Linear Technology has showcased a BMW i3 concept car in which the internal communications between battery management PCBs within the main traction battery pack are implemented by wireless links, using at its own Dust Networks 2.4GHz mesh networking.

The wireless BMS concept car, developed by Linear’s design partner LION Smart, combines Linear’s battery stack monitors with its SmartMesh wireless mesh networking, replacing the conventional wired connections between the battery packs and the battery management system. Benefits 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, according to the company.

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 can only take place when the battery pack is at a constant 30°C, 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 synchronising these measurements with cell voltages.