaptured energy is used to charge the HVTB (High Voltage Traction Battery). If the HVTB (High Voltage Traction Battery) is adequately charged, the recaptured energy is used for gas engine braking to slow the vehicle. The regenerative brake system is a series system. A series system is one in which powertrain braking is used first, up to the limits of the powertrain torque capacity and battery capacity. After optimum regeneration is used, the friction brakes are applied to supplement braking demands. For information on regenerative braking, refer to Antilock Brakes / Traction Control Systems.

High-Voltage Bussed Electrical Center (BEC)

The high-voltage Bussed Electrical Center (BEC) acts as an interface between the high-voltage cables and the HVTB (High Voltage Traction Battery). The high-voltage BEC (Bussed Electrical Center) houses the 3 contactors (precharge, positive and negative) which, when commanded closed by the BECM (Battery Energy Control Module) , connect the HVTB (High Voltage Traction Battery) to various components for high-voltage consumption and/or charging of the HVTB (High Voltage Traction Battery). The high-voltage BEC (Bussed Electrical Center) design enables distribution of high-voltage to the high-current side (eCVT (Electronically Controlled Continuously Variable Transmission)) and low-current side (DC/DC (DC to DC Converter Control Module) and Air Conditioning Compressor Module (ACCM)). The low-current side is protected by a high-voltage/low-current 40A fuse. Any fault resulting in excessive current on the low-current side will open the fuse, but will not affect operation of the high-current side. The high-voltage BEC (Bussed Electrical Center) contains the contactors, the current sensor and the high-voltage/low-current 40 amp fuse.

The high-voltage BEC (Bussed Electrical Center) also interfaces with the BECM (Battery Energy Control Module) for monitoring of the high-voltage cable interlock circuit and control of the contactors. The high-voltage BEC (Bussed Electrical Center) also houses the current sensor which is monitored by the BPSM (Battery Pack Sensor Module). The current sensor is used to help determine the load or rate of charge of the HVTB (High Voltage Traction Battery) by sensing current flow into or out of the HVTB (High Voltage Traction Battery).

High-Voltage Cable Assembly

All cables that carry high voltage are integrated into one high-voltage cable assembly that runs between the DC/DC (DC to DC Converter Control Module) , the eCVT (Electronically Controlled Continuously Variable Transmission) , the ACCM (Air Conditioning Compressor Module) and the HVTB (High Voltage Traction Battery) (via the high-voltage BEC (Bussed Electrical Center)). Within the high-voltage cable assembly are 4 basic circuits:

- The high-voltage/high-current cables between the HVTB (High Voltage Traction Battery) and the eCVT (Electronically Controlled Continuously Variable Transmission).

- The high-voltage/low-current cables from the HVTB (High Voltage Traction Battery) to the DC/DC (DC to DC Converter Control Module) and the ACCM (Air Conditioning Compressor Module).

- The interlock circuit consists of small-gauge wiring wrapped around the high-voltage cables. The interlock circuit connectors are built in with the high-voltage cable connectors, and are either disconnected simultaneously with the high-voltage cable or must be disconnected before disconnecting the high-voltage cable, depending upon the type of connector being serviced.

- The LED and high-voltage AC wiring between the DC/AC inverter and AC power point. For information on the DC/AC inverter system, refer to Hybrid Drive Systems.

High Voltage Traction Battery (HVTB)

The HVTB (High Voltage Traction Battery) is a nominal 275 volts (actual operating range of 179-343 volts) DC energy source that receives high-voltage electrical power when required from the eCVT (Electronically Controlled Continuously Variable Transmission). The HVTB (High Voltage Traction Battery) also supplies high-voltage electrical power when required to the eCVT (Electronically Controlled Continuously Variable Transmission) , DC/DC (DC to DC Converter Control Module) and/or the ACCM (Air Conditioning Compressor Module).

The HVTB (High Voltage Traction Battery) system is connected to a floating ground system that keeps it isolated from the vehicle's 12-volt system. All charging and maintenance of the HVTB (High Voltage Traction Battery) is managed by the BECM (Battery Energy Control Module). Sensing of the HVTB (High Voltage Traction Battery) (battery state-of-charge, internal temperature, battery load) is done by the BPSM (Battery Pack Sensor Module).

HVTB (High Voltage Traction Battery) Service Disconnect Plug

The HVTB (High Voltage Traction Battery) uses a service disconnect plug which connects directly to the HVTB (High Voltage Traction Battery). The service disconnect plug has an internal circuit which includes a fuse. When the service disconnect plug is removed from the HVTB (High Voltage Traction Battery) , high voltage is no longer supplied to the high-voltage BEC (Bussed Electrical Center) , although there is still high voltage available on 2 circuits monitored by the BPSM (Battery Pack Sensor Module).

R-Mode Rebalance

Individual cells can deviate over the life of the HVTB (High Voltage Traction Battery). The purpose of the R-Mode Rebalance is to equalize the individual cell charges. By rebalancing the cells the HVTB (High Voltage Traction Battery) will maintain top efficiency. The rebalance process charges the battery pack to near a full state of charge and keeps each individual cell charge within a prescribed range of each other. The R-Mode Rebalance is sometimes run during vehicle operation as needed and is controlled by the BECM (Battery Energy Control Module). In some situations the BECM (Battery Energy Control Module) may not be able to properly adjust the cell levels on its own and a DTC may be set. The DTC would direct the technician to perform a service R-Mode Rebalance. This is done with the use of a scan tool by following the directions within the service function.

Vehicle Shut Down

A vehicle shut down signal is sent when the battery 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, interlock circuit failure, etc.). When vehicle shut down occurs, the Stop Safely warning indicator will be illuminated warning that the vehicle will be shut down within a matter of seconds and that the operator should pull off the road as soon as possible. Depending on the fault condition that lead to the shut down, the vehicle may or may not re-start if the condition has corrected itself. If the fault condition is severe enough, the fault will have to be repaired and DTCs cleared before the vehicle will re-start.