21 E-Mobility Engineering | March/April 2024 components were communicating consistently and that all systems were always working, free from any errors that could be caused by one ECU missing a critical data input. An additional part of the integration challenge was that many items inside the boat’s infrastructure were totally new to the automotive-focused Porsche team. For example, to begin with, the team did not know what NMEA buses (a comms standard for connecting marine sensors and displays within vessels) were, how to read the throttle lever, or how to control a seawater pump for thermal management (although the latter did turn out to be a fairly simple 12 V on/off type of system). Other hurdles of this type were also cracked fairly quickly, despite the team being used to things like LIN buscontrolled pumps with sophisticated error messages in their usual automotive projects. Hence, combining these two worlds in software was the biggest singular challenge of the overall project from the Porsche side. The bulk of this development was completed in the 12 months following the first talks between Frauscher and Porsche. The first working prototype of the eFantom was presented to the Porsche AG board in November 2022. Inside the 850 The e-powertrain components are laid out as appropriate for the shape and dynamics of the boat. For instance, the high speed of the eFantom, compared with Frauscher’s other electric boats, means that hydrodynamic lift causes it to plane out of the water at its higher continuous power levels. This is why the stern drive sits at the very back, to ensure continued thrust while planing. The e-motor sits inside the back of the hull, connected to the stern drive via a short transmission shaft. This enables the former to control the latter directly, much like a conventional outboard with a shaft and screw transmission system. The inverter is mounted forward from the electric motor, while the controls unit containing all of the powertrain’s ECUs sits atop these two inside a sealed (and Porsche logo-stamped) enclosure. The battery is installed under the rear lounge deck, running from the mid-section of the boat back to the front of the inverter. Above the back part of the battery pack is a series of metal structural supports and a heat exchanger for an active liquid-coolant system for thermally managing the batteries, the inverter and the e-motor. The main HV bus running from the battery is an 800 V network, with both AC and DC fast-charging ports accessible on the front side of the left bench in the lounge area. Smart integration also required that the Porsche team spring and damp the powertrain effectively. To that end, the engineers asked Frauscher things such as the rules of thumb on the ranges of acceleration that the boat would impart on the electrical components. Such parameters have not previously been studied at length in boats, as they have in the world of road EVs. Discussions between Porsche, Frauscher and the naval architect led to a belief that the team would need to damp for up to 5 g of acceleration. However, other companies told Porsche over time that they had measured over 50 g with power boats on lakes. To complete the study phase (and as the boat lacked any kind of chassis as commonly used in automotive vehicle construction), the Porsche team screwed the battery pack directly onto a prototype eFantom’s hull and took it out for lake testing to gain its own data. Porsche’s noise, vibration and harshness (NVH) specialist installed acceleration sensors around the battery, the boat hull and on other components. The team found measurements consistently higher than 5 g. Additionally, the vibration profiles (measured as accelerations over different frequencies) were far wider and more dynamic than was typical in road vehicles. This inspired the team to look into marine suspension components, and they found some designs for spring dampers already in wide use. Some mechanical adaptations were also made at the battery frame, particularly using wire rope mounts to keep the pack as internally unchanged as possible and to mount it to the spring dampers. The boat's ECUs are handling hundreds of signals at any given moment, including tracking of key health and performance parameters for the driver's display at the helm
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