Batch processing is common in mass manufacturing industries due to its high productivity, such as aerospace, semiconductor, and automotive. Based on the analysis of a Bernoulli production line consisting of a discrete machine and a batch machine, this paper investigates a general scenario of batch-batch lines. Utilizing a systems approach with theoretic and experimental analysis, the system properties, such as the monotonicity and reversibility, are analyzed, and the impact of batch size on the performance is studied. Based on them, continuous improvements of the batch-batch lines are explored which include constrained improvement and bottleneck analysis. This paper provides an effective method to analyze batch-batch manufacturing systems, which is also a building block for studying multi-machine systems.