The charge state of the batteries used in mobile devices and electric vehicles cannot be viewed directly. To provide users with most accurate possible information about range and service life, use is still made of complex battery management systems (BMS), but this has the disadvantage that they themselves consume a proportion of what little energy is left. In the SoCUS project, the Fraunhofer Institute for Silicate Research ISC is thus developing a cost-efficient, energy-saving sensor system that can be integrated into the battery and can measure the charge state more reliably than existing methods.

Regular BMS systems calculate the charge state for each battery using the parameters of current and voltage. As the BMS calculations are based on default values, they are prone to error, while frequent partial charging and specific battery types make precise measurement of the charge state more difficult. In contrast, the new method from the Fraunhofer ISC calculates the charge state using ultrasonic pulses. The density of the negative anode - which changes with the battery charge state - is measured and evaluated directly. This delivers a number of benefits - the process is easier and more precise than current technologies and can be integrated into existing systems highly successfully. As one evaluation unit can monitor several batteries simultaneously and continuous monitoring can be dispensed with, this also saves energy and money. Even aging processes can be taken into account more effectively using the new system. The new measuring technology is suitable for virtually all battery types, though it has so far been tested primarily on lithium-ion batteries. As the battery range of electric vehicles remains the key factor for further expanding electromobility, the ability to reliably calculate the battery charge state would be a crucial advantage.

Fraunhofer-Institut für Silicatforschung ISC (97082 Würzburg, Germany)
Website: www.isc.fraunhofer.de