Barminco is testing a prototype 65-mt Sandvik BEV truck at AngloGold Ashanti’s Sunrise Dam mine in Western Australia.
(Photo: Sandvik)
Developing a BEV Strategy
for Underground Mining
Battery-powered equipment differs, but the results are the same:
less emissions and better performance
By Steve Fiscor, Editor-in-Chief
BEV technology, as far as battery chemistry and charging, has stabilized. Even though it’s not evolving as rapidly as it was a few years ago, mines still need to keep an open mind and take an agile approach toward implementing BEVS. While one would think that the justification process would depend on the price of diesel (and it does), several other benefits also aid in making the decision. The air is cleaner, which is a benefit for all the miners underground, and there’s less vibration on the machines. Because of the tractive force, the loaders crowd the pile more effectively. Improved drivelines allow higher top speeds. Productivity and availability increase, and the machines handle better.
The use of BEVs reduces the mine’s carbon footprint and it could lower operating expenses (opex) for existing mines and capital expenses (capex) for new mines. It seems counter intuitive, but switching the fleet to electric power at an existing mine could reduce the mine’s power bill. The machines have no emissions and run cooler than internal combustion engines (ICE), so the mines do not need to move as much air through the headings, which would reduce the electrical load on the fans. During the design phase for greenfield operations, moving less air through the mine could mean fewer shafts and raises, which lowers capex significantly.
For those who are thinking about making the leap, three original equipment manufacturers (OEMs), Epiroc, Normet and Sandvik discussed their mining product lines, shared their thoughts and talked about what they are seeing in the field as far as adoption-related experiences.
Sandvik Sees BEV Interest
Growing
In terms of Sandvik’s Underground
Load and Haul business, the sale of
BEVs account for well over 10% of total
sales today. A couple of years ago, it
was in the low single digits. “Interest in
BEVs and sales of the equipment are
growing at a very high and stable rate,”
said Jakob Rutqvist, BEV commercial
director, Sandvik.
Mines around the world pay very different prices for diesel and a mine operating in a country with high diesel prices would likely have a strong BEV business case. Rutqvist estimates that roughly one-third of the world’s underground mines have a solid business case for operating BEVs already today.
Calculating the return on investment can be tricky. The cash flow profile will be a bit different from an ICE investment. “The BEV represents a greater upfront investment with a lower opex,” Rutqvist said. “The OEMs allow the mines to lease the batteries, which transfers some of the capex to opex, and that changes the profile to look more like a diesel fleet. If a mine puts 27,000 hours over five years on a machine, then we start to see an equivalent total cost of ownership (TCO).” TCO is capex plus opex over the life of the machine.
When the calculations approach TCO equivalent, the BEV decision becomes a no-brainer when the mine considers all the other benefits. “The mine, however, should not expect a dramatically lower, immediate cost of ownership,” Rutqvist cautions. “It could happen, especially if the mine is paying high diesel prices, but the realistic goal is a comparable TCO over the machine life and then all the other benefits; better air, less heat, no CO2, higher speeds, etc.; come for free.”
Once the mine gets past the initial learning curve and operations begin to stabilize, Rutqvist said they should see high availability and productivity numbers. “The Brucejack mine in British Columbia, for example, has been operating Sandvik BEVs for a while and they are very comfortable with it,” Rutqvist said. “They are consistently seeing more than 90% availability on their BEV truck fleet. We also have examples of where the technology was just implemented, and those numbers are not that good.”
For that reason, Rutqvist likes to talk about recognized potential. “When BEVs work well, availability is really high,” Rutqvist said. “That doesn’t mean that every mine will experience spectacular availability from day one. The electric driveline is very robust with fewer moving parts and fewer service interventions than a traditional mechanical driveline. As the mine gains more experience, they have the potential to achieve higher availability. Mine site readiness planning is key to high performance, you can’t just drop this technology down on a mine site without careful preparation.”
The speed of a fully loaded BEV truck on grade is almost perfectly proportional to the power, Rutqvist explained. “The power is limited by the battery’s discharge current, not the traction motors on the machine,” Rutqvist said. “If you compare BEV trucks and loaders to ICE, we get 30% to 40% more power typically on the trucks and even more power, maybe 60%, to 70%, on the loaders. That does not translate one to one for speed however.”
