Physics based Modeling and Prognostics of Electrolytic Capacitors Chetan S. Kulkarni * Institutefor Software Integrated Systems (ISIS), Vanderbilt University, Nashville, TN, 37235 Jose R. Celaya t SGT In c. , NASA Ames Research Center, Moffett Fi eld, CA , 94035 Gautam Biswas Institutefor Software Int eg rated Systems (ISIS), Vanderbilt University, Nashville, TN, 37235 Kai Goebel § NASA Ames Research Center, Moffett Field, CA, 94035 This paper proposes first principles based modeling and prognostics approach for electrolytic capacitors. Electrolytic capacitors and MOSFETs are the two major components, which cause degradations and failures in DC-DC converters. This type of capacitors are known for its low reliability and frequent breakdown on critical systems like power suppli es of avionics equipment and electrical dri vers of electro-mec hanical actuators. Some of the more prevalent fault effects, such as a ripple vo ltage surge at the power supply output can cause glitches in the GPS po si tion and velocity output, and this, in turn , if not corrected will propagate and dis tort the navigation solution. Prognostics provides a way to assess remaining useful life of a capacitor based on its current state of health and its anticipated future usage and operational conditions. In this paper , we study the effects of accelerated aging due to thermal stress on sets of capacitors. OUf focus is on deriving first principles d eg radation models for thermal stress condition s. The degradation data form the basis for de veloping the model ba se d remaining life prediction algo rithm. Our overall goal is to d er ive accurate models of capacitor degradation, and use them to predict performance changes in DC·DC converters. Nomenclature CR relative dielectric constant EO permitivity of free space V di spersion volume at time t Vo initial electrolyte volume j eo evaporation rate (mg min- 1 area- I) t time in hours P E electrolyte resistivity FE correlation factor related to electrolyte spacer porosity a nd average liquid pathway . We volume of ethyl gl yc ol molecule Vc total capacitor capsule volume de thi ckness of cathode strip C Capacitance ' Gradu ate Research Assistant, Institute for Software Integrated Systems t Research Scientist, Prognostics Center of Excell ence a nd AIAA Member. ! Professor. El ectrical Engineer in g and Computer Science, Institute for Software Integrated Systems § Co-ordinator, Prognos ti cs Center of Exce ll ence a nd AlAA Member. I of 14 American Insti t ut e of Aeronautics and Astronaut ics