E-Mobility Engineering 014 l InoBat Auto dossier l In Conversation: Brandon Fisher l Battery monitoring focus l Supercapacitor applications insight l Green-G ecarry digest l Lithium-sulphur batteries insight l Cell-to-pack batteries focus

“All the curves for power, torque and speed are set in-house through our control algorithms, and we invested a lot of time and money into setting those performance dynamics correctly. “Doing that was important, because the ecarry’s weight and inertia change hugely between being empty and fully loaded, so we had to build our own control strategy for the sake of features such as stable regeneration and driver comfort – sanitation workers hate feeling a ‘punch’ in the stomach when releasing the accelerator pedal. “Our algorithms for the inverter and motor guarantee smooth motion with the same acceleration and deceleration regardless of the speed, payload, and incline or decline the end-user is driving on.” Aretino adds that the regenerative braking enables up to 25-26 kW of power to be generated through the ecarry’s powertrain (typically sustained when on a downward slope). The motor control algorithm also includes vector control functionality for locking in the rotor angle, enabling functions such as hill-holding along with the desired precision of torque and rpm targeting for smooth driving and transients. Charging strategy In addition to this recouping of battery energy, Green-G aims to provide as many charging options as possible, to ensure the ecarry’s batteries can be replenished from effectively any AC source, as available charge points are still few and far between in many places. The standard issue 7.2 kW monophase OBC was chosen to suit the widespread 32 A outlets available across Italy’s industrial and commercial centres. Practically any industrial connection, down to the very lowest power inputs from homes, is compatible with the ecarry. “For every charging level and protocol there is, we take the specification and then develop the compliant protocol in- house,” Aretino says. “We do that because we want to understand every aspect of how charging is managed through the control software, to ensure power is always requested from the charging stations in a clear and safe manner, and results in the best, most efficient recharging performance possible.” He adds that this is also enabled through the provision of Mennekes charging cables, three-phase to single- phase 32 A adapters, and a range of other charging accessories. “We also have clients asking for fast DC charging as well now. We’ve developed everything needed for CHAdeMO-type fast charging, and we’ll soon be able to install CCS systems on the ecarry too, upon request,” Aretino comments. Thermal management All electric and electronic components on the ecarry are thermally managed using liquid cooling, principally because its waste collection operations will require slow speeds and high torques. Not only does that mean insufficient airflow is generated for cooling any components, but more heat and stress is generated than a typical EV because of the higher torque and hence current density. “One of our ecarrys has been used for more than 10,000 km now, across very hot as well as very cold environments, and in several trials we ran it without activating the liquid-cooling circuit in the batteries. To date, that vehicle has had no problems with its batteries. “Also, Webasto installs cryptography on its batteries, so on the off-chance someone tries to steal the packs, they can’t be used by anyone else, it’s a closed comms system.” Drive systems The inverter and motor are mounted closely together on the rear axle, as would be expected in a heavy-duty rear-drive vehicle and powertrain, with a single-speed transmission and a 12.55:1 reduction ratio. That, combined with the programming of the inverter’s ECU, limits the ecarry to a safe top speed of 80 kph. The motor is a permanent magnet machine operating on a nominal 350 V input, which outputs up to 90 kW at peak power, up to 380 Nm of torque and 60 kW of power during normal operation. The inverter is designed for a peak power supply of 400 V and matches the nominal rating of the motor at 60 kW. “We’ve also chosen a motor built around a hairpin stator, as we feel that will maximise the torque density,” Aretino says. Several options for charging connections are supplied, to ensure the ecarry’s drivers can replenish their batteries from any available input All the electric and electronic systems are liquid-cooled to compensate for the slow-speed, high-torque drivetrain 54 Summer 2022 | E-Mobility Engineering