A 50-ton Sandvik truck, for example, achieves a 20% to 30% higher max speed than the 50-ton ICE truck. “In a mining cycle, however, it’s the average speed that’s relevant,” Rutqvist said. “The operators spend a lot of time on the ramp, but not all of their time on the ramp. Over a full duty cycle, it’s not uncommon to see 10-20% productivity improvements.”
Traction power and speed are important for trucks. The tractive effort, or how hard the machine can push, is more important for the loader. “We are currently seeing 50% more tractive effort compared to similar sized diesel-powered machines,” Söderlund said. “You can crowd the bucket harder into the muck pile, which improves loading efficiency. What sort of knocks the socks off the operator is the power they now have to push against the rock and how easily the bucket fills.”
Battery Swapping
and Charging
Swapping a battery on Sandvik equipment
takes less time than refueling Sandvik
ICE equipment, but it happens more
frequently. With the loader, the battery is
typically swapped once per shift and then
between shifts. The trucks usually get a
2- to 3-hour run, depending on the use
and the operators will swap the batteries
two or three times per shift.
As far as recharging, it depends on how much the battery is depleted, but the battery can be recharged in about an hour. “If the mine is swapping batteries, the speed of the charge is not a concern if the runtime is 2-3-4 hours,” Rutqvist said. “An aggressive charge time creates more heat in the battery and reduces battery life. If the machine doesn’t need the battery, there’s no point in having it fully charged two hours before it needs to be swapped.”
Because the runtime is so much longer than the charge time, two loaders can share one swap station. “If the loaders have a 4-hour run time, each machine will swap batteries every two hours, which is still twice as long as the fastest charge time,” Rutqvist said.
When battery life degrades to 70% or even 60% depending on the requirements in the application, it needs to be replaced. Which in calendar time would be about three years for a hard used truck. The timeframe is longer for the loaders as the average power is lower and fewer swaps needed per day. A loader battery can last 4 years or even longer.
“If a mine really wants to maximize battery life, they will place the new battery on the highest power application, which would be ramp trucking typically,” Rutqvist said. “Because Sandvik battery modules are interchangeable, they can be swapped from the truck to the loaders, which is less demanding and then you can run the battery life down further, meaning longer calendar time before needing a replacement investment.”
The Sandvik charging system has two chargers and a cooling unit. “The reason we have two chargers, and one cooler is that we have two battery packs inside,” Söderlund said. “One powers the front of the machine, and one powers the rear. Depending on the use, chargers can sometimes be shared with multiple machines. The mine can share charging stations and share extra batteries between many machines as it scales up the BEV fleet.”
The standard configuration is two batteries per machine, one is on charge, and one is on the machine. “For larger fleet we recommend an additional battery per three to four machines,” Söderlund continues. “The extra battery is a backup to cover during maintenance. The extra batteries are cycling in production, they are not sitting on a shelf somewhere.”
Implementing BEVs
at the Mine Site
When implementing BEVs at an existing
operation, it’s important that management
and the miners keep an open mind
and remain agile. This new technology is
new for the people working underground
too. They need to be properly trained on
slightly different skillsets.
Sandvik recommends that the mine develop a BEV champion for the mine site. “Operator acceptance of BEVs has been very good, but it also means change, not only for the operators, but also maintenance of the equipment as well as planning and designing the charging infrastructure,” Rutqvist said. “If the mine doesn’t have a BEV champion, the initiative could easily lose steam.”
That person needs to be involved with operations at the site rather than a corporate representative. Otherwise, the initiative could be seen as a top-down mandate from corporate. Seeing the equipment in operation either at a mine site or even Sandvik’s test mine in Finland or customer experience center in California is also important.
Rutqvist views the design flexibility of Sandvik’s charging bay as one of the features that sets its system apart from the others. Really, the mine only needs power and reasonably flat ground. Because the machines load and unload their batteries without a crane, there is a lot of freedom as to how the bays are designed.
The traffic in and out of the charging bay shouldn’t interfere with other traffic underground. “This is always a balancing act,” Rutqvist said. “The charge station should be as close to the working area as possible, but it should not block traffic to the face or a workshop.”
