A backpack sprayer system includes a mounting bracket having a battery receiving fixture. A first tank is mounted to the mounting bracket and holds a diluent. A second tank is mounted to the mounting bracket and holds a liquid concentrate. The second tank is selectively, individually removable from the mounting bracket. A mixing manifold is mounted to the mounting bracket and has a first inlet fitting to receive a fixed amount of diluent and a second inlet to receive an adjustable amount of liquid concentrate. The diluent and concentrate are combined to form a mixed solution with the mixing manifold including a mixed solution outlet. A positive displacement pump is mounted to the mounting bracket and has a suction port coupled to the mixed solution outlet and a pressure port coupled with a spray device. A control unit is mounted on the mounting bracket and receives power from the battery.