Prognostication of remaining useful-life for flexible batteries in foldable wearable electronics

Abstract

Electronics is increasingly being used in biometric applications for measurement of blood pressure, pulse-ox, heart rate, and biomarkers in sweat. Wearable applications necessitate the use of power sources in thinner form factors which can perform reliably under the stresses of daily motion while being exposed to body temperatures. Power sources may need instantaneous peak power and may be subjected to repeated charge and discharge cycles during the use-life of wearable electronics. In this paper, the state of art thin battery technologies commercially available have been studied for their survivability under exposure to environmental loads typical of wearable electronics applications. In addition, a solution for prognosticating the capacity degradation and remaining useful life have been developed. The charging and discharging cycles were performed on the flexible battery with a test station. The test station was comprised of a programming source meter, a programmable electronic load and a data logger. All of the test devices were controlled with LabVIEW. The test station also allowed for an input of various charging/ discharging conditions. A 1C CC (constant current) charge and discharge current rate was used in the cycles to accelerate the life test. During the test, flexible batteries were subjected to the thermal stress in an environmental chamber. Once a finite number of cycles had been imposed during the accelerated life test, the battery was cooled down to room temperature. Test results at different temperatures were used to estimate the remaining useful life of the battery using extended kalman filter.