Fiber optic sensors for diagnosis and maintenance in lead-acid batteries

This paper presents a fiber optic sensor for use in battery maintenance and also useful in determining the battery State of Health (SoH). The sensor was originally developed for electrolyte density measurements; the sensor comprises several plastic optical fiber sensors which measure the density of the electrolyte at different heights within the vessel of the battery. The sensor is based on light loss that occurs in the detection zone by means of the variation of the density of the electrolyte. This variation depends on the state of charge (SoC) of the battery at the height at which the sensor is placed and also depends on wear-out of battery. In summary, changes in the density of the electrolyte over time are an indicator of SoH. Strategic positioning of the measuring points of the sensor also allows measurements of other variables that facilitate maintenance: detection of low level of the electrolyte and the sediment of the active material that settles into space at the bottom of the cell.