Abstract
As electric vehicles are gaining increasing worldwide interest, advances in driving range and safety become critical. Modern automotive battery management systems (BMS) compete with challenging performance and safety requirements and need to monitor a large amount of battery parameters. In this paper, we propose power line communications (PLC) for high voltage (HV) traction batteries to reduce the BMS wiring effort. By modeling a small-scale battery pack for frequencies up to 300 MHz, we predict the PLC channel transfer characteristics and validate the results using a PLC hardware demonstrator employing a narrowband single-carrier modulation. The results demonstrate that battery PLC is a demanding task due to low access impedances and cell coupling effects, yet transfer characteristics can be improved by optimal impedance matching. PLC for HV BMS not only saves weight and cost, but also improves flexibility in BMS design. PLC enables single-cell monitoring techniques such as online electrochemical impedance spectroscopy (EIS) without additional wiring. Online EIS can be used for in-situ state and temperature estimation saving extra sensors. This work unveils possible coexistence issues between PLC and battery monitoring. In particular, we demonstrate that certain PLC data or packet rates have to be avoided not to interfere with EIS measurements.
Highlights
Channel modeling or hardware implementation, and a comparison between predicted and actual channel characteristics on an implemented power line communications (PLC) system is missing in literature. We address this issue by developing a novel bottom-up PLC channel model parametrized by high frequency (HF) impedance measurements and 3-D EM simulations on cylindrical 18650 Li-ion cells
Due to the galvanostatic electrochemical impedance spectroscopy (EIS) excitation, both the cell’s voltage response and the applied PLC voltage accumulate and their sum will be measured by the EIS integrated circuit (IC)
We developed a bottom-up PLC channel model that can predict the PLC channel transfer characteristics for both uplink (CMC to battery management unit (BMU)) and downlink (BMU to cell monitoring circuit (CMC)) communication in a smallscale 18650 battery pack
Summary
One of the most essential modules of hybrid and battery electric vehicles (HEVs, BEVs) is the traction battery system. It limits both the power and the mileage of the electric vehicle (EV). As Li-ion batteries are sensitive to misapplications such as over or under voltage, a battery management system (BMS) has to ensure a safe, efficient, and reliable operation [3]. For battery state estimation such as state of charge (SOC) and state of health (SOH), the BMS requires external sensors attached to the cells, which traditionally measure voltage, current, and temperature [4]. The BMS is implemented using a centralized or distributed topology, where the latter can be based on a multi or single-cell approach [5]. The single-cell approach offers the highest battery system modularity and variability and enables advanced single-cell monitoring techniques such
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