in the esl the connection extensions 42 extend in a direction from the device body 40 such that an angle is formed between the outer surface of the battery cassette and the connection extensions 42 the angle is preferably with the range of 15 u00b0 to 85 u00b0 in order to ensure contact between the connecting extension and the connecting means of the esl furthermore the angle result in resilient connecting extensions which further improves the accuracy of the contact between the battery cassette and the esl the outer end connecting extensions has a curved shape so that a ridge is formed before the outer end is extending towards the battery cassette this is favourable since the ridges are intended to align the contacting means of the esl while the inwardly curved outer ends of the connecting extensions ensures that connecting extension not will grip the edge of the opening 23 during extraction of the battery cassette from the cavity 22 furthermore two protrusions 43 extend from the device body towards each of the batteries the protrusions 43 are slightly curved upwards to press against the lower circular side 37 of the batteries 35 when the components of the battery cassette are correctly mounted within the cassette and thereby ensure the desired alignment towards the battery the second connecting device 50 is arranged separated from the first connecting device 39 to avoid contact between the first and second connecting device the second connecting device comprises a device body 51 arranged in a recess 44 formed in the first casing section in the same way as the first connecting device from the device body 51 a connection extension.