Unmanned Systems Technology 028 | ecoSUB Robotics AUVs I ECUs focus I Space vehicles insight I AMZ Driverless gotthard I InterDrone 2019 report I ATI WAM 167-BB I Video systems focus I Aerdron HL4 Herculift

61 while lowering the overall DC resistance of the battery. “We are introducing a 6S and 7S pack built on a 53 Ah and 75 Ah NMC cell, given the popularity and flexibility of the system, although we can easily change to an LFP cell if the customer’s application requires it,” Wallace said. “It really comes down to the electronics: without the high level of BMS control that Teledyne’s technology allows, this type of system would not be possible. A CAN interface protocol also allows direct comms with the host application and any other required systems.” The company envisions the QBatt Prismatic being used for larger scale applications in particular, in which weight is less of a concern. To help that, the battery is designed to have several of its packs connected in (theoretically) endless series or parallel to create the capacity or voltage needed by the vehicle and application, with the largest system thus far being a 666 V battery for a manned aircraft. The 7S, 75 Ah pack weighs 12.5 kg and delivers 1.943 kWh for a module- level energy density of 155.4 Wh/kg. The system can be configured in series or parallel without the need for an external master BMS. To that end, VPW also promoted its BCMS battery management and charging system, which monitors all cell- level voltages, temperatures, currents, states of charge and states of health. It uses proprietary algorithms to use that data to protect against overcharging, over-discharging, temperature fluctuations in excess of the safe operating range and other issues. Ballard Unmanned Systems displayed the H2-6 multi-rotor UAV, which it has developed in collaboration with UAS manufacturer BFD Systems as a platform for the former’s liquid-cooled hydrogen fuel cell. “It’s a prototype hexacopter aircraft, and two of the six arms on the airframe body feature cooling fins that work to dissipate the heat from the 1.2 kW fuel cell stack installed in the hub,” explained Phil Robinson from Ballard. “The air pull of the propellers cools the liquid as it runs outward from the hub, before the coolant runs back towards the fuel cells to counteract the 1.2 kW of heat they’re also generating. There was initially a tiny bit of thrust loss but we tuned the electric motors to compensate for that.” The earlier designs of the demonstrator had cooling jackets and fins on all six arms, but the company found it could save 250 g of aircraft weight by removing four of them, while keeping approximately the same effectiveness of thermal management. De-ionised water usually acts as the coolant, although methanol can be added for operations in sub-zero environments to lower the coolant’s freezing point. Currently, the demonstrator carries a 4.7 litre tank of compressed hydrogen gas, and can also hold up to 2 kg in payload weight within a 15 kg MTOW, with a maximum flight time of 90 minutes. “The core fuel cell technology has remained largely unchanged from last year,” Robinson said. “The most recent major upgrade involved integrating some of our membrane electrode assembly technology into what was previously the overall Protonex system. “Going forward, we’re looking to develop the technology surrounding the fuel cell, such as the tank, the regulator and the refuelling system.” To that end, Ballard also displayed its new refuelling rig, which was custom- designed by UK-based NanoSun as a flow-reducing filling hose to prevent the build-up of heat that typically occurs when hydrogen gas rushes from its storage vessel into a fuel tank. The device gradually fills a 4.7 litre tank over 20 minutes, avoiding any thermal damage to internal components such as the pressure vessel liner or regulator. Hitec showcased the Endurance UAV from Straight Up Imaging, a UAV that the latter company has designed for a range of users including first responders, construction companies and oil & gas surveyors. “The aircraft can carry a 1 lb [454 g] payload for about 40 minutes, which is notably higher than the average,” said Eric Maglio from Hitec. “The power system has been optimised for the size of the Endurance quadcopter. For example, the electric motors and InterDrone 2019 | Show report Unmanned Systems Technology | October/November 2019 The Ballard-BFD H2-6 fuel cell-powered UAV