Many UPS are started by the electric energy provided by the internal battery. For the UPS that has been placed for too long, the battery self discharge effect and line loss problem often lead to the complete discharge of the UPS power, so that the UPS starting voltage cannot be reached. In this case, you can take out the battery in the UPS for charging, or parallel a battery with the same voltage to the original battery. After the UPS is successfully started, the charging circuit can fully charge the battery to restore to normal. It is a reminder that the battery may be damaged if it is placed for a long time, so the UPS may not be charged regularly when it is not used.