50 November/December 2023 | E-Mobility Engineering “Essentially it’s a high-energy density material with a good safety profile – better than NMC – and all the materials in it are low-cost and abundant,” he added. “The challenge at this point is cycle life, but we’re hoping to improve that up to 1000 cycles so we can use it in automotive applications.” Dewesoft demonstrated its Obsidian data logging and DewesoftX processing and visualisation software at the show, running it live hooked up to a QuietKat e-bike and showing the outputs on a dashboard-style display for visitors to interact with. The company makes data acquisition hardware to fit the space available. Mike Davis said, “It could be rugged or nonrugged, for specific uses like measuring power instances, strain or stress. It just depends on what you need to measure. We feed the output into a software suite, where you can visualise the engineering units and make decisions based on what they show.” With the e-bike being tested live on the stand, engineers were invited to walk up and push buttons in an interactive environment they could relate to their own work and try features they might find useful. The e-bike was connected to a sixchannel strain gauge unit that functions as a universal input able to handle any sensor that puts out a voltage signal. The sensors attached to the bike included an accelerometer to measure shock and vibration, a load cell under the seat to measure weight, thermocouples attached to the motor and final drive, and a tachometer putting out a squarewave signal to measure rpm at the wheel and vehicle ‘speed’ on the dyno. Dewesoft describes its Obsidian systems as high-end data loggers and embedded data acquisition systems with low-power ARM processors running Linux-based open architecture operating systems. An Obsidian system is designed to act as a standalone data logger, realtime control system and a signal conditioning front end simultaneously. The company can provide signal amplifier cards for data sources including voltage and current sensors, integrated electronics, piezo-electric devices, thermocouples, resistance temperature detector devices and strain gauges. All Obsidian systems come with the DewesoftX processing and visualisation software, updates for which are free of charge. Hongfa America presented its range of contactors for EV battery packs, the main use for which is making and breaking the connection between the battery and the inverter. These components have been shaped by the growing need to handle much higher voltages and currents, according to Dan Smith. Claiming more than 60% market share in China and 40% globally, Hongfa is also the largest manufacturer of relays in the world. Relays, Smith explained, do essentially the same job as contactors, the distinction between them being roughly the current capacity. Anything less than about 30 A is considered a relay and anything above it a contactor. The engineering challenges involved in handling higher voltages and currents centre on cooling the contactors and arc quenching to protect the main contacts, he said. The main heat source is the I2R relationship between current and resistance across the contacts, with others including the coil that moves the contactors. Cooling techniques centre on sizing busbars for high thermal as well as electrical conductivity, and active cooling measures such as liquid heat exchange. “With the high-voltage systems, there’s a tremendous amount of arc energy available, and if you don’t have a way to push that arc out of the contact area it’ll weld the contacts together,” Smith said. “So we use rare earth permanent magnets to push the arc out of that area and into another part of the contactor assembly.” When the current flows through the magnetic field, the electrons are subject to Lorentz electromagnetic forces that aid in arc suppression, allowing the contacts to close safely. Report | Battery Show North America 2023 Dewesoft’s Obsidian system being put through its paces on an e-bike
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