Because the trucks make more frequent swaps, the charger should be placed close to where the machines are working. “These problems can be easily avoided with planning and creativity,” Rutqvist said. “For example, if the mine has a passing bay, where the trucks stop and give right away to other vehicles, a charger could be placed there, and the battery could be swapped while the traffic passes.
Even though the process of lowering the battery and picking up the new one is fully automated, someone (typically the operator) still needs to connect and disconnect the battery to the charger. A jib-arm bolted to the back makes cable handling a little easier.
The batteries are smart, and they do not need to be manually monitored. Most of the critical communication happens between the machine and the battery. The battery system controller is the master for the safety system. It monitors all the critical thresholds on the battery like temperature, voltage, and current. “If the machine is trying to do something that the battery does not want to do, like trying to pull more current than the battery wants to share, the battery will protect itself,” Rutqvist said.
Maintaining the Equipment
Sandvik takes an open approach to batteries.
They sell them and they lease
them under Batteries as a Service. The
company also offers batteries with service,
where the mine owns the BEV (and
the battery) and Sandvik is looking after
it with a service contract. “In most cases,
battery maintenance is not distinguished
from machine maintenance,” Rutqvist
said. “The people looking after the batteries
are the same people who are also
doing the maintenance and repair work
on the machines.”
For the mines that want to be self-sufficient, they usually have an initial 18-month service agreement with Sandvik that covers the training period. “In most cases, Sandvik still has expertise on site after that,” Rutqvist said. He said he expects some customers as they get more comfortable, for example mining contractors, to eventually want to become experts in battery maintenance themselves.
Miners or contractors would never open the individual modules and work on battery cells. If a rare cell failure occurs and the battery module no longer works correctly, it becomes a replacement item — a consumable essentially, or “the new fuel.”
For the service area, Sandvik recommends installing one charger and one cooler. “They can use that for rapid charging if needed, which makes the servicing process faster,” Rutqvist said. “The machines can be serviced with a low-power charger also; it would just take more time for some of the routine tasks. The service bay would also need it for capacity testing, which is recommended once a quarter at least. The battery is fully discharged and then fully charged to determine the capacity level. That process goes much faster if they have a high-power charger.”
If the operator drains the battery, where the display in the cabin says 0% for whatever reason, a technician can unlock another 10%, which should be enough to get the machine to a charger. “More mines are looking for battery data and we are working on improving the telemetry,” Söderlund said. “We have remote monitoring services for diesel equipment where we have services built on top of the data and analytics. That is still being developed for the BEVs.” Sandvik acquired a battery analytic company two years ago specifically for that purpose.
On the development timeline, Sandvik BEVs are now third generation. The company is comfortable with the technology and looking to expand its offering. In the next few years, miners will see automation systems for BEVs, improvements with telematics and supporting technologies.
Epiroc Takes a Different
Approach
For BEVs, Epiroc has opted for different
approaches depending on the application.
For its loaders and trucks, the
company offers both onboard and offboard
charging. This is a great benefit as
charging strategies often change during
the life of the mine. When it comes to drill
rigs, the battery is charged onboard as
soon as the rig is connected to the grid.
“We have some customers that prefer onboard charging and others that like swapping batteries,” said Franck Boudreault, underground application expert electrification at Epiroc. “Onboard charging reduces the availability and utilization of the vehicle, but at the same time it simplifies utilization from the infrastructure point of view. The only thing the BEV needs to charge is a parking spot with a charging post.”
The typical 14-mt Epiroc BEV loader will have five hours of utilization. “With the battery-electric loaders, we’re talking pretty heavy utilization,” Boudreault said. “Unlike drill rigs, they always rely on their battery to perform their main job. In applications, such as mine development, it is crucial to clear a round on a single battery charge, which is not a problem. Autonomy will vary depending on how the equipment is driven, 3 to 6 hours, but charging can be done just under two hours.”
Boudreault explains that performance and charging speed depends among other things on the battery chemistry. “You have to choose which sweet spot you want to aim for,” he said. “Looking at the application usage of loaders and trucks, we definitely opted for maximizing energy on board through battery capacity.”
