n TECHNOLOGY April 2023 www.drivesncontrols.com 30 A GERMAN START-UP has come up with a technology that does away with the need for DC-to-AC converters in battery-powered systems. The “AC battery” system, developed by Munich-based Bavertis, uses electronics to reconfigure battery cells several thousand times per second, and allows the battery to generate AC directly. Usually, battery packs provide fixed DC voltages which need to be converted either to AC, or to lower DC voltages, for most applications. Bavertis’technology generates an AC or DC voltage directly from the battery. Compared to conventional converters, it is claimed to deliver superior AC voltage and current signals (in terms of harmonic distortion) without needing extra filters. The modular design can be used to drive various types of motor, or other AC or DC devices. The technology integrates conventional battery cells with modules containing power electronic switches. The switches allow the modules to be connected either in series or parallel as required – or to be bypassed. Compared to conventional battery packs, in which the cells are connected in a fixed configuration, this flexibility creates redundancy and additional degrees of freedom. In combination with an intelligent operating strategy, the technology can create AC or DC outputs at almost any voltage. External power electronics are not needed, and the cells can be discharged according to their state of charge and age, thus optimising efficiency and service lives. The technology generates constant or dynamic voltage levels by linking small voltages intelligently. This “multi-level” approach has previously been used only for high-voltage applications. But, according to Bavertis, the recent demand for high-power, low-voltage switches for consumer electronics has made semiconductor switches more powerful and affordable, making multi-level inverters practical even for low-voltage applications. The company claims that combining multi-level inverters with state-of-the-art battery technology and AI (artificial intelligence) makes its technology superior to conventional energy storage systems. A battery management system (BMS) monitors and protects the battery constantly. A major challenge with larger battery packs is to balance the various cell capacities, and there are potential problems involving heat dissipation and charging times. Bavertis argues that its ability to control the load on each cell individually overcomes these issues. Using cell-specific load profiles, it can increase the efficiency and lifetimes of storage systems, as well as eliminating the need for an external BMS. The company says that the freedom offered by the multi-level technology, allows it to synchronise energy storage systems with any AC or DC grid in a plug-and-play manner, handling both charging and discharging. Bavertis believes that its technology will allow a “rethink” of battery-based energy storage. “Our goal is to make planes fly, vehicles drive and energy available,” it says. Some of the first applications are likely to be in electric vehicles. Bavertis has linked up with ABT e-Line, a German specialist in alternative EV drives, to develop a battery module which can generate any AC or DC voltage from 3.6–300V directly from a battery. With additional modules, the voltage could be extended up to 1kV. ABT will act as the system integrator. The modular design of the technology will make it possible to power a variety of motors, as well as other AC and DC devices, and to charge the battery from an AC power grid. According to ABT, one advantage of the technology is its high efficiency as a result of producing constantly high DC voltage. Safety is also improved by the ability to intervene actively in individual cells. In the event of a fault, cells can be switched off individually, thus increasing reliability. Other potential attractions for EV applications include faster charging, longer ranges, extended service lives and the ability to re-use battery packs. Bavertis was founded in 2021 by three engineers and a business economist with the aim of making battery systems smarter, more modular and longer-lasting. The company believes that modular, intelligent storage systems can help to supply energy sustainably and efficiently. https://bavertis.com THE CHINESE-AMERICAN robotics developer Flexiv has announced a “revolutionary” robotic gripper that can lift almost anything that fits in its grasp, including oddly shaped items or those with uneven surface textures. Flex says that the Grav gripper, which uses an adhesive material modelled on geckos’ feet, is the next generation of grippers. The gripper incorporates a force-control capability which enables it to sense resistive forces in the sub-gramme region. It can insert micro-components, transfer delicate objects, or be used for machine-tending. The gripper was originally designed to reduce the frequency of end-of-arm tool changes on Flexiv’s Rizon adaptive forcecontrol robots. However, testing with a user who also operated other cobots showed that there was a demand beyond the company’s existing customers. Only minor modifications have been needed to make the gripper compatible with other cobots. “We have been working on the Grav gripper for a while, as we wanted one which utilised the same industrial-grade force control as the Rizon line of adaptive robots,” explains Ryan Coulson, Flexiv’s lead mechatronics engineer. “Not only have we successfully implemented force control, but we have also given the gripper the ability to handle traditionally difficult objects like spheres thanks to the gecko material.” A video of the gripper in action can be seen at https://www.youtube.com/ watch?v=1nqmrDnT16w www.flexiv.com/en Geckos inspire gripper that can grasp almost anything Smart on-battery electronics avoids the need for inverters Bavertis says that its on-battery electronics can generate AC directly at almost any voltage
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