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High-performance and safety: Torqeedo LIMA
cells
Lithium-based battery
systems are by far the most powerful energy carriers currently available. On
the one hand they are characterized by a high specific energy density. This
means that they are able to store a large amount of energy per kilogram of
battery weight. In addition, lithium batteries can withstand high current:
in other words, they are able to deliver their capacity even under high
loads. Both of these characteristics are of great importance for
applications in boat drives: on the one hand, the battery weight and volume
on board is reduced.
On the other hand, the lithium-based battery systems ensure that the power
supply does not collapse even when the boat‘s electro-motors
temporarily draw high currents from the batteries.
An additional advantage: lithium batteries do not display a memory effect
and are cyclically stable. Even when stored for many months, almost no
charge is lost, in contrast to conventional lead batteries.
Torqeedo batteries are also extremely robust and are secured against
incorrect handling. In addition, they are protected against
short-circuiting, overvoltage and excessive discharge.
The high energy density of lithium cells demands effective safety technology.
For this reason, Torqeedo uses exclusively lithiummanganese safety cells.
These so-called LIMA cells offer the highest safety standard of all lithium-based
batteries: Only LIMA cells are able to master the necessary safety tests
even when the safety electronics are switched off. These safety tests
include in particular:
• Crash tests: a fully-charged battery is crushed with a ten-ton hydraulic
press
• Nail tests: a nail is hammered right through the case of a charged battery
until it comes out of the other side. This leads to the maximum possible
number of battery cells being short-circuited.
• Overcharge tests: the battery packs are overcharged with 42 V at 7.5 A
until the cells are destroyed.
• Short-circuit tests: the main contacts are short-circuited without the
safety circuit.
• High-temperature tests: the aforementioned
tests are undertaken on a 150° C pre-heated battery.
Alternative lithium battery
concepts in round cell format or in lithium polymer packs (“Li poly”) do not
fulfill these criteria due to the chemical composition of the battery
(cobalt or nickel cathode). Additionally, in case of a fault such as, e.g.
shortcircuit, overload, mechanical damage, lithium polymer packs react in a
highly critical manner due to the missing safety mechanisms immanent within
the cells.
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legal mentions - Copyright
Jean-Pierre Masquelier
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