Polymethyl methacrylate (PMMA) was used as a host for preparing transparent solid polymer electrolytes (SPEs). Ethylene Carbonate (EC) was added as plasticizer. The salts used were pure Li Imide (LiN(CF3SO2)(2)), pure Li Triflate (LiCF3SO3) and mixtures of the two. The SPEs prepared were amorphous as indicated by X-Ray Diffraction (XRD) measurements. They possessed excellent optical transmission characteristics over the visible wavelength range. The conductivity of the SPE is higher when more amount of Li Imide was used.