Uncertainty in the measurement of key battery internal states, such as temperature, impacts our understanding of battery performance, degradation and safety and underpins considerable complexity and cos. ••Systematic and rigorous methodology developed for cell instrumentation.••. EVelectric vehiclesLIBlithium-ion batteriesOCV. Many countries have publicly committed to decarbonise their transport systems between the years 2030–2050. This requirement mandates the electrification of multiple sectors. 2.1. Sensor fabrication and calibrationThermocouple devices were selected as suitable sensor types for internal cell instrumentation. In our research, the developed therm. 3.1. Understanding the instrumented cell performance based on discharge capacityFig. 10 summarises the effect of cell instrumentation on cell performance, in terms of discharg.