CyberPower CP685AVRG review: a small UPS for a modem and router in brownout-prone areas

This is a research-based review, based on manufacturer specs and published data. We do not test products. Figures come from CyberPower's CP685AVRG product page and specifications, checked November 1, 2026, and from the FCC, EPA and Ready.gov sources cited below.

The CP685AVRG sits in the same small-UPS slot as the APC BE600M1, with one meaningful difference. CyberPower lists it as line-interactive with automatic voltage regulation (AVR). When incoming voltage sags, the unit boosts it on its transformer instead of switching to battery. In neighborhoods where storms, heat waves or heavy demand bring dimming lights before an outage, that saves the battery for when it is really needed.

Its battery is a single 12 V, 7 Ah sealed lead-acid block, about 84 Wh nominal. That is enough to keep network gear running through short outages and flickers. It is not enough for a night, and this review explains how to plan around that.

Who should buy it

• Homes with frequent brownouts or voltage swings, where a standby UPS would keep clicking over to battery.
• Anyone who wants the modem, router and VoIP adapter to stay up through flickers without the reboot that follows each one.
• Small spaces: it is 11 × 6.8 × 3.5 inches with keyhole slots for wall mounting.
• Buyers who want the battery under warranty: CyberPower's 3-year warranty includes it.

Who should skip it

• Desktop computers that need sine wave power on battery. The CyberPower CP1500PFCLCD outputs a sine wave in both modes.
• Anyone who needs the internet up through a whole night or several days. A lithium station such as the EcoFlow RIVER 3 Plus holds more than three times the nominal energy.
• Setups with more than four devices to keep powered. Only four outlets are battery-backed.

Strengths

• AVR on a small UPS. CyberPower lists single-boost voltage regulation that corrects minor sags without using the battery.
• 4 ms typical transfer time, faster than the 6 ms APC lists for the BE600M1.
• 3-year warranty including the battery, plus CyberPower's lifetime Connected Equipment Guarantee.
• Four widely spaced outlets for bulky power adapters, so a router brick does not block its neighbor.
• 8-hour typical recharge, shorter than APC's 10 hours for the BE600M1.
• Wall mountable with keyhole slots, and CyberPower lists an ultra-quiet design.

Drawbacks

• Simulated sine wave on battery. Fine for modems, routers and phone adapters with external bricks; not ideal for some computers.
• Four battery-backed outlets. A modem, router, mesh node and VoIP adapter fill them.
• Small battery. 84 Wh nominal, and lead-acid delivers less than its rating at high draw and loses capacity with age.
• No USB charge port. Phones need another source during the outage.

How it compares

The CP685AVRG against APC's small unit, CyberPower's larger sine wave model and a small lithium station. Figures are from each maker's page.

Using it in a long outage

How long it runs network gear

CyberPower's 11 minutes at half load means about 195 W, the load of a small computer. A modem and router are far lighter: label maximums of 20 to 40 W are common, and actual draw is lower. At those loads the battery lasts much longer than the box figure, but how much longer depends on the battery's age and temperature. CyberPower's online runtime calculator gives an estimate for your exact watts. Do not simply divide 84 Wh by your load: lead-acid cells and the inverter both lose energy.

Our router backup guide works the same math for lithium stations: a 286 Wh unit runs a 30 W setup about 8 hours. Use the CP685AVRG for the first minutes of any outage and the flickers in between, and have a larger battery ready for long ones.

Setup routine

1. 01Plug the UPS straight into a wall outlet. Do not daisy-chain it from a surge strip, extension cord or another UPS.
2. 02Put the modem or ONT, router and VoIP adapter on the battery-backed outlets, and printers or speakers on the surge-only side.
3. 03Keep laser printers, space heaters and other high-draw devices off it. CyberPower lists them among devices that void the warranty.
4. 04Once a season, unplug the UPS from the wall for a few minutes, confirm the internet stays up, and listen for the battery-mode alarm.
5. 05Keep phones charged separately, since there is no USB port; see how to charge your phone during a power outage.

Pairing with a power station

If an outage outlasts the battery, plug the UPS into a pure sine power station such as the Jackery Explorer 300 v2 or the Anker SOLIX C1000. The station supplies the hours and the UPS keeps its fast switchover for when grid power returns and drops again.