A 13.56 MHz Multiport-Wireless-Coupled (MWC) Battery Balancer with High Frequency Online Electrochemical Impedance Spectroscopy

This paper presents a multi-MHz multiport-wireless-coupled (MWC) battery balancer with the capability of performing high frequency electrochemical impedance spectroscopy (EIS) to monitor the battery state-of-charge (SOC) and state-of-health (SOH). The proposed MHz MWC architecture performs EIS measurement as well as battery balancing without using extra EIS perturbation circuitry. The battery balancer operates at 13.56 MHz and can perform precise EIS measurement up to 500 kHz. The high switching frequency also eliminates the magnetic core, allowing the utilization of flexible PCB air core magnetics to miniaturize the size of the battery balancer. A 13.56 MHz MWC battery balancer with a four-port air core flexible PCB transformer is built and tested with Lithium-ion, Lithium-polymer and AA-NIMH battery packs. The experimental results matched well with commercial EIS equipment and validated the effectiveness of the MWC battery balancer.