Systems and corresponding methods for optical monitoring of a state of charge or a state of health of a battery are described. For example, the battery monitoring system may include an imaging device that captures images of cells of the battery and determines states of charge of the cells based on observed dimensional changes over time, e.g., relative to reference markers. The observed dimensional changes may also be corrected for dimensional changes due to thermal strain. In addition, states of health of individual cells of the battery may be determined by comparing the dimensional changes of each of the cells over time. Further, the images may be captured at various frequencies, e.g., based on an expected operational duration of the battery and/or based on a current state of charge or state of health.