Bolt EV Propulsion System

The propulsion of the Bolt EV (Fig. 5) is achieved by an electric drive transmission that transfers the energy from the high voltage battery pack to the front drive wheels.


2017 Chevrolet Bolt EV

Fig. 5


Drive Motor Battery System


The high voltage battery is designed to last for the life of the car and is covered by an 8-year/100,000-mile (160,000 km) warranty. The high voltage battery assembly is removed and installed from underneath the vehicle. The battery pack is protected by a lightweight steel frame integrated into the body structure.


The Battery Energy Control Module, a current sensor, and the high voltage contactors are located within the hybrid/EV battery assembly. The Hybrid/EV Powertrain Control Module 2 is mounted within the passenger compartment, beneath the right front seat.


Battery Construction


The hybrid/EV high voltage battery weighs approximately 946 lbs. (429 kg) and contains 288 individual nickel-lithium-ion cells. (Fig. 6) Three cells are welded together in parallel in a cell group. There are a total of 96 cell groups in the hybrid/EV battery assembly that are electrically connected in series. Each individual cell group is rated at 3.5 volts, for a nominal system voltage of 344 volts of direct current (DC).


2017 Chevrolet Bolt EV battery system

Fig. 6


Because the high voltage battery was engineered specifically for the Bolt’s arduous duty cycle, the 288 prismatic cells have greater nickel content and, therefore, will run slightly warmer than those in the Chevrolet Volt or the Chevrolet Spark EV.


The hybrid/EV battery pack contains a total of 6 battery temperature sensors mounted to certain battery cell modules. The hybrid/EV battery pack also contains a coolant inlet temperature sensor.


Located within the high voltage hybrid/EV battery pack is the K16 Battery Energy Control Module which monitors the temperature, current and voltage of the 96 battery cell groups. The voltage sense lines are attached to each individual cell group.


Diagnostics and system status are communicated from the Battery Energy Control Module to the K114B Hybrid/EV Powertrain Control Module 2


The battery pack will be serviceable by certified GM dealerships when necessary. Some of the battery pack’s accessory components are located under the hood for easier access.


TIP: The hybrid/EV high voltage battery will be on TAC Restriction and Exchange during the vehicle launch period. Batteries will be distributed by an Electronic Service Center.


System Components


The Hybrid/EV high voltage battery assembly consists of the following components. (Fig. 7)


F07 Bolt EV components

Fig. 7

1. K10 Coolant Heater Control Module.
Service Part Name: Heater Coolant Heater.

2. T6 Power Inverter Module.
Service Part Name: Drive Motor Power Inverter Module.

3. Hybrid/EV Battery Assembly.
Service Part Name: High Voltage Battery.

4. S15 Manual Service Disconnect.
Service Part Name: Drive Motor Battery High Voltage Manual Disconnect Lever.

5. E54 Hybrid/EV Battery Pack Coolant Heater.
Service Part Name: High Voltage Battery Heater.

6. G1 A/C Compressor.
Service Part Name: Air Conditioning and Drive Motor Battery Cooling Compressor.

7. T18 Battery Charger.
Service Part Name: Drive Motor Battery Charger.

8. K1 14V Power Module.
Service Part Name: Accessory DC Power Control Module.

9. T24 Battery Charger-DC.
Service Part Name: High Voltage Battery Disconnect Control Module Assembly.


Electric Drive Transmission


The electronically-controlled, fully automatic transmission consists primarily of a 150kW drive motor, a differential/offset gear set, a high voltage electric auxiliary transmission fluid pump and housing, and two axles. (Fig. 8)


2017 Chevrolet Bolt EV drive unit

Fig. 8


The differential/offset gear set provides the fixed forward and reverse ratio. Changing speed and torque is fully automatic and is accomplished through the use of a drive motor generator power inverter control module located under the hood. The drive motor generator power inverter control module receives and monitors various electronic sensor inputs and uses this information to vary the torque output to the drive axles based on throttle position.


The lubrication system uses an electric auxiliary fluid pump motor assembly located outside of the transmission for lubrication of rotating components. The transmission fluid pump operates under low pressure and will only run when out of Park or Neutral and vehicle speed is detected.


Gear position is selected using the Electronic Precision Shift (EPS) system, which is also used on the new Buick LaCrosse and Cadillac XT5. The shift-by-wire systems sends electronic signals to the drive unit to select the drive mode. The selected gear position illuminates in red on top of the shift lever. After shifting, the lever returns to the center position.


TIP: The transmission will not stay in Neutral for an extended period. It will automatically shift into Park.


– Thanks to Sherman Dixon and Chuck Wieseckel



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