This guide will explain and recommend settings for a NAS connected to a UPS.
You can find the UPS settings under the following path:
Control Panel > Maintenance > Power > Power Management > Minimum UPS Capacity
When you use an Uninterruptible Power Supply (UPS) with a USB connection to the NAS, the NAS shuts itself down, if the UPS’s battery charge gets down to the percentage you specify in this field. This allows the NAS to shut down properly and avoid data loss caused by a power failure when the UPS stops supplying power.
A setting of around 50% is recommended.
A setting close to 100% is not recommended, since it would cause the NAS to shut down whenever the UPS charges.
A setting close to 0% is also not recommended, since the UPS wouldn't have enough power to allow the NAS to shut down properly.