This disclosure relates to a cordless, hand held and electrically powered apparatus, comprising a welding unit (12), a power unit (4) for powering the welding unit, wherein the power unit is connectable directly to and disconnectable from the welding unit via an interface. The power unit is provided with a push button (16) that is configured to energize the welding unit when pressed down, thus initiating operation thereof. The advantage is that the apparatus can be made more compact, and thereby ease of handling is improved. Preferably, the welding unit and the power unit each comprise circuitry (17a, 17b) configured to exchange information when mounted together via the interface. The information is usable for a determination whether the power unit is a correct one or not.