In this paper, the effect of the conductive additive, poly (3, 4-ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT:PSS) on brine water batteries was investigated. Brine water batteries were produced using magnesium powder mixed with aluminum powder, activated carbon and carbon nanotubes, which functioned as the anode with aluminum foil as the current collector. The aluminum current collector also took part in the anodic reaction after the magnesium was used up in the brine water battery reaction. AgCl mixed with activated carbon and carbon nanotubes functioned as the cathode. Platinum mesh was used as current collector for the cathode. The binder used was a mixture of poly vinyl alcohol and poly-acrylic acid. To this binder, the conductive binder PEDOT:PSS was added. The brine water battery consisted of five cells in series connection and each cell had an anode and cathode either with or without PEDOT:PSS. The brine water batteries were operated in a 3.5% NaCl which mimics seawater.