Abstract: An apparatus for adding fluids to charged systems includes a cylinder having a first end cap attached to a first end thereof and a second end cap removably attached to a second end thereof. A driving nut is formed at an exterior end of a rod which extends through an aperture of the first end cap and attaches to a piston at an interior end thereof. The piston engages the cylinder to form a variable volume reservoir within the cylinder. A hose assembly extends through the second end cap so as to be in fluid communication with the variable volume reservoir. A handle, or alternatively a power tool socket, may be detachably connected to the driving nut for extending the rod into or retracting the rod out from the cylinder to adjust the variable volume reservoir within the cylinder. The cylinder may be transparent and include graduated markings for determining the amount of fluid within the variable volume reservoir at any given time.