Chapter 22 Hybrid Drive Systems 437
Figure 22-29. Air cooling is used to remove heat from the battery pack. A fan pulls air through the passenger compartment, routes
the air over the battery pack, and then forces the heated air to the outside of the vehicle.
Blower
Motor
Airflow
To Outside
Battery Pack
Air Inlet
Battery Pack
Housing
Battery Pack
Modules
Cross Section
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A split drive hybrid has the internal combustion
engine crankshaft rotate one drive axle and the motor-
generator rotate another drive axle.
❑
A full hybrid uses all electric energy to initially accel-
erate and propel the vehicle; the internal combustion
engine only runs when the HV battery pack becomes
almost fully discharged.
❑
An assist hybrid uses a small motor-generator to assist
the gas engine in accelerating and propelling the
vehicle from a standstill to about 10 to 20 mph.
❑
Home wall outlet power is used to recharge the HV battery
pack of a plug-in hybrid if the hybrid has not used regen-
erative braking to fully recharge the HV battery pack.
❑
The hybrid battery pack consists of several sealed NiMH
(nickel metal hydride) or Li-Ion (lithium-ion) battery modules
wired in series to produce a high-voltage power source.
❑
A motor-generator helps to power the drive train and
propel the vehicle, recharge the hybrid battery pack,
crank the internal combustion engine, and slow and
stop the vehicle.
❑
A single motor-generator hybrid uses only one large
motor-generator to assist the gas engine; a dual motor-
generator hybrid uses two separate motor-generators
located at different locations in the drive train; and
a triple motor-generator hybrid typically uses two
motor-generators in the transmission or transaxle and
the other in the rear drive axle assembly.
❑
A hybrid power control module is a set of electronic
circuits for altering and feeding current between the HV
battery pack and motor-generator; it contains an inverter
circuit, a converter circuit, and a motor-generator ECU.
❑
A hybrid power splitter is a planetary gearset used to control
the engagement of the motor-generators with the transaxle
or transmission output gears, chains, belts, and shafts.
❑
Hybrids operate off of two separate electrical systems: a
conventional 12-volt battery and a hybrid battery pack.
❑
Three methods used to cool a hybrid vehicle are
hybrid water cooling, hybrid air cooling, and hybrid
refrigerant cooling.
Review Questions—Chapter 22
Please do not write in this text. Place your answers on a
separate sheet of paper.
1. List the six major assemblies found in a gas-electric
hybrid drive system.
2. Explain the difference between a full hybrid and an
assist hybrid.
3. In a(n) _____ hybrid, the internal combustion engine
has no mechanical connection to the drive train.
4. A(n) _____ hybrid can be connected to a 120-volt AC
home wall outlet and extension cord to fully recharge
the HV battery pack at night.
5. List the six modes of hybrid operation.
6. Hybrid battery packs contain several battery modules
wired in _____ to produce a high voltage.
7. A hybrid high-voltage system typically operates on
voltages that range from _____ to _____ volts.