Epiroc focuses on usable battery capacity, not nominal capacity, as this is what matters for customers. For example, the Scooptram ST18 SG has 450 kilowatt-hours (kW) of usable battery capacity. “High battery capacity does not only lead to longer driving autonomy, but will also extend the overall battery life as it is not put under the same stress.”
Epiroc partnered with Northvolt on battery development, a junior Swedish company soon to deliver the world’s greenest cells. “We were the first customer to sign up with them,” Boudreault said, “which gave us the focus needed to develop batteries tailored for underground mining. After a very detailed study and valuation process, we decided on a nickel manganese cobalt (NMC) battery, which differs from the conservative trend toward lithium iron phosphate (LFP).”
The first generation Epiroc BEVs were smaller and involved other partners, dating back more than 10 years ago. Boudreault chalks the first approach up to a great learning experience. “We discovered a lot, and we could pinpoint where we wanted to be with this new offering that we currently have today,” he said.
Today, Epiroc’s batteries have a builtin thermal management system. It maintains the optimal cell temperature whether the battery is charging or discharging. The Epiroc BEV mine trucks now have a more efficient drive train, compared to the earlier generation. “The battery on the new 42-mt capacity truck has probably three times the capacity of the original 20-mt truck with a thermal management system,” Boudreault said. “As importantly, we have optimized the driveline for battery-electric drive and considerably reduced losses.”
Batteries With and
as a Service
Epiroc offers both Batteries with Service
and Batteries as a Service (BaaS) and
confirms that its BaaS program offers
miners several benefits. When comparing
the costs, there was one price for an
ICE machine. With a BEV, the mine must
purchase the machine, but also address
batteries and charging equipment. The
upfront cost for a BEV is higher than ICE
equipment and, once the batteries and
charging equipment are added to the
invoice, the customer
can suffer
sticker shock.
“With BaaS, we can move the batteries from the capex side of the calculation to the opex side,” Boudreault said. “In a sense, the mine is leasing the batteries. We can handle this because we already have technicians working with our customers on advanced equipment around the world. So why not offer this as a first class service by Epiroc to enable peace of mind.”
Epiroc launched BaaS in 2018 and last year it began to offer Batteries with Service for the mines that prefer to own their batteries. “Regardless if a customer wants to purchase or lease the batteries, Epiroc will take the responsibility of battery maintenance,” Boudreault said.
BaaS includes a certain level of utilization. The mines pay a monthly fee and they get a certain level of utilization. “For a loader running on two batteries, the base fee included in that would be roughly the same as the monthly utilization, so it suits that application very well,” Boudreault said. “For other applications, such as drilling, purchasing batteries may be more attractive based utilization.” Epiroc always looks at the different cases and advises the mines what direction to take.
Offboarding With Epiroc
If a mine decides on offboard charging
with Epiroc loaders and trucks, it will need
an overhead crane to swap the batteries.
Swapping bays can be designed to suit
customer needs, depending on the number
of BEVs to be catered for. “If a mine
has three trucks and one loader working in
an area, they can design that charging bay
to handle all the batteries needed for that
fleet, including the required charging cabinets
and charging posts,” Boudreault said.
One bay could charge the batteries for any number of BEVs. A larger excavation would be required, but it would have the flexibility to handle multiple types of batteries for multiple vehicles, reducing the overall need and cost for infrastructure. “As the swapping bays are modular and scalable, space-claim and infrastructure cost can be slashed compared to one-toone layout,” Boudreault says.
To be on the safe side, charging bays should be connected to the return airway. While the Li-ion batteries do not emit gases during the charging process, a small amount of heat is generated which is easily handled by ventilation systems normally in place.
To add additional layers of safety, charging bays can be fitted with sensors for heat and smoke detection like any industrial setting. “The risk is not zero, but we try to mitigate the risk first with the design of the batteries,” Boudreault said. “Epiroc has 7 million kWh of battery utilization with no incidents to report.”
