Pros: Compact, adequate capacity for light applications, low standby power consumption
Cons: No monitoring port makes this particular model less useful for computer backup.
Cyberpower offers several confusingly similar UPS models which share the same CP425 primary model number. You have to look at the suffix to distinguish them:
- The models with the SL suffix have a serial port for communication with a computer, which is a USB port on the recent units. This is used to tell the computer to shut down before the battery runs out via power monitoring software you run on the computer.
- The models with the G suffix are "Green", in that they have more efficient battery charge maintenance systems that don't waste as much power in normal standby operation.
The CP425 models all have a maximum capacity of 425 Volt-Amps, which translates to a more meaningful 255 watts. This is the maximum power drain it can safely sustain on battery power, if only for a few minutes.
So this particular model has a max capacity of 255 watts, with no communication port, and the more efficient battery maintenance system.
The run-time on battery power depends on the size of the battery (3.0 amp-hours on this model). It is rated to deliver the maximum power of 255 watts for only 2 minutes, or half-power for 7 minutes. This is just enough power to drive a modern desktop computer, and just enough time to shut it down, so the CP425SL and CP425SLG models would qualify for the job of safely shutting down a computer in the event of a power failure. Unfortunately this particular CP425G model doesn't have a communication port, and therefore can't tell a computer to shut down. It's intended more for backing up devices like home video equipment, telephones, or networking equipment to prevent loss of connection or loss of stored information and clock settings in a relatively brief power outage. In that application it can deliver a lower power output for a longer time.
It has 8 widely-spaced power outlets on top, 4 of which have battery backup, and the other four only have surge protection. On the side there's a reset button for the 15-amp circuit breaker, a ground-fault indicator, and in/out telephone jacks to provide surge protection for a telephone line. On top there's an on/off button and a green lamp that glows when the power is turned on. There's no indication of battery charge condition, nor any way to find out on this model.
The transition to battery power is smooth enough not to affect attached electronics when the power fails (4 msec according to the spec). The unit beeps and blinks the lamp once every 30 seconds when it's on battery power. It's not quite as annoyingly loud as my last UPS, but there's no way to shut off the beeping. One minute before automatic shutdown due to low battery power it begins beeping and blinking the lamp rapidly. Then it shuts off and waits for power to be restored. In my test operating network communications gear drawing 15 watts (according to my power meter), it lasted about 55 minutes on a full charge before the low-battery warning soumded.
The time to fully charge the battery is specified as 8 hours. The battery should last 3-5 years before needing replacement. Supposedly the dry lead-acid battery is user-replaceable by opening up the unit, if you can find the right size and if it doesn't cost more than just replacing the unit.
Update: The original battery lasted less than 2 years before it failed to provide power during a brief outage. I replaced it with a larger 5.5 Ah battery since there was room in the case. So far the replacement battery is holding up.