Truck & Off-Highway Engineering - June 2021 - 14

EXECUTIVE VIEWPOINTS
Batteries go underground
A Saft expert evaluates various Li-ion chemistries and strategies - battery
swapping vs. fast charging - for electric mining vehicles.
by Xavier Iraçabal
An underground mining BEV is a relatively unusual application
for onboard Li-ion battery systems, with demanding usage
patterns requiring total reliability for five years, even when
subjected to extreme charge/discharge cycling.
D
iesel-powered mining vehicles add risk and
complexity underground. Operators need
extensive ventilation infrastructure to manage
the exhaust gases, and this becomes
exponentially larger as mines go
deeper. That can be significant in
terms of cost and space for today's
deepest mines, which reach depths of
4 km (2.5 miles).
Around 80% of the energy demand
for underground mining is associated
with load, haul and dump (LHD) machines
and other vehicles that transport
people, equipment and materials.
Diesel engines are a source of
CO2
and particle emissions, so
switching to battery power is an opportunity
to decarbonize and improve
air quality underground.
Despite these advantages, operators
have held back from electrifying
vehicles because of past limitations
on battery technology. However, today's
lithium-ion (Li-ion) battery
technology has matured to the point
where it is economically viable and
reliable.
14 June 2021
Battery swapping or fast charging?
What operators want is total reliability from vehicles during five
years of heavy use in the toughest environments. Batteries need
to deliver high power over shifts of around four
hours. They also need to support frequent charge
and discharge cycling, 24-hour operation and high
ambient temperatures.
Two schools of thought have emerged as solutions
Xavier Iraçabal, Saft mobility
product manager.
" Li-ion battery
technology has
matured to the
point where it is
economically viable
and reliable. "
to deliver this: battery-swapping and fast-charging.
Battery-swapping calls for two identical sets of batteries,
with one installed and powering the vehicle
and the other charging. At the end of a four-hour
period, the vehicle will pull up to a swap-and-charge
station, where the battery will be swapped out for
the fresh battery. This normally takes 15 minutes or
so while the driver has a break.
This strategy uses slow charging that doesn't place
a significant burden on the mine's existing electrical
infrastructure. However, the battery changeover adds
an additional task for the underground team and requires
lifting equipment for safe handling.
The other approach uses fast-charging batteries
that are permanently fitted into the body of the
vehicle. The latest Li-ion electrochemistry is amenable
to fast charging within around 10 minutes
during breaks and shift changeovers, as well as
TRUCK & OFF-HIGHWAY ENGINEERING
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Truck & Off-Highway Engineering - June 2021

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