Production scheduling performance can not only be improved by good algorithms, but also by resource augmentation. This paper studies identical parallel batch machines scheduling to minimize total completion time with machine capacity augmentation. The parallel batch machine can process multiple jobs as a batch simultaneously. We quantitatively analyze the impact of machine capacity augmentation on total completion time for unit processing time. We derive an upper bound and lower bound of the impact ratio. This research provides new insights into production scheduling performance improvement with machine capacity augmentation.