SCUs (System Capacitor Units) which are power supplies for backing up data are included in power supply sections of information processing apparatus such as servers.
A SCU is in a charged state during normal operation of a system. Furthermore, when the supply of power to the system is stopped due to a power failure or the like, power is supplied from the SCU to save data stored in a volatile memory, such as a cache memory, in a nonvolatile memory. By doing so, the cache data is conserved.
On the other hand, the SCU secures power for backing up data by utilizing charge and discharge of a condenser (also referred to as a capacitor). As a result, repeating charge and discharge causes degradation. Accordingly, in order to improve reliability, a degraded state is regularly diagnosed.
Formerly the technique of randomly selecting a secondary battery cell column on which a discharge capacity test is to be performed from a battery pack in which a plurality of secondary battery cell columns are connected was proposed as a technique for diagnosing a backup power supply. Furthermore, the technique of separating a redundant secondary battery cell column from a battery pack in which a plurality of secondary battery cell columns are connected and determining a discharge power amount of the separated secondary battery cell column was proposed.    Japanese Laid-open Patent Publication No. 10-2943    Japanese Laid-open Patent Publication No. 07-55901
When a degradation diagnosis of a SCU is performed, a condenser discharges. Accordingly, the amount of power obtained by charging decreases. It takes a certain period to complete charging after the degradation diagnosis. If a power failure or the like occurs in this period, the amount of power may be insufficient for backup. As a result, backup may not be performed normally.
In order to prevent deterioration in reliability caused by lack of the amount of power, for example, the number of condensers may be increased. By doing so, the amount of power which decreases by performing a degradation diagnosis is always secured excessively. However, this causes an increase in the number of condensers included. An increase in the number of condensers leads to an increase in the size of a SCU. An increase in the size of a SCU means an increase in the number of restrictions on the installation of the SCU and an increase in the costs and therefore is undesirable. Even if a battery is used in place of a condenser as an electric accumulator for storing electric charges, the same problem arises.