11 research outputs found

    State-of-Charge Monitoring and Battery Diagnosis of Different Lithium Ion Chemistries Using Impedance Spectroscopy

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    For lithium iron phosphate batteries (LFP) in aerospace applications, impedance spectroscopy is applicable in the flat region of the voltage-charge curve. The frequency-dependent pseudocapacitance at 0.15 Hz is presented as useful state-of-charge (SOC) and state-of-health (SOH) indicator. For the same battery type, the prediction error of pseudocapacitance is better than 1% for a quadratic calibration curve, and less than 36% for a linear model. An approximately linear correlation between pseudocapacitance and Ah battery capacity is observed as long as overcharge and deep discharge are avoided. We verify the impedance method in comparison to the classical constant-current discharge measurements. In the case of five examined lithium-ion chemistries, the linear trend of impedance and SOC is lost if the slope of the discharge voltage curve versus SOC changes. With nickel manganese cobalt (NMC), high impedance modulus correlates with high SOC above 70%

    State-of-Charge Monitoring and Battery Diagnosis of NiCd Cells Using Impedance Spectroscopy

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    With respect to aeronautical applications, the state-of-charge (SOC) and state-of-health (SOH) of rechargeable nickel–cadmium batteries was investigated with the help of the frequency-dependent reactance Im Z(ω) and the pseudo-capacitance C(ω) in the frequency range between 1 kHz and 0.1 Hz. The method of SOC monitoring using impedance spectroscopy is evaluated with the example of 1.5-year long-term measurements of commercial devices. A linear correlation between voltage and capacitance is observed as long as overcharge and deep discharge are avoided. Pseudo-charge Q(ω) = C(ω)⋅U at 1 Hz with respect to the rated capacity is proposed as a reliable SOH indicator for rapid measurements. The benefit of different evaluation methods and diagram types for impedance data is outlined

    A Novel Evaluation Criterion for the Rapid Estimation of the Overcharge and Deep Discharge of Lithium-Ion Batteries Using Differential Capacity

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    Differential capacity dQ/dU (capacitance) can be used for the instant diagnosis of battery performance in common constant current applications. A novel criterion allows state-of-charge (SOC) and state-of-health (SOH) monitoring of lithium-ion batteries during cycling. Peak values indicate impeding overcharge or deep discharge, while dSOC/dU = dU/dSOC = 1 is close to “full charge” or “empty” and can be used as a marker for SOC = 1 (and SOC = 0) at the instantaneous SOH of the aging battery. Instructions for simple state-of-charge control and fault diagnosis are given

    Differential Capacity as a Tool for SOC and SOH Estimation of Lithium Ion Batteries Using Charge/Discharge Curves, Cyclic Voltammetry, Impedance Spectroscopy, and Heat Events: A Tutorial

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    State-of-charge (SOC) and state-of-health (SOH) of different cell chemistries were investigated using long-time cycle tests. This practical guide illustrates how differential capacity dQ/dU (capacitance) obtained from discharge curves, impedance spectra, and cyclic voltammograms can be used for the instant diagnosis of lithium-ion batteries without fully charging and discharging the cell. The increase of dU/dQ is an early indicator of upcoming heat events and deep discharge. The criterion dQ/dU = dU/dQ = 1 could serve as an indicator for “full charge”. The frequency response of capacitance correlates with the available charge of the battery and reflects overcharge events and deep discharges long before the battery fails. It is not necessary to measure down to extremely low frequencies because the charge transfer pseudocapacitance of around 10 Hz reflects well the SOC. Computer-aided calculation methods for the evaluation of measurements in industrial environments and for the training of students are presented

    Multicenter P300 brain mapping of impaired attention to cues in hyperkinetic children

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    OBJECTIVE: To measure specific neurophysiological attention deficits in children with hyperkinetic disorders (HD; the ICD-10 diagnosis for severe and pervasive attention-deficit/hyperactivity disorder [ADHD]). METHOD: In a multicenter sample of 148 children with HD and control children aged 8 to 14 years, event-related potential maps were recorded during a cued continuous performance test (A-X/O-X). Maps to cues (requiring attention but no response) and distractors and performance were tested for differences between age- and sex-matched HD and control groups (n = 57 each), as well as between clinics (n = 5). RESULTS: The N1, P3a, and P3b maps revealed reliable attention effects, with larger amplitudes after cues than after distractors, and only minor differences across clinics. Children with HD missed more targets, made more false alarms, and had larger N1 followed by smaller P3b amplitudes after cues than did controls. Cue-P3b amplitude correlated with detecting subsequent targets. Cue-P3b tomography indicated posterior sources that were attenuated in children with HD. CONCLUSIONS: Brain mapping indicates that children with HD attend to cues (preceding potential targets) with increased initial orienting (N1) followed by insufficient resource allocation (P3b). These multiple, condition-specific attention deficits in HD within 300 msec extend previous results on ADHD and underline the importance of high temporal resolution in mapping severe attention deficits

    Altered response control and anterior cingulate function in attention-deficit/hyperactivity disorder boys

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    To investigate mechanisms and structures underlying prefrontal response control and inhibition in boys suffering from attention-deficit/hyperactivity disorder (ADHD)

    VLM-1 - Vehicle Design and Analysis (XTRAS-TN-VLM-20150302)

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    This report is a summary of the activities performed by the X-TRAS (Expertise Raumtransportsysteme) group within the German Aerospace Center (DLR) in 2014, based on the data and design created by the VLM-1 development team of DLR and the Brazilian Aerospace Technology and Science Department (DCTA/IAE). The analyses were conducted with the present configuration of the VLM-1 Carrier, which is close to the Preliminary Design Review (PDR) of the Vehicle. VLM-1 is a three-staged solid propellant rocket, capable of scientific suborbital and microsatellite launches. The first two stages feature identical S50 solid rocket motors with thrust vector control and a fixed-nozzle, spin stabilized S44 solid rocket motor in third stage on top. Its maiden flight will take place at Alcantara launch site (Centro de Lançamento de Alcântara) in Brazil. VLM-1 unites flightproven, robust sounding rocket heritage technology and hardware, newly developed motors and structures, and advanced control systems in order to provide efficient launch services. Investigations in this report include, but are not limited to: aerodynamics, trajectory and performance, load analysis, control systems and flight stability, guidance and navigation, mechanical design, separation processes, trust vector control, solid rocket motors, electrical and RF systems, ground infrastructure, fairing separation, launcher testing and qualification, costs, mission cases, and future upgrades; The VLM-1 launcher’s capabilities and system design are described and analyzed in this case study
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