Converting Existing
Equipment to BEVs
Epiroc offers conversion for two sizes of
loaders, the 10- and 14-mt machines,
and two sizes of trucks, the 33- and 42-mt
truck. “If a mine is pulling their machines
out for a major, mid-life rebuild, they can
convert those machines to battery-electric,”
Boudreault said. “An operation in
Canada is using two rebuilt 10 tonners.
Every month we see that their battery
utilization is around 25,000 kWh. All this
data is available in real time to the customer
and Epiroc through our battery
telematics system.” Boudreault stresses
that data transparency is key to drive
change management when shifting from
diesel to battery-electric.
“By optimizing mine design, power consumption can be lowered and autonomy stretched” Boudreault said. “And with onboard opportunity charging during a lunch break, coffee break, shift change, etc, the battery state of charge can be topped up. In many cases with the loaders, the mine can make do without swapping the battery.”
Acceptance Levels Are High
Boudreault said he sees two factors
driving BEV acceptance underground,
improved performance and the improved
working environment. “When it comes
to mining equipment, miners like performance,
torque, speed, hydraulic force,
etc.,” he said. “With a BEV, you have
exactly that. The traction is separated
from the hydraulics. If you want hydraulic
force, the operators do not need to rev
up the engine, they just pull the lever and
they see more power instantaneously.
“The same thing applies to operating a truck in a tight environment,” Boudreault said. “To take a tight curve, an ICE operator would typically take that at a creeping speed. The hydraulics are connected to the engine and the engine is roughly running at idle, so the steering on the ICE machine becomes difficult. On the battery truck, they run separate, and the operators could steer with one finger and go wherever they want.”
With BEVs, the working environment improves dramatically with no on-site emissions, and a lot less heat, noise and vibration.
Battery-electric Drilling
Boudreault works with battery electrification
across the entire Epiroc product line.
When he started, he thought loaders and
trucks would get all the attention because
of the different duty cycles and balancing
charging with operations. He didn’t think
the battery-electric drills would attract
much attention as they tram so little. His
assumption proved false.
After revisiting his thinking to understand why, he said he found three reasons of the interest in battery-electric drills: autonomy, speed and the plugand- play setup. “BEV drills have a battery capacity that exceeds the need, which eliminates range anxiety,” Boudreault said. “The energy the drill has on board will allow it to travel anywhere in the mine. On a full charge, the drill rig can climb 950 vertical meters or 7 km of ramp before the battery is depleted.”
The Epiroc BEV drill rigs run as fast as the optional 6-cylinder, diesel-powered rigs. Normally the diesel rigs use a 4-cylinder engine. The BEV drills move quicker than the best of the class.
Plug-and-play means that the trailing cable is connected the same way as it would be with a traditional drill rig. So, the charging takes place in hidden time. “The BEV drill rigs will run without any worries,” Boudreault said. “Zero infrastructure needed and zero extra tasks. That makes the BEV drill rig a very good entry point for our customers who wanted to have a first taste of battery electrification.”
Boudreault said he also assumed that the trucks would be a challenge due to their energy consumption. “With ramp haulage, the truck’s payload is roughly the same as the weight of the empty vehicle, so the weight being propelled up the ramp is 80 mt for a 42-mt truck, and the battery regenerates on the return trip,” Boudreault said. “The truck does not regenerate as much as it has spent, creating a deficit in the energy balance. Batteries must be swapped and we have some customers that do that very well, but it’s demanding.” His assumption was validated until the arrival of dynamic charging.
Epiroc is working with Boliden and ABB to develop a dynamic charging system, where trolley technology is applied to ramp haulage for BEV trucks. “We have our first machine going through validation at the Ravliden mine in Sweden,” Boudreault said. “If it lives up to expectations, it will pull grid power using a catenary- trolley system.”
The infrastructure in the form of the catenary-trolley system and the substations to feed them will be expensive. “When the truck is off the ramp, however, it will rely on its battery rather than trolley- systems, making its operation autonomous,” Boudreault said. This application would be well suited for greenfield projects. It would be difficult to convert an existing mine.”
Ravliden is a satellite deposit connected to the Boliden’s Kristineberg mine in the Skellefteå region. Rather than sinking new shafts, Ravliden will be connected to surface by a 5-km ramp that will be an ideal set-up for dynamic charging. Most of the ramp will be straight except for a few smaller bends and two longer curves. Boliden and ABB have demonstrated the trolley technology, operating haul trucks on the surface at its Aitik copper mine.
