are bolted to the power control module to ensure a good
electrical connection.
A battery pack cover encloses the modules and pro-
tects them from damage. It also protects people from
electric shock. Battery pack cover(s) are held on with
machine screws. Some hybrids have the power control
module and battery pack housed together.
Warning!
Never remove a cover from a hybrid battery
pack. The manufacturer’s warranty may become
void if the cover is removed. Additionally, if
you touch a battery pack cable with your bare
hands, you can be electrocuted!
Battery pack temperature sensors are used to protect
against heat damage. A tremendous amount of current
flows in and out of the battery pack when the battery is
being recharged and when it is powering the motor-gener-
ator(s). If a battery pack temperature sensor detects cell
overheating, it will signal the hybrid ECU to disconnect the
power control module, preventing further overheating.
If a battery problem exists (extended battery service
life, impact damage from a collision, hit from lightning,
short in cell, etc.), the ECU will instantly shut the electric
drive system down and trigger a malfunction indicator
light in the dash.
Motor-Generator
A hybrid motor-generator functions as both a pow-
erful traction motor and as a high-energy alternator in the
vehicle’s power train. The hybrid motor-generator(s) has
several functions:
• Helps power the drive train and propel the vehicle.
• Recharges the HV battery pack.
• Cranks the internal combustion engine.
• Ηelps slow and stop the vehicle.
The basic parts of a motor-generator include the
armature, stator, and housing. The armature consists of a
set of permanent magnets mounted inside a segmented
steel disc. See Figure 38-7A. The stator is a set of sta-
700 Section 5 Electrical Systems
Figure 38-7. Study this simplified drawing of a hybrid motor-generator assembly. A—The armature is a steel ring with permanent
magnets imbedded in its outer diameter. B—The stator is made up of coils consisting of sets of windings wrapped around iron cores.
C—The motor-generator housing holds the stator coils stationary. D—When assembled, the armature and stator form an assembly
that can function as a high-torque motor or a high-energy generator.
Permanent
magnets
A
C
B
D
Armature
Motor-generator
housing
Stator
Coil windings
Iron cores
Armature spins
inside stator