Apparatus for assembling battery cells or battery modules

Described herein is an apparatus (1) for assembling together battery cells or battery modules having electrical terminals (T) that must be subjected to a welding operation. The apparatus (1) comprises a tool (4) for engaging and holding the elements to be welded, which is movable along at least two axes to carry and hold one or more battery cells (C) or battery modules in a configuration and/or position suitable for welding electrical terminals (T) to respective electrical connection elements (B) and/or suitable for welding said electrical terminals (T) to each other. The apparatus further comprises a welding head (10) carried by said tool (4) and arranged to perform a welding operation on the element to be welded. The tool (4) and the welding head (10) are controlled such that it carries said battery cells (C) or battery modules (M) into said configuration and/or position suitable for performing the welding, and during the performing of the welding, the battery cells (C) or battery modules (M) are welded by