As BMS calculations are based on default values, they are prone to error. Especially with frequent partial charge and certain battery cell types, no precise measurement of the state of charge is possible. In addition, these systems consume some of the energy themselves.
In the SoCUS project, the Fraunhofer R&D Center for Electromobility Bavaria is developing cost-effective sensor systems that can be integrated directly into the battery and can measure the state of charge more accurately than commercially available systems. The systems use ultrasound pulses to measure and evaluate the density of the negative anode which changes with the state of charge of the cell.
The new sensor system is suited for all kinds of battery types but has been especially tested for lithium-ion batteries. Typical fields of application are electric vehicles, stationary storage systems, and drones.
More information: Journal of Power Sources, Volume 343, 1 March 2017: Probing lithium-ion batteries’ state-of-charge using ultrasonic transmission.