The development of tools for examining and predicting battery performance represents a significant challenge for the field of monitoring, as it is dependent on nondestructive evaluation (NDE) techniques to provide key behavior descriptors. As the thermal behavior of a battery impacts its internal chemistry, thermal imaging represents an in operando NDE technique capable of providing valuable information to facilitate an understanding of a battery’s overall electrochemical performance. However, previous attempts to directly link thermal imaging analyses to internal chemistry have—so far—proved challenging due in part to the complexities of the relationships between the thermal and the electrochemical battery behavior. In this article, we propose and describe a more refined approach in which correlation between thermal imaging results and internal battery reactions is first established, providing a foundation for determining descriptors for developing early fault detection. Here, this approach is experimentally validated, through the use of a combination of electrochemical, in operando infrared thermography, and post-mortem analyses, which were undertaken in order to characterize selected lead-acid batteries. These results—and their implications for early fault detection—are discussed, along with the challenges facing in operando battery thermal imaging, laying a foundation for developing the understanding vital to future iterative design improvements.