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Batteries with a boost
Today’s cars are equipped
with a lead-acid accumulator
as an electrical energy storage
device. It is not uncommon in luxury
vehicles to find two batteries. The
requirements for the accumulator,
namely starter operation and supply
of the on-board electronics, are
extremely di erent. First of all, very
high currents must be provided at
short notice in starter operation, and
also at very low temperatures and
also to operate the on-board
electronics, charge is continuously
removed from the battery over
longer periods of time.
To meet both requirements in
vehicles equipped with a single
battery, it must be clearly oversized,
as the starter function is critical.
Another reason for the oversizing
of lead accumulators used today is
that the service life of lead-acid
accumulators is highly dependent
on the depth of discharge. The
higher the depth of discharge under
operating conditions, the shorter
the battery life. An oversized
accumulator reduces the depth
of discharge and thus extends the
battery life.
To decrease the size and weight
used by the battery for starter
operation, Fraunhofer ISIT has
developed a modular accumulator
system, consisting of an extremely
robust high-power battery named
Li-Booster, which combines the
benefits of highly responsive and
power e icient power electronics.
The objective was to select
appropriate materials and develop
a manufacturing process that
ensures a long lifetime and safety,
while providing the potential for a
very good load capability.
Electrochemical energy storage
devices with lithium titanate as the
anode material and lithium
manganese oxide as the cathode
material comply with these
requirements. For the
lithium-booster, a
separator,
developed by
Fraunhofer ISIT,
was also used.
The result was
a 3.3Ah cell that
can be
discharged
with 200A
over a short
period of time.
In the
lithium-booster
every one of the
12 high-power
cells are
connected to
form a battery
module. The whole
system is set up
depending on the
application of a
variable number of
these modules.
202 // July 2019 // www.electrichybridvehicletechnology.com
Fraunhofer
ISIT’s battery
management
system
ensures that
the charge
states of the
individual cells
do not
gradually drift
apart during
operation. It
includes active
balancing, to
distribute excess
energy of a single
cell to other cells
within the same
module. Di erent
states of charge of the
individual modules are
balanced very fast and
with low-loss. In addition,
the high-voltage battery is
fully de-energized when the
electronics are switched o ,
reducing electrical hazards in case
of accidents.
The compact size of the
Fraunhofer ISIT booster charging
technology enables discharging up
to 140°F (60°C) and can be charged
up to 68°F (20°C), while also
possible below 14°F (-10°C). These
parameters qualify the Li-Booster
module for starter applications in
the automotive, aircraft and marine
industry. For numerous applications
where both high current burst and
long-term energy delivery are
required, the small size of the
module makes it the ideal addition
to a deep-cycle lead-acid battery.
Developments in lithium-based accumulator technology are
providing increased power for EVs in a compact and durable frame
To decrease the size and weight used
by the battery for starter operation
Fraunhofer ISIT has developed
a modular accumulator system,
consisting of an extremely robust
high-power battery named Li-Booster
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