52 November/December 2023 | E-Mobility Engineering This excavator’s developer has taken electrification to a new level, as Peter Donaldson explains Breaking new ground Environmental legislation is providing the pressure for the development of electrified construction machinery such as the new Suncar/Hitachi ZE150W excavator. This 15 t-class vehicle pushes electrification a little further than most conversions, making use of some highpowered electro-hydraulic (EH) linear and electric rotary drives where many are more conservative and stick with the original hydraulics. The base vehicle for the ZE150W is the Hitachi Construction Machines (HCM) ZX150W-7, which is powered by a 105 kW diesel engine, has an operating weight of 15,300 kg and wields a 0.66 m3 capacity bucket. The conversion is being carried out by Suncar and Kenki Technology Group (KTEG), a joint venture between HCM and Kiesel, a German dealer for HCM’s machines. The programme began last autumn, and the team expects to complete it in the middle of next year. Next-level electrification With the ZE150W, Suncar is conducting what project leader Rik Baettig calls a “next level” electrification in which the company is facing new tasks such as electrifying the slew drive and the traction drive, and integrating an innovative EH boom actuator. “Instead of just replacing the diesel engine with an electric motor, we are partially replacing the conventional hydraulics with direct electric drives,” he says. “Except for some pilot projects aimed at elevating efficiency through minor changes to the control systems, many aspects of this project are firsts for Suncar.” Sourcing a suitable HV rotary joint to take power down to the undercarriage proved challenging. Although the original architecture of the mobile excavator already had an LV slip ring with a small number of signals, a new system had to be installed for the HV lines and the higher power. “Finding an appropriate supplier with this specific application experience and the ability to meet the space constraints was very difficult and time-intensive,” Baettig recalls. Other challenges that proved tougher than anticipated included finding the right combinations of motor and inverter for individual swing, wheel and boom drives. “It became apparent that very few suppliers have even explored the field of application required for this project, so the number of suppliers has been a limiting factor,” Baettig adds. Structural modifications to accommodate the battery pack centre on a frame designed for the purpose, which isolates the pack from vibration with dampers and also provides protection from shock and penetration. The excavator still has a counterweight to balance it, but Suncar is in the process of redesigning it for packaging reasons, Baettig explains. Modular NMC pack Supplied by BorgWarner Akasol, the lithium-ion battery pack is built from modules connected in parallel. It uses cylindrical cells with lithium nickel manganese cobalt oxide (NMC) chemistry optimised for energy density while providing a high enough discharge rate to cover power needs. The standard pack has an energy capacity of 200 kWh from two modules, with a three-module 300 kWh pack available as an option. However, the production pack configuration will depend on the extent of direct electrification that eventually makes it into series production. “For a basic low-level electrification, three modules will probably have to be standard,” Baettig says. Using an AC charger, the battery can charge at 44 kW as standard or 88 kW optionally, with powers of 150 up to 250 kW possible with a CCS2 standard DC charger, depending on battery SoC. Deciding how much battery capacity was required also presented some challenges, because there is no uniformly A diesel-powered Hitachi excavator under testing to provide data for simulations to scope out the power requirements for the electric ZE150W (Images courtesy of Suncar unless specified otherwise)
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