Truck & Off-Highway Engineering - June 2021 - 16

EXECUTIVE VIEWPOINTS
A fixed LTO battery rated at
800 V with 250-Ah capacity
would deliver 3 hours of
operation with a 15-minute
break for fast charging.
Inside the modules, Saft is using cells that are prismatic
in shape, rather than the traditional cylindrical
shape. Because prismatic cells are rectangular in cross
section, there are no gaps between cells, allowing
maximum energy density and battery performance to
be packed into the available space.
The battery system also can be complemented with
components such as a heavy-duty enclosure, thermal
management system or fire suppression system, depending
on the OEMs needs. In addition, operators
can monitor the performance of the battery systems
across their entire fleet of vehicles.
Evaluating LHD scenarios
As a practical comparison, Saft evaluated two alternative
scenarios for an underground LHD vehicle using
swappable and fast-charging batteries. In both cases, a
LHD machine was considered that weighs 45 tons unladen
and 60 tons fully loaded with 6-8 m3
of material.
The evaluation also envisaged vehicles with batteries of
similar weight and volume of 3.5 tons and 4 m3
in an
envelope measuring 2 m x 2 m x 1 m. This enables a
like-for-like comparison of the two approaches.
For battery swapping, the battery system was
based on NMC or LFP chemistry. It would support sixhour
shifts for the LHD vehicle from a battery rated at
650 V and with 400-Ah capacity. When swapped off
the vehicle, they would require three-hour charging.
They would deliver 2,500 cycles over a calendar life of
3 to 5 years.
When applied to fast charging, a fixed LTO battery of
the same size and weight would be rated at 800 V with
250-Ah capacity. It would deliver 3 hours of operation
16 June 2021
NMC and LFP are
the most commonly
used chemistries in
underground mining
vehicles, particularly
for slow charging with
batteries swapped
between shifts.
with a 15-minute break for charging. The LTO battery would last
20,000 cycles, giving it a calendar life of 5 to 7 years.
While these scenarios provide an interesting comparison, a realworld
vehicle designer can apply the modular approach to develop a
battery system that will precisely suit the preferences of their customers
and the needs of individual vehicles. For example, they could extend
the duration of the shift by increasing the size of the batteries.
Ultimately, mine operators will choose the vehicles that are best
suited to the configuration of their mines. That will require a fine balance
to consider the available space underground, as well as the accessibility
of high-power electricity. The TCO of the vehicles and the
infrastructure needed to support them also will influence decisions.
That's why it's important for battery companies to provide vehicle
designers with flexibility.
Xavier Iraçabal, mobility product manager for Saft, wrote this article for
TOHE as part of the annual Executive Viewpoints series.
TRUCK & OFF-HIGHWAY ENGINEERING
BOTH IMAGES: ADOBE STOCK
Truck & Off-Highway Engineering - June 2021

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