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

“On top of making enough space for 8 hours’ worth of batteries, we needed to install them where they were low enough to be manually removed and replaced. This takes place while the excavators’ cabins are stationary,” Van Hal adds. “We’ve put a lot of componentry and software intelligence into the battery packs to ensure they can charge from a wide range of inputs.” At 17 t, the DX165W Electric weighs around 1-1.5 t more than its diesel- powered equivalent. While weight reduction is an advantage for most EVs, construction excavators must be extremely rugged, so minimal structural changes have been made, and those that have still use mainly steel for robustness. Replacing the IC engine with battery packs has for instance widened the lower chassis of the DX165W such that its widest point is now 2.5 m, rather than the original 2.45 m. The DX300LC Electric has been similarly increased in size and weight, with the original weighing just 30 t to the EV’s 34 t. “We made other structural changes to prevent the electrification resulting in too much of a weight increase,” Van Hal says. “For instance, most of the ballast in the original two excavator models was replaced by battery weight. “Weight distribution is an indispensable foundation of how excavators move and operate safely. So a lot of practical measurement and CAD simulation was performed to understand the weight of the engine, the ballast, all the other heavy components, and how each contributed to the overall weight distribution, in order to understand what we had to recreate when choosing where to place all the electric powertrain systems. “We eventually came to the conclusion that we didn’t really need any of the original counterweighting thanks to the mass of the batteries. So out of the original 3.5 t of ballast on each vehicle, there’s only a 600 kg steel plate left.” Swappable battery packs As mentioned, the HV buses in the electric DX165W and DX300LC operate at 800 V. That is achieved through the design of the proprietary battery system known as the PowerBox. Developed by ECE, each PowerBox contains four CV Standard battery packs supplied by Webasto – two in series, two in parallel, each pack containing 35 kWh. The DX165W Electric contains two PowerBoxes and hence stores up to 280 kWh, while the DX300LC Electric carries three of them for a total of 420 kWh. Each PowerBox is roughly 135 cm wide, 107 cm long and 130 cm tall, and weighs about 2.2 t. “When we were looking for a battery supplier, we wanted one with good experience of heating and cooling, because these vehicles needed to function in the Norwegian winter as well as the southern European summer,” Van Hal says. “We also wanted a supplier in Europe, to ensure our supply chain resilience. A lot of our r&d took place not just during the Covid-19 worldwide lockdowns, and also when the Evergreen container ship blocked the Suez Canal and much of the international shipping. So we couldn’t entrust our future to the potentially onerous shipping times from China, not to mention the lack of face- to-face support from working with partners outside of Europe.” This r&d was also performed with key assistance from Webasto. It customised the design of the packs to the specifications given by ECE to suit the construction vehicle environment and swappability that the latter sought to tackle in the PowerBox architecture. distribution unit (referred to in-house as the ‘roundabout’) which delivers power at 800 V to the motor/inverter, electric fans, the LV DC-DC, onboard charger and other HV components. These sit between the batteries and the counterweight. Power from the electric machine directly drives two hydraulic pumps for digging. One is for the lifting boom and arm, the other is for the excavator bucket and wheels. Van Hal comments, “800 V is high, and it’s still not that easy to find components for 800 V batteries, powertrains and HVACs, but to efficiently achieve the torque needed by the hydraulics in our machines, it’s important that we go for higher voltage and hence lower currents.” He notes that both lifting and traction consume huge amounts of energy on excavators. He estimates that when driving at around 40 kph, the electric DX165W and DX300LC consume about 60 kW and 70 kW of energy respectively, although the vehicles will rarely exceed 35 kph, and drive mainly just at the start and finish of a typical work day. When lifting and digging, an average of 25 kWh is used per hour, so with up to 2 hours of driving and 8 hours of work potentially expected per day, onboard energy storage of at least 200 kWh is needed. Webasto’s CV Standard battery packs are used in the PowerBoxes; each one contains 35 kWh and uses Samsung SDI prismatic NMC cells (Courtesy of Webasto) 24 January/February 2023 | E-Mobility Engineering