24 “Traction drive systems have been used in construction machinery for years, but the true innovation lies in the application of ball screws, which brings a fresh perspective to the technology. In fact, Bobcat has more than 13 issued patents on the T7X, with several additional patent applications pending. “The use of the ball screws is really about the forces and application. The challenge with a loader is that you’re using this one piece of equipment for a whole bunch of jobs. It doesn’t just have one application, like a lawnmower. It’s a tool carrier, and the ball screws work beautifully in this application.” The motors are coupled to a 72.6 kWh lithium-ion battery, chosen with the aim of at least matching the performance of the diesel-powered equivalent. It is sized such that each one of the motors can independently draw its maximum potential, so there is not one motor that would limit the power of another motor based upon its state. Battery capacity was selected to provide ample working time before requiring a charge. To determine just how much energy was actually needed, the team spent time researching the typical workload of their diesel hydraulic version. This resulted in some interesting findings about how much energy is actually used in everyday operations. Honeyman explains: “Most construction equipment is only actively used for about three hours per day, and because diesel hydraulic machines need to be on ‘idle’ to build torque capacity, they spend about a third of the day just idling and burning fuel. An electric machine does not need to do that, so that’s a significant reduction in required energy every day.” The battery contains just over 5,000 cells, which are 18650 nickel manganese cobalt oxide (NMC) in type. When the machine is in normal operation it draws a continuous power of about 40 kW, but this can increase with higher workloads or performance to a peak of around 80 kW, although this will clearly drain the battery more quickly. Charging is done through an onboard, 6.6 kWh charger, with a full charge taking about 10 hours when plugged into a 220 V outlet, although there are also plans to implement fast charging. The system’s architecture also makes it possible to charge on a remote site without plugged-in electricity using a standard, 220 V, 30 A generator. Reducing components The use of electric power for both the drivetrain and work operations has resulted in far fewer component parts, and far less coolant and fluid in use, compared with the diesel hydraulic equivalent. In total, Pfaff says there are now 50% fewer parts and just under one litre of eco-friendly coolant is required, compared with the 216 litres of fluid in the T76. Pfaff explains: “Most construction equipment requires huge cooling packages for the engine, hydraulics and AC system, and in compact machines that becomes much more noticeable. In this machine the cooler is relatively smaller, and we only need a small amount of fluid running through the traction drives and motor controllers to keep them at temperature. “In terms of components, every fitting hose, connector, adapter and harness is not just a cost, but also added complexity and risk in terms of runtime. On a diesel hydraulic machine, you have an entire engine, pumps, hoses and multiple individual moving parts, but on the electric loader the componentry is reduced with just a battery, some electric drives and wiring. “From the outside it is the same machine, but the difference inside is dramatic. It’s far less complex from a piece-part perspective and that should make a lot of people excited, because while our diesel-hydraulic machines are very reliable, each one of those parts represents a possible opportunity to slow down or end your work for the day.” That component simplification made it far easier for the team to turn that original concept-proving prototype into a machine that has now been sold and sent out to construction sites across North America. Although having to fit in larger system blocks did, ultimately, require changes in some areas of the base machine, its development was still very fluid. “These machines are compact and everything is very tightly packaged,” March/April 2025 | E-Mobility Engineering Charging is easy, but the efficiency of operation means the vehicle does not need to be charged as regularly as you might think
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