Performing an assessment several years after a system has been installed can be easier if the sysrem has a data logger that has been recording information. If there is no online data logging system, then the data will need to be downloaded from the system’s components using memory cards or via a connected laptop computer. Some system monitors can provide the daily minimum and maximum battery SOC and voltages, and some can tell you how long it has been since the battery was equalized. This information can be helpful in understanding how a system has been operated and also can be used to estimate the remaining life of the battery based on the number of DOD cycles or the cumulative amp-hours that have been removed from the battery over the system’s life