Laser processing of metallic thin sheets has gained an undoubted industrial interest in the last decade especially due to its implications in the e-mobility field. In particular, dissimilar welding of thin sheets made of different materials, such as aluminum, copper and steel is nowadays recognized as an effective solution for many joining applications in battery and related components production. According to these considerations the present paper is aimed at evaluating the possibility to perform a sound joining of thin copper sheets on thin steel ones in lap-welding configuration. This application is of particular interest especially when cylindrical cells have to be electrically connected to any of the elements constituting the battery, such as printed circuit boards, busbars, etc. By means of a CW fiber laser and a galvo scanner, an experimental campaign was carried out in order to define a process window for characterizing the above-mentioned welding application. The results were characterized by means of metallographic analyses, micro hardness measurements, electrical conductivity tests and SEM-EDS analyses. Particular attention was placed on the role of process parameters in controlling penetration depth on the lower steel layer, since it constitutes the external housing of the single cell and a drop through can seriously damage the cell itself.