Linear Tech demos wireless battery management in BMW i3 ‘concept car’
The wireless BMS concept car, developed by Linear’s design partner LION Smart, combines Linear’s highly accurate battery stack monitors with its SmartMesh wireless mesh networking, replacing the conventional wired connections between the battery packs and the battery management system. The benefits, says Linear, include the potential for improved reliability, lower cost and weight, and reduced wiring complexity for large multicell battery stacks for electric and hybrid/electric vehicles.
The demonstration also uses battery packs from Kreisel Electric, specialists in maximising the performance of 18650 cylindrical cells; the company builds battery packs that are liquid cooled, and heated, with a system integrated with the car’s HVAC system. Optimum charging, the collaborating companies explain, can only take place when the battery pack is at a constant 30C, and heating as well as cooling may be required. The partners claim that given sufficient available power, charging to 80% in 18 minutes is feasible.
Electric and hybrid/electric vehicles must be shown to be both safe and reliable. Linear presents its high voltage battery stack monitors as offering leading accuracy and reliability, enabling battery management systems that maximize battery pack performance and longevity. The LTC6811 is a complete battery measuring device for hybrid/electric vehicles that can measure up to 12 series-connected battery cell voltages with better than 0.04% accuracy. Combining the LTC6811 with Linear’s SmartMesh wireless mesh networking system addresses concerns associated with automotive wiring harnesses and connectors.
From the industrial space, SmartMesh embedded wireless networks deliver >99.999% reliable connectivity in harsh environments by employing path and frequency diversity (mesh operation and channel-hopping). In addition to improving reliability by creating multiple points of redundant connectivity, the wireless mesh network enables additional BMS capability.
Wireless connectivity enables more flexible placement of battery modules, and makes possible the installation of sensors in locations previously unsuitable for a wiring harness. Wireless sensors integrated into the SmartMesh network, such as current and temperature monitors, offer the potential for synchronizing these measurements with cell voltages.
Erik Soule, Vice President, Signal Conditioning Products for Linear Technology, said, “Linear’s innovations in two critical industry leading technologies enables wireless battery management at automotive reliability levels. New designs of electric and hybrid/electric vehicles are increasing rapidly and all of the major automotive manufacturers are searching for ways to improve the performance and reliability of their battery management systems as they move into higher volume production. The wireless BMS concept car, realized through the expertise of LION Smart’s BMS design, showcases our product vision.”
Daniel Quinger, CEO of LION Smart, said, “One of our goals in this ambitious project is to demonstrate the improvement in range and charging time that can be achieved by using the latest technologies in partnership with leading global players. Combining Kreisel Electric’s laser welded 18650 modules with direct liquid cooling and Linear Technology’s SmartMesh IP wireless mesh and the LTC6811 battery monitoring IC, together with LION Smart’s Open BMS, enabled a unique battery system with record breaking charge time of just 15 minutes, an energy capacity of over 55kWh, with a range of over 400km. This represents a truly remarkable accomplishment.”
The wireless BMS concept car, Linear says, shows the promise of wireless technology to significantly improve reliability and simplify the design of automotive battery management systems.
Linear Technology: www.linear.com
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