RV FEATURE
:
LITHIUM
SAFETY FIRST
IN PART THREE OF OUR SIX-PART SERIES
ON LITHIUM, WE LOOK AT THE INHERENT
SAFETY FEATURES OF LIFEPO4 BATTERIES .
LITHIUM BATTERIES
PART 3
Lithium batteries are used in a range of products,
in everything from mobiles phones to toys to
electric vehicles. The next is a pouch-style battery, used in
mobile phones. These are susceptible to heat
and humidity.
A range of different types of lithium batteries
is used across this spectrum of devices. The
difference is the composition of the internal
chemistry. Lithium batteries can be constructed
differently using a range of lithium polymer
chemistries, such as manganese, cobalt, nickel
and aluminium. The final style is the prismatic cell used inside
LiFEPO4 batteries. These cells are made in strong
aluminium cases and at a voltage such that when
combined together form the perfect replacement
for 12V in lead acid.
Lithium iron phosphate (LiFEPO4) is best suited
to RVs, where lithium batteries are designed
to replicate the properties of a deep-cycle lead
acid battery.
It is the safest of all the chemistries as it has a
high ‘thermal runaway point’, which is
substantially higher (>80C) than other
chemistries. Thermal runaway is where the
temperature rises rapidly (within milliseconds),
causing the energy contained within the battery
to be released suddenly in an unstoppable
chain reaction.
Across the top of these cells is a battery
management system that controls the voltage
and amps of the cells individually and jointly, and
has a range of protection mechanisms, such as
over voltage, under or over charging, thermal and
short circuit. The BMS performs a critical function
in the overall performance and safety of LiFEPO4
batteries.
Unlike a lead acid battery, a lithium battery has no
need for vents — no toxic gases can escape if it
malfunctions.
The oxygen atom in a LiFEPO4 battery is extremely
tightly bonded such that even if the battery is
abused, it will not release oxygen, which means
there is nothing to burn. There are no specific enforced regulations in
Australia regarding batteries; however, while
most batteries will be certified at least to cell
level, BMPRO Sentry batteries are certified
additionally as a complete battery, with all cells
and BMS together, adding an additional level of
compliance and level of safety.
There are a range of cell constructions, such as
cylindrical batteries, shaped liked AA batteries.
These are low in capacity and used widely in
electric vehicles. These are the only lead acid replacement LiFEPO4
batteries that I am aware of that undergo continual
testing in Australia (which is done at BMPRO
headquarters).
– David Bayliss, BMPRO ambassador
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