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

carrying packs to and from the customer’s charging station. It will feature a mobile, electrically powered, manually operated crane for lifting and moving the batteries. “Designing and engineering this swappable battery approach took weekly videoconference meetings between Webasto’s engineers and ours,” Van Hal says. “We did the primary drawings and software, while they performed important tunings and changes from their side to make sure the solution worked and was practical. “They continue to provide good development support alongside a regular supply of batteries and related components. And it was a useful partnership for them too: they now know a lot about what it takes to make batteries that work for construction sites, particularly in terms of charging systems and battery behaviours.” The swappable nature of the excavators’ battery packs means that construction yards can develop their own charging areas using whatever HV or LV outlets are available on site, theoretically close to or inside a designated battery storage warehouse. “There are also two 22 kW AC charging ports behind the cabin of each excavator, near where the counterweight plate is, so we can also recharge the packs at up to 44 kW while they’re installed on a machine in a lifespan-preserving way overnight,” Van Hal adds. “Meanwhile, there are CCS2 ports on the individual packs that allow them to be fast-charged at 140-150 kW via DC during lunch breaks.” Each AC charging port is controlled by an onboard charger from Stercom, which was selected because it is based nearby, in Germany, and hence easily contacted, as well as for its 800 V architecture – a rare quality among OBCs, ECE notes – and agile liquid cooling. The OBCs connect to the PowerBoxes, which notably control the charging and discharging of the packs such that each pack is either replenished or depleted one at a time, rather than all packs across all PowerBoxes being consistently balanced for SoC. That ensures workers can swap completely empty packs for fully charged ones. “So theoretically, each excavator can be kept working 24 hours per day, save for the few minutes it takes to replace a pack,” Van Hal says. “The software in the BMS controls the requests for charging to the OBC and the discharging to the roundabout.” Battery modules and cells The packs in ECE’s vehicles are made from automotive battery modules supplied by Samsung SDI. Inside the modules are prismatic, NMC811 cells, with laser-welded compression, retention, and busbar components for the cells to ensure consistent long-term performance. While the SDI modules come with a range of differently optimised cells, those in the ECE vehicles incorporate the HEV-type cells, which contain 5.2- 5.9 Ah each and have been optimised for power density. As Webasto explains, the excavators will often go from lifting no weight to suddenly lifting up to 2 t of earth and swinging it around. That creates Charging systems Some readers may be familiar with swappable battery concepts from their use in e-scooters, e-motorbikes and e-tricycles around the world: the packs interface with and fit into conformal slots as cartridges. The PowerBox architecture is much the same, but at a larger scale for the electric DX165W and DX300LC. As excavation jobs can sometimes run in excess of 8 hours, and such jobs are far apart from each other with only a driver and a construction worker present, ECE’s customers needed an approach by which packs could be replaced by one person with no electrical engineering knowledge, to enable a digger to continue working. The electric DX165W’s eight packs and the DX300LC’s 12 are accessible via a panel at the back. A system of HV interlocks across the packs is engaged while a given digger is working, to prevent hazardous removals. Once the digger stops working and is turned off (and thus rendering the HV networks, LV networks and HV interlocks inactive) a worker can physically unplug each pack as they so choose, and slide them out of the PowerBox’s racks via lifting points atop the packs. Given the weight of each PowerBox, ECE plans to provide a trailer for The DX165W Electric is capable of 40 kph, although it rarely needs to travel at this speed – most power is consumed during lifting while stationary January/February 2023 | E-Mobility Engineering 25 Dossier | ECE electric Doosan DX165W and DX300LC