The ageing behavior of lead-acid batteries is very complex, as there are comparatively many different ageing effects. However, the ageing mechanisms in turn have a direct influence on variables that are used for diagnostics. For detailed diagnostics, a precise understanding of the relationship between the progress of individual ageing effects and their impact on the parameters is necessary. In some cases, different ageing effects can also cause opposite changes in the characteristics. Water loss, for example, leads to an increase in acid concentration and thus to a higher OCV, whereas sulphation leads to a decrease in this OCV.
Within the scope of this work, different test routines were initially developed that specifically induce individual ageing mechanisms while minimizing all other ageing mechanisms as far as possible. By measuring the battery characteristics before and after these aging tests, the influence of individual aging mechanisms on the battery characteristics can thus be studied in detail. A special check-up test routine was developed for this purpose, which determines important parameters for diagnostics as e.g. available capacity for different charging strategies, OCV-SOC characteristic as well as internal resistances for low and high current profiles.
We investigated the influence of water loss and ageing mechanisms as corrosion, reversible and irreversible sulphation and shedding on battery characteristics in detail. The conditions of the batteries after ageing were also analyzed by tear down analysis and results of tear down analysis and electrical measurements will be discussed.
The results of this work thus enable a more precise or individual diagnosis of the individual ageing effects.