This review examines the influence of the various parameters involved in the cast-on-strap (COS) process on the quality of the resulting lug-strap joints. In addition, it provides the findings of an investigation on the macroscopic and microscopic features of COS joints in commercial lead-acid batteries. Some examples of the most common defects that can affect the performance and life of batteries are presented. The nature of the fusion at the lug-strap interface for the various lugs and strap alloy compositions used in conventional, hybrid and valve-regulated lead-acid batteries are also discussed. (C) 2000 Elsevier Science S.A. All rights reserved.