here. - Auto Electronics Magazine

C O V E R S T O R Y
HYBRID VEHICLES PROPEL INCREASED ELECTRONICS CONTENT
THE ELECTRONIC
GAS TANK
The hybrid vehicle needs
energy storage for the
electric portion of its
propulsion system in addition to
the gasoline or diesel fuel tank
for the engine. Long term this
could come from fuel cells, but
today batteries provide the energy
storage. The 12 V battery has gone
through various improvements
during its 50-some years as the
reigning vehicle electrical system
voltage. However, the electrical
propulsion in the hybrid requires
storage capability beyond
traditional 12 V battery technology.
Battery chemistries that are
being evaluated and developed
for hybrid vehicles include
valve-regulated lead acid
(VRLA) batteries, nickel metal
hydride (NiMH) and Lithium
ion (Li-ion) technologies. Key
concerns with these batteries in
hybrid applications are cost and
reliability. As shown in the spider
chart, VRLA technology excels
in economics, cold cranking and
recycling infrastructure because
it is an improvement on the
established lead-acid battery. In
contrast, Li-Ion technology has
the highest energy density while
NiMH has the highest specifi c
power and charge acceptance.
Today, 42 V vehicles such as
Toyota’s Crown and GM’s Silverado
22 WARD’S AUTO ELECTRONICS | OCTOBER 2004
and Sierra models use VRLA technology. Higher-voltage vehicles such as
the Toyota Prius and Ford Hybrid Escape models use Ni-MH batteries.
In Ford’s Hybrid Escape, the Sanyo battery also includes battery control
electronics.
Toyota reduced the battery voltage from 275 V in its initial Prius to
202 V for the new Prius and used a dc-dc converter to boost the voltage to
500 V. With 500 V, they use a 50 kW traction motor instead of 33 kW motor
used with power direct from the 275 V battery. The voltage conversion
A comparison of key battery characteristics for valve regulated lead acid (VRLA)
versus NiMH versus Li-Ion [8]. Background: Sanyo’s 330V sealed NiMH in the Ford
Escape has 250 D size cells in series.
M O R E