Systems for filling a gas cylinder

A charging system comprising:

• a storage cylinder configured to supply gas;
• a gas cylinder configured to store gas;
• a pneumatic control manifold (PCM) configured to receive a flow control valve, the PCM fluidly coupling the flow control valve to the storage cylinder and the gas cylinder;
• the flow control valve having:
• a housing defining a cavity therein and a longitudinal axis, the housing having an input port for receiving a gas from the storage cylinder, and an output port for delivering the gas to the gas cylinder;
• the cavity defining a staging area fluidly connected to the input port, a delivery area fluidly connected to the input port, and a pressurization area fluidly connected to a feedback sensing port, the feedback sensing port configured to receive pressurized fluid that is pressurized to a pressure level representative of a pressure level of gas delivered to the gas cylinder (P2) and the input port configured to receive pressurized fluid that is pressurized to a pressure level representative of a pressure level of gas received from the storage cylinder (P1), the cavity lying along the longitudinal axis of the housing with the staging area being between the pressurization area and the delivery area, the staging area, the delivery area, and the pressurization area being coaxial with the longitudinal axis of the housing;
• a piston slidably positioned in a channel, the channel extending through the cavity and along the longitudinal axis of the housing between the pressurization area and the delivery area, a position of the piston changing a rate of flow of gas through the flow control valve, the position of the piston moving in response to a pressure at the feedback sensing port, the piston moving longitudinally within the channel toward the pressurization area to a minimum flow position when P2 is less than P1;
• and
• a control spring within the pressurization area, the control spring engaging the piston and exerting a bias force on the piston to bias the piston toward an open position.