The preparation and characterization of a type of ECD which was based on a cathodic EC polymer film, Poly [3, 3-dimethyl-3, 4-dihydro-2H-thieno [3, 4-b][1, 4] dioxepine] (PProDOT-Me2) is reported. A typical device was constructed by sandwiching a gel electrolyte between a PProDOT-Me2 EC film deposited on Indium Tin oxide (ITO) coated glass and a counter electrode which was also ITO glass coated by a Vanadium oxide (V2O5) thin film. The ECD has been characterized. Device contrast ratio, measured as Ε%T, was equal to 60%, and ranged from 2% to 62% between the colored and bleached state measured at 580 nm. A lifetime of over 100,000 cycles between the fully oxidized and fully reduced state has been achieved with only 6% change in the transmittance. The switching speed of a 2.5cm x 2.5cm ECD could be reached in 1 second between the bleached and colored state. The device also has a long open circuit memory. It can remain in the bleached or colored state without being energized for 30 days, and the change in transmittance is less than 6% in colored state. The cyclic voltammetry method was used to detect the moisture content in the gel electrolyte. ECDs of various dimensions were also prepared, 2.5cm x 2.5cm, 7.5cm x 7.5cm, 15cm x 15cm and 30cm x 30cm. The largest scale EC polymer device achieved is 30cm x 30cm. Low sheet resistance ITO glass and a thin-film silver deposition frame were applied to overcome the electric potential drop across the ITO glass surface.