A pseudo-chemical equilibrium model has been used to estimate and compare the glass-transition temperatures and ionic conductivities of solid polymer electrolytes (SPEs) made with amorphous aliphatic ether-containing polyethylene carbonate and polyester copolymers. Model parameters were estimated using experimental data from prior studies for three polyethylene carbonate and three polyester copolymer SPEs and then extended to other SPEs within each homologous series. The estimated properties are compared and generally agree with available published experimental data over a range of copolymer compositions with LiFSI and LiTFSI. Simple models using available data for the lithium ion transference number of the polyethylene carbonate copolymer SPEs also were developed. Results from the models are used to estimate and compare the balance of electrical properties for this range SPEs with poly(ethylene oxide) with LiTFSI at low salt concentrations and with polyethylene carbonate with LiFSI at high salt concentrations over a range of temperatures.