NOVELTY - An electrolyte comprises a salt, a solvent, and an indicator. The indicator is present in an amount effective to render the electrolyte visually, olfactorally, or radiatively detectable.    USE - Useful in an electrochemical energy storage device (claimed) or an electrical energy storage device, e.g. a capacitor or a battery e.g. electric vehicles and portable computer or television (TV).    ADVANTAGE - The inventive electrolyte is detectable and distinctive under certain conditions. It can forewarn of a potentially dangerous situation before a failure of the electrolyte occurs.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) an electrochemical energy storage device, comprising: a housing; electrodes in the housing; and the above electrolyte contained in the housing;    (2) a method of preparing the electrolyte, comprising: providing the electrolyte comprising the salt and the solvent; and adding to the electrolyte the indicator in an amount effective to render the electrolyte visually, olfactorally, or radiatively detectable;    (3) a method of manufacturing a system having the electrochemical energy storage device, comprising: providing the electrochemical storage device having the above electrolyte; providing an electronic or electrical system into which the storage device is incorporated; prior to installing the storage device into the system, inspecting the storage device under the conditions where leakage of the electrolyte from the storage device would be detectable via the indicator; and installing a non-leaking storage device into the system; and    (4) a method of detecting the leakage of electrolyte from a battery or capacitor, comprising: providing the electrochemical energy storage device; exposing the storage device to electromagnetic radiation having a frequency in the ultraviolet or infrared ranges; and inspecting the storage device for luminescence.    DESCRIPTION OF DRAWING(S) - The figure shows a voltage window for a TEABF4/PC electrolyte with 1 ppm 1,8-naphthalimide dye.