Abstract: A portable flat charger for a cell phone has a flat cell employed as the energy source, and a connector, which has a particular specification to correspond to a charging port of the cell phone, has two electrical wires to respectively connect with a cathode and an anode of the flat cell. A resistor and a diode connected in series are further provided between the anode of the flat cell and the connector, wherein the resistor is used to control the charging current intensity, and the diode is applied to prevent a backflow current from the cell phone to the flat battery when the cell phone is completely charged.