PORTABLE POWER SUPPLY

A portable power supply assembly (100) for power tool, the power supply operated on AC mains having a mains input (201) comprises an AC-to-DC converter (202) coupled between the mains input (201) and a rechargeable battery unit (205), a DC-to-DC converter (204), wherein the rechargeable battery unit (205) couples to an input of the DC-to-DC converter (204), a power inverter (203) for converting direct current (DC) into alternating current (AC), a housing (207) for enclosing the AC-to-DC converter (202), the rechargeable battery unit (205), the DC-to-DC converter (204) and the power inverter (203), an AC outlet (215) disposed on the housing (207). The rechargeable battery unit (205) is connected between the AC-to-DC converter (202) and the power inverter (203), a first-voltage DC power converted from the AC mains via the AC-to-DC converter (202) is stored in the rechargeable battery unit (205), thereby supplies the first-voltage DC power to the power inverter (203) and such that in use, the first-voltage DC power from the rechargeable battery unit (205) is converted to AC output available at the AC outlet (215) of the power supply by the power inverter (203).