Battery cell monitoring systems comprising a flexible substrate and components integrated onto the flexible substrate, and methods of operating the same are disclosed. The components comprise a computing device and at least one sensor, where the at least one sensor is configured to generate sensor signals indicative of a physical state of the battery cell. The computing device is configured to hold characteristic data values which have been generated based on prior sensor signals. The computing device is configured to receive the sensor signals from the at least one sensor and to generate battery cell status data in dependence on the sensor signals and the characteristic data values.