With the widespread use of valve-regulated lead-acid batteries（VRLA） in the DC system of substation

the study on float life of VRLA is of great importance due to uncertainty of its life.In this paper

the floating charge life experiment of VRLA battery combined with electrochemical impedance spectroscopy is conducted in accordance with the actual working condition of VRLA battery in the substation.The measured parameters are analyzed so to find parameter that could reflect the SOH of the battery.It is shown by the result that such electrical parameters as floating charge current

peak and trough voltage as well as variation tendency of electrochemical impedance spectrum（EIS） have a strong correlation with SOH of the battery

which can indicate the capacity decay of VRLA and reduction of remaining life and provide a basis for further state evaluation and life prediction of VRLA.