Low-Cost Battery Monitoring by Converter-Based Electrochemical Impedance Spectroscopy

Critical Review of Intelligent Battery Systems: Challenges, Implementation, and Potential for Electric Vehicles

“…This includes, for example, the use of active [296] and passive [143,147,297,298] cell balancers, as well as more advanced methods such as using charging circuits [299,300] or the EV's traction inverter [207]. Switched mode actuators can be further differentiated based on whether the energy used to excite the system is dissipated as heat [301][302][303] or redirected to reduce power dissipation [292,296,304]. The latter is especially relevant for large battery systems, where high currents are necessary to obtain a sufficient voltage response.…”

“…Another challenging aspect of impedance measurement is the design of the Analog Front End (AFE) for data acquisition. Single-ended and differential AFEs comprising fixed or variable gain [292] amplifiers, Lowpass Filters (LPFs) for anti-aliasing, High Pass Filters (HPFs) for removing low frequency and DC components [149,207,291,301], and more advanced circuits are commonly found in the literature. A notable implementation was described by Din et al [296] using a digitally controlled DC servo amplifier for removing DC offsets from the voltage signal to utilize a larger part of the ADC's full-scale range.…”

“…The utilized servo amplifier also features a fourth order active LPF for anti-aliasing. A CSR is most commonly used for current sensing [207,268,296,303,311], but Hall-effect current transducers are utilized as well [112,293,294,301,302]. Low-cost implementations use MCU internal SAR ADCs [157,292,300,301,304] in most cases.…”

“…A CSR is most commonly used for current sensing [207,268,296,303,311], but Hall-effect current transducers are utilized as well [112,293,294,301,302]. Low-cost implementations use MCU internal SAR ADCs [157,292,300,301,304] in most cases. For more performant systems, with an accuracy of >12 bit, standalone SAR or delta-sigma ADCs are employed typically [296,299,[311][312][313].…”

“…After impedance estimation, averaging may be utilized to reduce result variation and allow for more accurate tracking of impedance changes over time [315]. Window averaging [301], exponential averaging [297,306,315], and more advanced methods [305] are proposed in the literature.…”