This paper wishes to contribute to the Technological Innovation System (TIS) literature. More precisely, we study the geographic delineation issue of a focal TIS. In a first part, we discuss the geographic delineation debate in TIS framework, and we explain why co-patents are a good tool for mapping a TIS. Then considering the Fuel Cell Vehicle (FCV) as a focal TIS, we analyse 10 carmakers’ co-patent networks in FCV technologies between 2000 and 2013. Our database includes 3,250 co-patents. First, we build the networks corresponding to the three periods 2000-2004, 2000-2009, and 2000-2013. Second, we measure the nationalization index of their networks. Third, we study with whom they have established formal collaborations. The results show: 1) the internationalization increased slowly during the time span. We observe an extension of the network until 2009 and then, a consolidation trend; 2) the nationalization index is rather strong for 5 carmakers, and very weak for 3 others; 3) carmakers call upon different kinds of partners, located, moreover, in different places. The final section learns the lessons from the empirical study.