July 2021 - The desire for energy-dense and fast-charged battery technology in consumer electronics, electric vehicle, grid, and aviation applications is pushing the envelope from materials to cell and pack designs. However, some approaches could inherently decrease safety of the battery—thus requiring the development of advanced management and diagnostics. Safety of lithium-ion batteries (LiBs), particularly in multicell configurations, is highly variable and could evolve with use. Existing works primarily focus on cell life and safety diagnostics without considering module and pack-level uncertainties and sometimes imply that cell-level electrochemical diagnostics would work in modules or packs, a naive oversimplification. Using example case studies, we highlight the potential and challenges associated with extending single-cell diagnostics to multiple cells, note the existing gaps, and motivate the research, development, and support communities to devote efforts to fill the gap by developing diagnostics at these levels for current- and future-generation LiBs.