54 January/February 2024 | E-Mobility Engineering a controlled temperature before being removed from the mould and trimmed around the edges. This process is well suited to complex shapes and yields parts of consistently high quality with good material properties and, often, lower weight than parts made using other processes. Infusion moulding also produces lower emissions and less waste than comparable processes. Reusable vacuum bags made from a silicone material as used by RS Electric boats eliminate the waste associated with disposable bagging. Further, the foam cores are partly made from recycled polyethene terephthalate (PET) plastic bottles. As an option, the company also offers consoles made from a plant-based composite material that uses flax fibres for reinforcement. Optimised battery placement From a trim and weight point of view the decision was taken to place the batteries inside the central portion of the hull. “We’ve seen that a lot of people have taken a RHIB and just put the batteries at the back of the boat on the deck, which then affects the trim so that the boat is just sort of pushing water and having the weight so high makes them much more unstable. We’ve designed it to have the battery pack under the floor and we can then distribute the weight exactly where we want it to get the trim of the boat right,” Jon Partridge co-CEO of the RS Marine Group adds. “If people wanted extra seats on the boat, then we’d move the battery pack forward a little to counteract that change in weight distribution.” To protect the pack from water ingress, it is doubly encapsulated, Partridge explains. The pack itself is a sealed unit, and it is installed in a sealed metal battery box with internal reinforcing structure. The box is watertight, marinised and protected from the ingress of contaminants to the IP54 standard. “No water will be able to get into the actual batteries even if the deck flooded and it managed to get into the battery box. It can take about 30 or 40 litres before the water even touches the pack, and even then it won’t be an issue,” Partridge says. Integrated into the pack, the BMS has a major safety role in monitoring temperatures and, ultimately, shutting the battery down if it senses a temperature trend that indicates an incipient thermal runaway. The initial series of Pulse 63s were fitted with a 400V, 46 kWh Gen4 modular lithium-ion battery pack from Hyperdrive (now Turntide) designed to be recharged 2000 times to more than 85% capacity. Each module is individually controlled, conditioned and managed through a power distribution unit (PDU), and can be monitored through the RADlink datalink from RAD Propulsion, which supplies the boat’s electric outboard drive system. The physical integration connects 10 modules in a fore-and-aft line, with the 12V service battery ahead of the foremost module and separated from it by a bulkhead. More than a datalink, RADLink is described as a smart and connected vessel control unit that implements the NMEA 2000 standard. According to the US National Marine Electronics Association, NMEA 2000 describes a low-cost moderate capacity bi-directional, multi-transmitter/ multi-receiver instrument network to interconnect marine electronic devices. The boat also has an onboard charger rated at up to 6.6 kW, plus infrastructure to accept CCS DC fast charging, which is becoming more common around marinas and harbours. On average, such fast chargers deliver up to 75 kW, Partridge notes, adding that a 20% to 80% charge takes around 25 minutes, whereas zero to 100% takes about an hour. Liquid cooling The battery pack is liquid cooled, using a pumped water ethylene glycol mix that passes through a heat exchanger. Also liquid cooled, the inverter uses silicon insulated gate bipolar transistor (IGBT) switching technology and delivers up to 40 kW. The propulsion motor could be described as liquid cooled, but only by virtue of being in the water in a housing that has a large surface area exposed to the water, providing all the heat transfer capability the motor needs. Digest | RS Electric Boats Pulse 63 Designed for electric propulsion, the hull accommodates the main lithium-ion battery pack and the service battery low in the central portion of the hull to optimise weight distribution in the boat (Image courtesy of RS Electric Boats)
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