NOVELTY - The system (9) has a specification unit (40) for specifying use condition of a storage battery (201) that includes state of the battery contained in status information showing transition of the state of the battery that influences the performance of the storage battery divided in states of the storage battery. A deterioration factor determination unit (5) determines the deterioration factor that shows the condition of deterioration of the performance in the use condition using performance information showing transition of the performance of the storage battery.    USE - Deterioration factor determination system for use in a deterioration prediction system (claimed) i.e. life expectancy predicting system, for a storage battery e.g. secondary battery such as lithium ion battery, lead acid battery, sodium sulfur battery and nickel-hydrogen battery, in general household application and company. Can also be used for a test battery and a fuel cell.    ADVANTAGE - The deterioration factor determination unit determines the deterioration factor that shows the condition of deterioration of the performance in the use condition using performance information showing transition of the performance of the storage battery, so that the storage batteries other than the storage battery in which deterioration test is implemented are made usable by obtaining the deterioration factor with high prediction accuracy.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a deterioration prediction system    (2) a deterioration factor determination method    (3) a program comprising a set of instructions for executing a deterioration factor determination method.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a storage battery life expectancy predicting system.'(Drawing includes non-English language text)'    Specification part (4)    Deterioration factor determination unit (5)    Deterioration factor determination system (9)    Specification unit (40)    Storage battery (201)