Backup power requirements?

There are many posts on this, but I haven't found the needed item. I would like to have much more than a few hours' backup power for phone and would like to have internet as well. That means plugging the ONT into a UPS. Question is, how big a UPS? So I'd appreciate knowing how much power the ONT uses when running full phone and internet service (no TV).

Router only uses about 14W, according to Kill-A-Watt, so a regular office UPS will take care of that. And I have a couple of netwbooks with 8-hour batteries. But no idea on the FiOS interface. I could check with the Kill-A-Watt by disconnecting the battery - is that safe for the system? But hoping that someone here will know.

Thanks for your help-

Cten

Accepted answers

jmw1950

Some time ago I measured the wattage on a Motorola ONT/Power supply. Depending upon the state of the battery, 20-25 watts.

So I suspect the smallest UPS you can find will be large enough for the ONT.

However keep in mind that having the ONT up and running for Internet doesn't do you any good if the router isn't powered up, and obviously any devices you may want to use during the power failure will need power.

The battery float charges, so it does use energey at all times, something on the order of 1 watt. Given the size of the battery, you would be unable to distinguish any temperature difference caused by dissipating that 1 watt. Eventually the float charge breaks down the electrolyte in the battery, which is why battery life is limited to about 5 years.

All comments

jmw1950

I have Internet/TV service, but no phone service on ONT. The combination draws 20 watts with the battery fully charged, about 25 wats if the battery needs significant charging. (Measured with a Triplet 9000 series DMM).

I would be surprised if Internet and telephone were any higher. We know that the BBU uses a 7 Ah, 12 volt batter to provide up to 8 hours, so that suggests the actual ONT consumes something on the order of 10 watts for just Telephone service. The power supply is obviously less than 100% efficient, and the battery is subject to constant 'trickle' charge whenever the ONT is AC powered.

So I'd say 20 watts is what you need to power the ONT from an AC outlet.

Two things to be careful of. Switching power supplies are notorious for low power factor operation. That means the actual draw in amps may be substantially higher than the Power ratings would indicate. Your UPS output is rating in VA, not watts.

So while your router may only consume 14 watts, it may be using 25VA, and ONT supply might be using 35VA. So I'd plan my backup time based upon a 60 watt load instead of a 34 watt load. Either way, it isn't going to be much of a load, even on a small UPS.

lasagna

Why would you need to disconnect the battery? Just unplug the BBU (recognizing that you'll take down the phone/TV/Internet) and insert the test meter and let FiOS come back up and online (it will take a minute or so). Same to take the measurement device back out of the path. There is no harm in unplugging the BBU (which is charging the battery and powering the ONT) other than the loss of connectivity while the unit reboots.

tns

@lasagna wrote:
Why would you need to disconnect the battery? Just unplug the BBU (recognizing that you'll take down the phone/TV/Internet) and insert the test meter and let FiOS come back up and online (it will take a minute or so). Same to take the measurement device back out of the path. There is no harm in unplugging the BBU (which is charging the battery and powering the ONT) other than the loss of connectivity while the unit reboots.

You may need to disconnect the battery to make the ONT power down and recycle Unplugging the unit causes the battery to take over powering the ONT although it may take down all but the phone service..

maximuskid3

The battery does not constantly draw power. It doesn't even get warm. Feel it if you don't believe me. Just leave everything as it was and don't concern yourself.

jenifer123

I have no phone and TV for this ONT service; So that I don’t know that how big UPS should be for backup power. But I thing I can say that there is no need to charge phone every time because when it produce heat it get discharged {please keep it relevant}

jmw1950

Some time ago I measured the wattage on a Motorola ONT/Power supply. Depending upon the state of the battery, 20-25 watts.

So I suspect the smallest UPS you can find will be large enough for the ONT.

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