An electrical energy source for an electrically drivable tool containing: a main body, which extends along a longitudinal axis, having a first end and a second end lying opposite the first end with respect to the longitudinal axis； at least one first electrical terminal, which extends away from the first end and has a first diameter； and at least one second electrical terminal, which extends away from the second end and has a second diameter. A voltage is present between the first and second terminals. The first diameter is different from the second diameter. The first electrical terminal extends away from the first end, and the second electrical terminal extends away from the second end of the main body. A tool kit having at least one electrically drivable tool and having at least one electrical energy source and a method for inserting an energy source into an electrically drivable tool.