Normet Makes BEVs Easy
to Manage
Normet’s BEV platform is called Smart-
Drive and the company, which has over
50 offices in 30 countries, has placed
65 BEVs in underground mines and tunnels.
Normet designs and builds support
equipment for underground mining including
explosives chargers, shotcrete
sprayers, concrete trucks, scissor lifts,
personnel carriers, etc. “The sale of BEV
equipment is the first of many steps with
the customer,” said Mark Ryan, vice
president, equipment offering for Normet.
“The technology is relatively new, and a
lot of our customers are using this equipment
for the first time. We try to make the
technology as easy as possible for our
customers to manage.”
One of the biggest advantages with BEVs for Normet has been the increased ramp speed. “The electric motors are connected directly to the axles, which is far more efficient, especially when it comes to ramp speed,” Ryan said. “The BEVs have greater availability and we are able to recover energy when driving downhill.” As opposed to production equipment, which is hauling ore uphill, Normet’s equipment is hauling concrete and supplies downhill. “We are driving downhill fully loaded and we are able to recuperate energy,” Ryan said. “When we drive up empty, there is less demand on the drive train and battery. Our different applications like concrete, material, and personnel transportation and logistics, but also sprayed concrete and explosives charging, really work well with this technology.”
When Normet started to develop battery- electric equipment, they considered simply removing the engine and replacing it with a battery. Once they started to look at that approach in more detail, they realized that every machine would be slightly different, which would complicate the manufacturing process.
“We went back to the drawing board and developed a battery module,” Ryan said. “Regardless of the application, the battery module on each Normet BEV is the same. The batteries are the same. The motors are the same. The axles are the same. Training, maintenance and troubleshooting are the same too. We wanted to make it as easy as possible for our customers to implement this technology.”
When Normet compares the battery- electric models with its ICE models, the BEVs have new cabins, new control systems, new suspension system, etc. “It’s a completely new platform and as a result we’ve been able to reduce the vibration by 55% and the noise by 80% compared to the diesel equivalent,” Ryan said.
The BEVs have two 100-kW electric motors and a 90-kWh battery on board. “It’s a redundant system,” Ryan said. “If we have a failure with one of the drive motors, the other drive motor has enough power to move the machine to a safe location.
LTO batteries have a reputation for being able to tolerate high levels of abuse. “We wanted a battery chemistry that could operate in a wide temperature range, from -30°C to 50°C,” Ryan said. “We also wanted fast charging capability and a long battery life. We wanted 20,000 full charge-discharge cycles and from the data that we’re collecting, we feel these LTO batteries will reach that range comfortably.”
A common misconception is that fast charging the battery will somehow reduce its lifetime. “With this chemistry, that’s not the case,” Ryan said. “The battery doesn’t care how fast it’s charged. It doesn’t affect the life of the battery.”
Every Normet BEV comes with a charging infrastructure on top of the machine. “Operators can charge it at the face if they want,” Ryan said. “They can connect to the source that is powering the jumbos and other electrically operated machines. If the mine wants fast charging, we offer that as well with many different options.
“Once the miners start to use the machines, they stop talking about battery range and they start talking about opportunity charging,” Ryan said. “In other words, every time a machine is stationary, they have an opportunity to charge and they start to get very clever about it and range becomes less of a sticking point.”
The SmartDrive is global and can work anywhere. The Oyu Tolgoi mine, as an example, in Mongolia operates one of the biggest fleets of Normet SmartDrive machines.
When comparing ramp speed, the SmartDrive ramp speed can be over 133% higher. As an example, Smart- Drive explosives charger can ramp up at 12 km/h, compared to 3-6 km/h for diesel. “In this sort of application where the magazines store blasting agents on the surface and they are constantly tramming up and down the ramp, approximately 133% improvement could mean a significant increase in production,” Ryan says.
When a mine gets a BEV for the first time, they often understand some of the risks but not all of them. “We support the mines with risk assessments and training people to understand where the risks lie,” Ryan said. “We see it as one of the key differentiators for us.”