E-Mobility Engineering 017 l ECE Doosan electric excavators dossier l In Conversation: Matt Faulks l Battery testing focus l Battery Show North America 2022 report l Ariel Hipercar digest l Cathode materials insight l Thermal management focus

their performance and determine how to optimise them, in terms of hardware configurations and software tuning. “Most important among our test objectives was getting practical comparisons of how our electric conversions performed in comparison with the original diesel-powered excavators,” Van Hal explains. “So to ensure those comparisons were accurate, we’d run drills of movements and digs with diesel vehicles we had in-house, then repeat them as closely as possible with our electrified prototypes. “Efficiency and endurance are of paramount importance to our customers, so first and foremost we’d look at diesel fuel consumption, and contrast that with the rates of battery energy consumption, to optimise that latter parameter wherever we could from pack to motor.” Before the first commercial deliveries, ECE also loaned the DX165W and DX300LC Electric prototypes to customers’ building sites for beta testing for a fortnight. That verified first- hand that the heavy-duty EVs could execute the sorts of digging, earth- moving and demolition tasks that end- users would require. Again, diesel-powered Doosan excavators were available at these sites whenever the beta testers wanted direct comparisons of the high-carbon and zero-carbon machines. Even after the first DX165W and DX300LC EVs were supplied to their customer (a construction subcontractor in Norway), talks between the end- user and ECE continued, and yielded invaluable feedback on key operational considerations, for instance on the best approaches for handling or storing battery packs. To date, 20 units are working with commercial partners, and Van Hal notes that five have gone to large construction firms, with the other 15 being used by subcontractors. A further 56 Doosan vehicles have been bought and at time of writing were going through the production process. Specification and anatomy We previously covered the John Deere 944K Hybrid Wheel Loader ( EME 03, Summer 2019), which required holistic re-engineering to transform it from a diesel system into a hybrid-electric one, owing largely to the torque and regeneration requirements associated with how loaders drive directly into earth (or other material) to scoop it into their buckets. By contrast, however, the two large Doosans are consistently stationary when lifting, and spend very little time driving around construction yards. That, combined with r&d revealing that the hydraulics used for traction and lifting were far more suitable for efficient movements of the heavy vehicles and arms than electro-mechanical ones, mean the electric powertrain is largely separate from the hydraulics. That meant the latter required effectively no modifications whether driven by a diesel engine’s shaft or an e-motor’s. As a result, ECE found that engineering the electric DX165W and DX300LC posed largely similar challenges to electrifying cars, trucks and buses. “The main challenge was fitting enough energy on either machine to make sure they could run for 8 hours at a time,” Van Hal says. “For reference, a litre of diesel contains about 10 kWh of energy, whereas the volume of a 10 kWh battery pack is much larger than a litre. “So we spent a lot of time calculating the dimensions of the batteries for different cell and module types, to then understand how much space or counterweighting we’d need to accommodate the packs.” Part of that simplicity comes from the fact that, as mentioned, the traction and lifting systems on the electric DX165W and DX300LC have been left largely unchanged, leading ECE’s engineers to the principle of “If it ain’t broke, don’t fix it”. On both EVs, the battery pack sits at the back, behind the cabin, and a heating and cooling system for the batteries is installed above (which functions independently of the vehicles) along with the BMS and a 24 V ancillary battery for cabin, control and other low-voltage systems. Some HV cabling connects the packs to a high-voltage power The PowerBoxes and their retrievable packs sit at the back of each excavator, and serve as ballast as well as energy storage 22 January/February 2023 | E-Mobility Engineering Dossier | ECE electric Doosan DX165W and DX300LC