UPS battery backups: load, runtime and shutdown

Size both watts and volt-amps

List every device that needs battery power, including the switch or router needed to carry shutdown messages. Check the equipment's actual demand during the work it will do, and keep the total within both the UPS watt limit and its separate volt-amp limit. A computer power supply's maximum rating is not a measurement of its normal draw.

The current US CyberPower CP1000PFCLCD is rated at 1000 VA and 600 W. The reviewed CP1500PFCLCD 1000 W version is rated at 1500 VA and 1000 W. APC BR1500MS2 is also 1500 VA but has a 900 W limit. Matching the VA number alone would miss that difference. None of these output ratings tells you how many minutes the battery will last.

Leave capacity for changing demand and follow the exact model's installation restrictions. CyberPower's manuals exclude high-demand appliances such as space heaters and laser printers from the battery-backed outlets. This category covers US 120 V desktop AC units; check the plug, voltage and model revision before using another region's listing as a substitute.

Compare runtime at the same absolute load

A half-load figure changes meaning with the UPS rating: half of 600 W is 300 W, while half of 1000 W is 500 W. Use the same stated watt load for both candidates and retain the manufacturer's conditions.

• At 100 W, CyberPower's current estimates are 30 minutes for CP1000PFCLCD and 66 minutes for the reviewed CP1500PFCLCD.
• At 200 W, the corresponding estimates are 13.5 and 30.8 minutes.

CyberPower describes these as estimates for fully charged, new batteries under normal conditions. Battery age, charge and environment can change the result; the reviewed explanation does not specify a numeric ambient temperature or load power factor. These figures support a comparison of the manufacturer's estimates, not a promise for an installed NAS or computer.

Choose a shutdown delay that leaves time to finish the stop and retain reserve. If your load differs from a published point, read the manufacturer's calculator at that load or leave the runtime unresolved. Do not scale a runtime in proportion to VA, watts or battery amp-hours. CompareFoundry has not measured these units' runtime.

Count the outlets that stay powered

The reviewed CP1000PFCLCD has five battery-backed outlets and five surge-only outlets. CP1500PFCLCD has six of each; BR1500MS2 has six backed outlets and four surge-only outlets. Their US AC receptacles are NEMA 5-15R. The total socket count does not tell you how many devices will remain powered.

Map each critical device to a battery-backed outlet, then check the space needed by its plug or power adapter. Include networking equipment if another device depends on it for shutdown messages. Surge-only outlets protect against specified surges but do not keep that equipment running through a loss of utility power.

Measure the body, cable exits and ventilation space separately. A manufacturer's shipping dimensions are not the UPS footprint, and the body dimensions alone do not establish an installed fit. BR1500MS2's current manual has inconsistent inch and metric dimensions, so those observations remain unresolved rather than becoming a confident fit recommendation.

Read waveform, regulation and transfer time separately

The reviewed CyberPower units and BR1500MS2 are line-interactive UPS models with sine-wave output on battery. Automatic voltage regulation handles specified input-voltage variation; it does not establish unlimited tolerance or zero interruption during a switch to battery.

CyberPower specifies a typical transfer time of 4 ms for these two models. A typical figure is not a maximum. For BR1500MS2, the live US listing gives 8 ms typical and 10 ms maximum, while its April 2026 manual says 8 ms maximum. We retain that disagreement. A transfer-time label is not proof that every connected power supply will ride through an outage.

Connect a data cable and verify shutdown support

The CyberPower models document a rear USB HID monitoring connection and include a USB A-to-B data cable. Their front USB-A and USB-C sockets are charging outputs. APC's manual likewise distinguishes its supplied USB communication cable at the rear Data Port from its front charging ports. Plugging a NAS into an AC outlet or charging socket does not configure automatic shutdown.

Keep three questions separate: does the UPS manufacturer document a data protocol; does the computer or NAS vendor support that exact UPS and software combination; and has the installed setup completed an outage-and-restart test? A vendor compatibility entry is useful evidence, but it does not test your battery, cables, firmware or shutdown settings. A historical driver report may describe a different revision. An absent listing is unresolved evidence, not proof of incompatibility.

For network management, the reviewed CP1500PFCLCD documents an optional RMCARD205. It is not included in the base purchase. Ethernet surge-protection sockets are a different feature and do not provide that management function. Check the protocol and software support at both ends before buying an accessory.

Our NAS power and graceful-shutdown guide explains USB and network arrangements, protected states, shutdown order and restoration checks. Follow the device and UPS manuals for a controlled test, and repeat the relevant checks after changing the battery, load or settings.

Read the NAS compatibility evidence by model

On 2026-10-03, Synology's UPS compatibility list marked CP1000PFCLCD, CP1500PFCLCD and APC Back-UPS Pro BR1500MS2 as Vendor Recommended. These entries were not labelled Synology-tested. Each inspected detail included DS425+, DS925+ and DS223j, but did not identify the UPS hardware revision, NAS operating-system version or test conditions.

These dated observations help choose what to verify next; they do not establish that a particular installation has completed shutdown and restart. A missing entry leaves support unresolved, rather than proving incompatibility. Confirm the exact delivered UPS, NAS software and connection, then follow the controlled test in the NAS guide.

Match the replacement battery to the delivered unit

User-replaceable does not mean one cartridge fits every device with a similar name. CyberPower lists RB1290 for the reviewed CP1000PFCLCD. Its CP1500PFCLCD documentation maps RB1290X2 to serial numbers beginning CXX and RB1280X2B to CR9, CXF or CQC. Check the label on the delivered unit before ordering a replacement; the shop listing alone cannot reveal its serial prefix.

APC lists APCRBC163 for BR1500MS2. Follow the exact replacement procedure and disposal instructions. Battery condition affects runtime, so a replacement plan and a successful shutdown test matter alongside the initial output rating.

Use the UPS comparison to keep exact US packages, source limitations and manufacturer runtime estimates together. Confirm the selected revision and supplied accessories before ordering.