routed through the hybrid drive components to carry heat
back to the radiator for transfer into the atmosphere. The
hybrid often has two radiators: the conventional engine
radiator and the hybrid drive radiator.
Hybrid air cooling circulates outside air through the
battery pack enclosure and then forces this air out of the
vehicle. The air carries away heat and vents electrolyte
gases away from the vehicle. Forced battery pack venti-
lation is often provided by an electric blower motor that
directs outside air through the battery pack enclosure.
See Figure 38-20. The 12-volt blower motor is similar
to that used in a passenger-compartment climate control
708 Section 5 Electrical Systems
Figure 38-19. This hybrid drive uses an extra radiator to remove excess heat from the hybrid drive system. Keeping hybrid compo-
nents cool increases electric power transmission efficiency and protects them from thermal damage. (Toyota)
Engine
radiator
Hybrid drive
radiator
Reservoir
tank
Power control
module
Water
filler
Hybrid
transmission
Electric
water pump
Figure 38-20. Air cooling is used to remove heat from the battery pack. A blower pulls air from 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
A - A Cross Section