Battery System, Hybrid Drive: Description and Operation

Plug-In Charging System Description and Operation

Plug-In Charging System components

The Chevrolet Volt high voltage battery charging system consists of four main components: The electric vehicle supply equipment (EVSE, or cord set), the vehicle charge port (including receptacle), the battery charger, and the hybrid battery pack. A variety of mechanical, visual and audio indicators / devices are used to communicate / interface with the customer or other user of the charging equipment.

Electrical Vehicle Supply Equipment

The 120 V cord set provided with the vehicle is referred to as "Portable EVSE". This device features a standard U.S. type 120 V plug on one end and an SAE compliant plug designed to interface with the vehicle charge port receptacle on the other end. The cord set features a charge current interrupt device with AC power, fault and missing ground indicators, and it is stored beneath the vehicle's load floor. An optional 240 V cord set, or "Fixed EVSE" is also available to customers who want to reduce the amount of time needed to recharge the high voltage battery. The 240 V cord set is referred to as "fixed", because it is hard-wired to a 240 V power supply and mounted to the wall in the customer's garage. The 240 V cord set features the same SAE compliant plug on the vehicle end as the 120 V device.

The Electrical Vehicle Supply Equipment Indicators and the Vehicle Indicators

The electrical vehicle supply equipment has three indicators on it. The AC present indicator becomes solid lit green when AC voltage is present at the wall plug. The Fault Indicator becomes solid lit red for a current trip or failed self check. The Missing Ground Indicator becomes solid lit red when no ground is detected at the wall outlet.

The charging system is supervised and controlled by the hybrid powertrain control module 2. The hybrid powertrain control module 2 is a primary OBD controller, and all diagnostic trouble codes will set in that module (even though some of the diagnostics are actually run within the battery charger). Charging events can be delayed at customer request to take advantage of lower rates during non-peak hours. The status of charging events (including delays) is communicated to the user through visual indications (instrument panel mounted charge status indicator or CSI ) and audio tones (charge status enunciator or CSE). The vehicle charge status indicator, located on the top middle of the instrument panel, will be solid lit green the vehicle is charging under automatic control. It will have a fast flash green if the charging is delayed and will begin later. It will have a slow flash green when charging is complete. A solid lit yellow indicator means the vehicle is not able to accept a charge. And if there is no indicator lit it means the electronic vehicle supply equipment is not working properly or connected.

Vehicle Receptacle

The vehicle receptacle is located behind a door on the charge port (driver's side front fender). The receptacle is accessed by depressing a switch located on the inside of the driver's door. Charge port illumination is used to display the status of the vehicle content theft deterrent system as well as for customer convenience. When the cord set plug and receptacle are joined, the resulting configuration is referred to as a "coupler".

Battery Charger

The hybrid battery charger is a serviceable assembly containing several micro-processors, two separate high voltage chargers and a single low voltage charger. It is mounted behind the passenger's side headlamp assembly and is flash programmable, communicating on both GMLAN and the High Voltage Energy Management Expansion bus. Engine coolant (DexCool) is used as a cooling medium to ensure that the charger does not exceed its maximum designed operating temperature. The low voltage charger is used to ensure that the 12 V battery does not become depleted during a charge event, while one the high voltage chargers is used with a 120 V charge source and both are used with a 240 V charge source.

Hybrid Battery Pack

The hybrid battery pack is a liquid cooled, "T" shaped lithium-ion energy storage system located beneath the vehicle. The 360 V direct current battery is formed from 288 cells which are grouped together to form distinct blocks, referred to as sections. The battery is connected to the propulsion circuit or charging circuit using unique pairs of contactors. Both circuits cannot be "live" at the same time. In general terms, the main contactors will close when the ignition switch is in the "on" position. Charging events cannot be initiated when the main contactors are closed. The high voltage battery is also connected to two distinct low voltage "high voltage interlock circuits", one for propulsion, and one for charging. As with the contactors, the two HVIL circuits cannot be energized at the same time. The high voltage DC output from hybrid/drive motor battery charger is delivered to the high voltage battery through an HVIL protected connector at the front of the battery bulkhead/battery disconnect unit (BBDU). The charger fuse is also serviceable through an HVIL protected access cover on the BBDU.