An organic electro-luminescence device includes a substrate, a hole injection layer disposed on the substrate, an organic layer disposed on the hole injection layer, a buffer layer disposed on the organic layer, and an electron injection layer forming above the buffer layer. One chargedischarge power estimating method incorporates voltage, state-of-charge, power, and current design constraints and works for a user-specified prediction time horizon \u0394t. Therefore, it is possible to stack not only fan-out type chip scale packages, but to also efficiently stack ordinary area array type chip scale packages.