Inrush Current Control Technology Boosts Power Converter Reliability

[ 22 ] COTS Journal November 2011
Untitled-4 1 7/25/11 10:31:05 AM
Special Feature
Figure 2
Large-format Lithium-ion prismatic cells are proving themselves in interesting pilot
programs as they offer up to 70 times the capacity of traditional packaged lithium batteries
that are the size of a D cell.
cost of lead-acid batteries has made them
a popular choice for several years, many
integrators are now turning to advanced
chemistries such as Lithium-ion for more
energy-dense applications. Figure 1 lists
the many advantages Lithium-ion batteries
have over lead-acid batteries.
Finding the Right Fit
Large-format cells, also referred to
as HyperClass Lithium-ion prismatic
cells, (Figure 1) on the market today are
proving themselves in interesting pilot
programs as they offer up to 70 times
the capacity of traditional packaged
lithium batteries that are the size of a D
cell. While most lithium batteries are
produced as small cylindrical cells up to
3 Ah or “pouch” prismatic cells up to 10
Ah, large-format cells can range from 50
Ah to 200 Ah. With each individual cell
being considerably larger, large-format
batteries greatly decrease the number of
cells needed within the battery module,
which improves reliability and efficiency
while lowering maintenance costs and
the number of connectors. Individual cell
monitoring with the use of Battery Management
Systems (BMS) is a key to success
with these systems.
Weight, temperature and energy requirements
are all important factors to
consider when choosing Lithium-ion bat-
teries. Some have very wide temperature
ranges and can be ideal for in-field vehicles
that experience high desert temperatures
and meet longer runtime demands, but
not many have military testing certification,
which is an important requirement.
Lithium iron phosphate chemistry—a
form of Lithium-ion—is by far the safest
and therefore the best choice for power
delivery applications.
Energy Storage: The Silent
Advantage
The Tank Automotive Research,
Development and Engineering Center
(TARDEC), has developed a hybrid energy
storage system suited for tanks and
Stryker armored vehicles. This energy
storage system has been implemented
within the current Silent Watch program,
aimed at allowing military vehicles
to operate with little to no audible
signature. Developing tanks and military
Humvees more suited for covert missions
is a major challenge, and energy storage
plays a huge role in the development of
this program.
The Silent Watch vehicles rely on
the battery system to operate quietly for
stealth and tactical missions (Figure 2).
With the communications systems being
powered by the battery, the audible signature
of these vehicles is greatly reduced