Abstract This chapter explains fundamental research on fabrication of suitable charge storage devices well integrated into textiles for smart textile systems application. The devices were developed from cotton/polyester fabric as the textile substrate, three different types of conductive yarns as yarn electrodes, and polyethylene dioxythiophene:polystyrene sulfonate (PEDOT:PSS) as the electrolyte. The developed devices are lightweight, flexible, reliable, and well integrated within the textile material. The devices were charged and their discharge recorded in terms of voltage decay. Despite the self-discharge, the devices made with stainless steel yarn electrodes performed better than the ones made with silver-coated and copper-coated yarn electrodes. The charge stored in the devices depended on the charging time to a certain extent. The physics/chemistry behind the charge storage devices is quite complicated. However, the work motivates making of fully integrated electric energy storage in textiles.