JEC COMPOSITES MAGAZINE - Issue #98 - July/August 2015 - 28

additive

and dirt. The housing needs to be electrically isolating to avoid short outs in the
battery and powertrain. It should be noted
that battery efficiency is increased when
temperature is managed well throughout
the charging and discharging processes.

Fig. 10: Critical areas for heat management in
vehicles

Fig. 11: Battery housing of an electric car

Fig. 12: Charging unit of an electric car

Fig. 13: Schematic drawing of a fuel cell pack
(©Wikipedia)

For applications such as housings for batteries, electronic parts or catalyst protection in a vehicle, good thermal management helps to take heat away from critical
areas. The battery pack in an electricpowered or hybrid car is often located
between the passenger cabin and the floor,
as shown in Figure 11.
Lead batteries that are used in most
gasoline and diesel cars today do not have
the same thermal management challenges
as high efficiency nickel-metal hydride
(NiMH) batteries. The charging of these
NiMH power packs is done via the braking
system and the momentum when driving
force is not required, therefore they get
quite hot during the movement of the
vehicle, as they are permanently charged
and discharged. In some electric cars and
many city buses, a separate engine supplies
electrical power to these cells.
The charging unit in a vehicle also carries
a heat load when in use. This is another
area where BN-filled composites can help
to manage the temperature peak so that
there is no danger for the user. Figure 12
shows such a charging unit.
Interest in fuel cell technology will grow
as the desire for minimizing CO2 emissions from cars grows. A fuel cell needs a
housing that is water resistant, electrically
isolating and will manage the heat inside
from the reaction of hydrogen (H2) and
oxygen (O2) into water at the membrane.
Also, the efficiency of the fuel cell is determined by thermal management. The same
temperature must be maintained throughout the cell in order to prevent destruction
of the cell through thermal loading. This
is particularly challenging since the 2H2 +
O2 -> 2H2O reaction is highly exothermic,
therefore a large quantity of heat is generated within the fuel cell. See Figure 13 for

28 jec composites magazine / No98 July - August 2015

Fig. 14: Li-ion battery

a detailed description of a fuel cell.
The next generation of rechargeable batteries will be lithium (Li) ion, which also
requires good heat management. These
will not only be used in vehicles, they are
already commonly used in computers,
cameras and measuring devices. To protect
the battery and the device, good thermal
management is a must. Figure 14 shows a
modern lithium-ion battery pack.

Thermal management
Another critical area of thermal management in the car is the headlamp. While the
reflectors are mostly injection moulded
from bulk moulding compound (BMC)
or thermoplastics, the housing of the headlamp has to manage the heat from standard
halogen or xenon bulbs. Due to its thermal
stability, BMC is typically chosen for the
reflector, whereas the housing behind the
reflector is often moulded from fibre-reinforced polypropylene (see Figure 15).
When LED headlamps start widely
replacing the technologies in use today,
this will increase the need for excellent heat management, not only for the
reflector but also for the housing. LED
lamps are very sensitive to heat - the
higher the temperature, the less effective
the LED chips are. To show a practical

Fig. 15: Headlamp with reflector and window

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #98 - July/August 2015