Challenges of introducing lithium-ion batteries in underground mining

A Komatsu Joy battery hauler in an underground mine. Lithium-ion (Li-ion) batteries have transformed many of our modern products, from cellphones to laptops to electric cars and trucks. There are real benefits to this type of battery for aspects of underground mining, and Komatsu is deep into exploring their use. Komatsu’s first underground Li-ion product is the Joy BH-18/20 series of battery haulers, with the first units delivered in 2017. These untethered machines have traditionally been powered by lead-acid batteries, but there are major benefits with Li-ion batteries. The BH haulers’ Li-ion batteries charge in about two hours, require almost no maintenance, are 25 percent lighter (less machine wear and tear) and can last an estimated seven to 10 years. There is no watering; they can be opportunity-charged during a lunch break or continuous miner bit changed for added operation, and their smooth voltage delivers accurate performance levels and battery-health metrics. There are more than 450 Joy battery haulers in operation, with 15 running Liion since 2017. One major benefit is an operation with lead- acid haulers can easily be converted to Li-ion operation. The Li-ion battery envelope is the same and connects the same — it is compatible with existing AC fleets. The battery itself is in its second generation. Generation 2 uses a lithium-nickel-manganesecobalt- oxides (NMC) chemistry that is designed to provide 220 kWh of total energy for more than eight hours of operation. It includes wireless communication and an explosion-proof-rated enclosure (versus IP-rated). Like any new mining technology, there were challenges in developing Li-ion batteries and chargers for underground mining, especially as the industry drives toward zero harm. Underground mining conditions can be difficult, with confined surroundings, a hostile environment, logistical challenges, and a potentially explosive atmosphere. These considerations were an integral part of Komatsu’s design and testing process. Because Li-ion batteries are a new technology for the industry, the standards and regulations have not been finalized. Existing standards and regulations do not specifically address Li-ion battery equipment, but they are in progress. The Global Mining Guidelines Group (GMG) is now on version three of its recommended practices for battery-electric vehicles in underground mining. There are some further guidelines from the Canadian Standards Association, specifically M424.4:22 on self-propelled, electrically driven, nonrailbound mobile machines for use in nongassy underground mines. The International Electrotechnical Commission (IEC) is also revising its existing explosive atmosphere standards. Using these guidelines (even as they evolved), the Komatsu team tackled key battery considerations. What chemistry would be used? Which types of battery cells would work best — cylindrical, pouch or prismatic? How does the team balance the size of the battery for weight and packaging sizes with the length between charges? Commitment to safety at all levels of the battery system As Komatsu team members made these decisions, they considered safety at every level of the Li-ion battery system. After choosing the chemistry most appropriate for the application — NMC with a generation 2 battery — the team carefully vetted suppliers for their quality reputation and processes, and thus began a rigorous testing and validation program. A rugged design and thermal management of the actual battery modules and packs were also key drivers. The generation 1 version used 15,000 cells; generation 2 uses 2,400 pouches, reducing wiring and monitoring stress. Sensors throughout the modules and packs deliver continuous and accurate monitoring and diagnostics. All the packs are managed by a battery management system (BMS). The BMS continuously monitors the state of charge and state of health to help ensure performance and safety. Parameters from temperatures, voltages and current to safety interlocks and cell balancing are monitored. This is where the wireless capability of the generation 2 batteries and charger is important. All the battery data is sent wirelessly to the charger, which then can be uploaded to the cloud via the mine’s communications system. The data are monitored by Smart Solution centers, and if something such as elevated cell temperatures is detected, warning text messages and/or emails will be sent to the mine and Komatsu service engineers. If the situation gets worse, a fault message is sent, and the battery will automatically disable its affected pack for safety. Figure 1 The Franklin lithium battery charger. What about the battery compartment itself? The battery compartment needed to be easily removable for swapping batteries and to fit within the current BH battery hauler envelope. The tray is a heavy-duty construction of a 20-mm (0.78-in.) plate and has separate and vented compartments. A circuit-breaker interface to the machine and charger is included, and it is IEC/ATEX certified. At the highest level, the mines can benefit from more accurate gauges and diagnostics because of the integration of the vehicle and charger; it is equipped with a “limp home” mode for the vehicle at low charge levels along with overvoltage protection at the charger. Regenerative braking is also enhanced to help with easier operator use and safety with the Li-ion’s BMS. When the battery is near fully charged, the machine’s control system disables regenerative braking to help reduce the risk of the battery overcharging and overheating. Developing testing requirements As existing mining standards and regulations do not specifically address testing requirements, the Komatsu team developed its own testing, starting with the UN38.3 manual of tests and criteria with transport of dangerous goods certification protocol as the starting point. UL and IEC standards and tests are similar, and these tests were added by the team to the testing regimen. Since mining operators are often faced with unpredictable conditions, the development team conducted extensive abuse testing simulating mining conditions, including explosive atmospheric testing (part of IEC certification). Preparation for deployment in underground operations Whenever a new technology is deployed, it is not enough to just design, test and manufacture a solid product — all stakeholders must be prepared for deployment to ensure success and promote safety. It can be as simple as, “How and where will we stock and ship spare parts?” Or, as complex as working with regional regulators to ensure compliance. Then there is working out who performs maintenance and repair tasks: the customer, the battery supplier or the machine manufacturer? Finally, there is training to consider — creating a program for either the battery supplier or machine manufacturer to educate the end customer on this new technology. A key aspect of this is to properly train end customers on the safe use of the machines and batteries to help prevent any possible incidents. The Komatsu design team studies and tests for an exhaustive list of possible incidents — in this case, gaseous emissions, smoke and fire. It then collaborates with mining operations and authorities to help assist them in developing their own mine emergency response plan. What about charging? The development team searched for a charger to meet the needs of these new batteries in rigorous mining conditions. There were good products, but none that matched the requirements closely enough. So, the team decided to develop the Joy Li-ion battery charger. To meet the durability needs of the rugged mining environment, the charger development team looked to components from Joy mining equipment, including shuttle cars and shearers. The drive system has the same OptiDrive experience customers using Joy products know and it is key to rapid charging times. As mentioned, the charger does more than charge. It monitors battery health and works as a communications hub with both CANBus and wireless connections. The charger has been so well received that Komatsu is rolling out versions for Li-ion-battery hard-rock machines, surface mining dump trucks and construction machines. Komatsu Joy BH battery haulers are the first Li-ion-powered equipment in underground soft-rock mining, meaning Komatsu not only had to develop a new product to help improve customers’ operations, but also had to create the design and testing process with regulatory agencies and customers. It is a process that is still evolving as battery technology and the regulatory environment also continue to evolve.

Challenges of introducing lithium-ion batteries in underground mining

Authored by:
Jerry Davis

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