Citation: VARNOSFADERANI, M.A. and STRICKLAND, D., 2017. Online impedance spectroscopy estimation of a dc-dc converter connected battery using an earth leakage monitoring circuit. ABSTRACTElectrochemical Impedance Spectroscopy (EIS) techniques are useful tools for being able to look at the characterisation of batteries under different conditions and/or with different material components. However, EIS analysis is mostly undertaken offline with bespoke equipment. This paper describes a method of undertaking EIS measurement on-line without the use of additional equipment by manipulating the earth leakage monitoring circuit to generate low frequency excitation signals to analyse a battery system connected to a dc/dc converter. This paper describes the methodology and presents some experimental results compared with off line EIS results generated with more traditional EIS equipment under the same conditions to illustrate the concept.