THE EDGE
As lithium batteries are widely used
in sectors such as electric vehicles,
industrial energy storage and terminal
devices, and the industry ecosystem is
established, the cost of lithium batteries
decreases year by year. However, the
cost of lead-acid batteries is fluctuating
and will rise in the future. Therefore,
lithium batteries will have obvious cost
advantages in the near future and will
see wider application in data centres. As
different lead-acid battery brands and
prices exist in the market, lithium batteries
are currently more expensive than leadacid
batteries.
Safety assurance for lithium
battery application in data centres
1. Root causes of lithium battery
safety incidents
If battery over temperature and
overvoltage occur, many side reactions
of heat release occur inside the battery,
causing positive feedback of heat.
Consequently, thermal runaway occurs,
which will generate a high temperature
and a large amount of flammable gas and
can even cause a fire. The root causes
of thermal runaway lie in mechanical,
electrical and thermal stimulation.
2. Lithium battery safeguarding methods
Lithium-ion battery burning incidents in
recent years are caused by internal short
circuits, lithium plating, high temperature
and volume change.
LFP cells alone cannot solve all the
problems. Lithium battery designs in
dimensions such as cell, pack, BMS,
system and cloud computing/Big Data
should be combined to minimise burning
incidents due to thermal runaway.
(1) Cell material selection: LFP is
preferred as its safety is ensured thanks
to a high temperature for thermal runaway
and a low rate and amount of heat yield.
(2) Cell structure safety design: The
mechanical structure is cut off promptly
to suppress temperature rise and the
coating inhibits thermal runaway.
• Mechanical structure: Components
such as the fuse and overcharge
safety device (OSD) are promptly
cut off in case of a short circuit and
overcharge to suppress temperature
rise and prevent thermal runaway
due to chain reactions.
• Functional coating (chemical
protection): If an internal short circuit
occurs and the mechanical structure
does not work, the functional coating
suppresses the shrinkage of the
isolation film to avoid large-scale
short circuits.
(3) Battery pack safety design: Two-level
design in four dimensions ensures battery
pack safety. Examples:
• Laser soldering eliminates the risk of
loosening screws
• Multiple temperature sensors monitor
the internal temperature and voltage
in real time
• Proper clamping ensures structural
stability
• The insulating protection plate
safeguards positive and negative
terminals
• The plastic insulating bracket ensures
insulation and structural strength
between cells
• The insulation film on the cell surface
insulates the cell from external
components
LITHIUM
BATTERIES
WILL HAVE
OBVIOUS COST
ADVANTAGES
IN THE NEAR
FUTURE AND
WILL SEE WIDER
APPLICATION IN
DATA CENTRES.
(4) BMS safety design: The three-level
BMS architecture, with voltage, current
and temperature sampling, equalisation,
threshold alarm protection, internal shortcircuit
detection algorithm and algorithms
for internal temperature estimation and
lithium plating, ensure that cells will not
cause thermal runaway.
(5) System safety design:
• The intelligent battery control system
controls the voltage, current and
power of each battery to avoid bias
current and cross current.
• The cabinet-level fire extinguishing
system quickly suppresses thermal
runaway for precise, efficient and
eco-friendly protection.
(6) AI safety assurance: Key data is
uploaded to the cloud for monitoring the
battery status in real time. Horizontal and
vertical comparison, database and safety
algorithm analysis collaborate to provide
monthly and daily safety warnings.
Conclusion
Compared with lead-acid batteries, lithium
batteries have inherent advantages such
as low requirements on load-bearing
capacity, small footprint, high energy
density and long cycle life. Lithium
batteries will be widely used in data
centres when the cost is further reduced.
To ensure the safety of lithium batteries,
LFP cells are recommended and the
designs in dimensions such as pack, BMS,
and system need to combine. Huawei
SmartLi UPS is such solution with safest
LFP cell that can pass several reliability
tests and have already large-scale used
in different industries. ◊
70 Issue 18
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