Now showing items 1-13 of 13

  • Battery aging impedance spectroscopy and incremental capacity analysis 

    Ovejas Benedicto, Victòria Júlia; Cuadras Tomàs, Àngel (ZAHNER-elektrik GmbH & Co. KG, 2017)
    Conference report
    Open Access
    We analize electrochemical LiFePO4 cells with impedance spectroscopy and incremental capacity analysis in order to establish a correlation with capacity fade. We found that polarization and diffusion impeances increased ...
  • Battery state of charge determination from heat and entropy measurements 

    Ovejas Benedicto, Victòria Júlia; Cuadras Tomàs, Àngel (2012)
    Conference lecture
    Restricted access - publisher's policy
  • Captació d’energia de l’entorn mitjançant elements piezoelèctrics 

    Ovejas Benedicto, Victòria Júlia (Universitat Politècnica de Catalunya, 2008-05-26)
    Master thesis (pre-Bologna period)
    Open Access
    Cada vegada més s’utilitzen dispositius petits, portàtils i de baix consum energètic. Per exemple, les xarxes de sensors autònoms. Aquestes actualment s’alimenten amb piles o bateries i, per tant, encara no són totalment ...
  • Determination of a System’s Entropy Using Pyroelectric Sensors 

    Cuadras Tomàs, Àngel; Ovejas Benedicto, Victòria Júlia (2015-12)
    Article
    Open Access
    We propose a system for measuring entropy variations, S, in thermal systems using pyroelectric sensors. These sensors convert time-dependent temperature variations into electrical current. Consequently, heat and ...
  • Determination of the state of health of Li-ion batteries : the irreversible entropy production approach 

    Ovejas Benedicto, Victòria Júlia (Universitat Politècnica de Catalunya, 2017-11-24)
    Doctoral thesis
    Open Access
    In recent years, portable applications have experienced an exponential growth and consequently, the demand of batteries has increased accordingly. It is widely known, though, that the performance of batteries decreases ...
  • Entropy as a wear out indicator: The resistor example 

    Cuadras Tomàs, Àngel; Ovejas Benedicto, Victòria Júlia; Quílez Figuerola, Marcos (2013)
    Conference report
    Restricted access - publisher's policy
    In this contribution we aim at proposing entropy measurements in resistive elements to characterize the induced damage due to current and Joule effect dissipation. 0.25 W off the shelf resistors are biased with constant ...
  • Entropy characterisation of overstressed capacitors for lifetime prediction 

    Cuadras Tomàs, Àngel; Romero, Ramón; Ovejas Benedicto, Victòria Júlia (2016-12-30)
    Article
    Open Access
    We propose a method to monitor the ageing and damage of capacitors based on their irreversible entropy generation rate. We overstressed several electrolytic capacitors in the range of 33 µF–100 µF and monitored their entropy ...
  • Impedance characterization of an LCO-NMC/graphite cell: ohmic conduction, SEI transport and charge-transfer phenomenon 

    Ovejas Benedicto, Victòria Júlia; Cuadras Tomàs, Àngel (Multidisciplinary Digital Publishing Institute (MDPI), 2018-09-10)
    Article
    Open Access
    Currently, Li-ion cells are the preferred candidates as energy sources for existing portable applications and for those being developed. Thus, a proper characterization of Li-ion cells is required to optimize their use and ...
  • Irreversible entropy model for damage diagnosis in resistors 

    Cuadras Tomàs, Àngel; Crisóstomo, Javier; Ovejas Benedicto, Victòria Júlia; Quílez Figuerola, Marcos (American Institute of Physics (AIP), 2015-10-28)
    Article
    Open Access
    We propose a method to characterize electrical resistor damage based on entropy measurements. Irreversible entropy and the rate at which it is generated are more convenient parameters than resistance for describing damage ...
  • Pyroelectric sensor for entropy measurements 

    Cuadras Tomàs, Àngel; Ovejas Benedicto, Victòria Júlia (Institute of Electrical and Electronics Engineers (IEEE), 2014)
    Conference report
    Restricted access - publisher's policy
    In this contribution we propose a system to measure entropy fluctuations in thermal systems. The system consist of a pyroelectric sensor and a temperature sensor. The pyroelectric convert thermal variations into electrical ...
  • SoH evaluation of LiFePO4 cells using impedance and thermal measurements 

    Ovejas Benedicto, Victòria Júlia; Cuadras Tomàs, Àngel; Morante Lleonart, Joan Ramon (2014)
    Conference report
    Restricted access - publisher's policy
    LiFePO4 is a promising cathode material used in Li-ion batteries. It offers better cyclability and is safer in terms of thermal runaway than previous LiCoO2 or LiMnO2 cathodes. With new applications as electric vehicles ...
  • Supercapacitor impedance in time and frequency domains 

    Cuadras Tomàs, Àngel; Ovejas Benedicto, Victòria Júlia (IEEE, 2012)
    Conference report
    Restricted access - publisher's policy
    In this contribution we estimate supercapacitor impedance from temporal measurements from two points of view: i) fitting a predefined model to the temporal data and ii) transform time domain analysis to frequency domain ...
  • Thermal analysis of the state of charge of batteries 

    Ovejas Benedicto, Victòria Júlia (Universitat Politècnica de Catalunya, 2010-11-22)
    Master thesis
    Open Access