Introduction / Blah Blah (skip if you want)
Verizon, now Frontier (in my area) rolled out FIOS here over 15 years ago. Since then, it’s been a challenge with battery backup because the ONT is almost always installed at the phone company’s demarcation which is the garage or somewhere else inconvenient.
This is in comparison with the cable company which will usually pay the installer to run the coax to whichever room you want as part of a standard installation.
The garage is hot and not a great place for a UPS because of hot Texas summers that bake the insides of our garage. In the past, I’ve run lengths of extension cord through the attic and into the “computer room” to provide UPS power, but this is not ideal as it violates electrical code.
Extension cords are not allowed to be installed through ceilings, crawlspaces, walls, that sort of thing. The risk of a fire is likely remote if the only thing you are powering is an ONT due to the tiny current draw but it just did not feel right to run that much 120v extension through the attic and through two ceilings.
In my case, I recently moved the “computer room” even further away which was going to force me to either daisy-chain extension cords, put a UPS in a hot garage, or figure out how to steal PoE power from the CAT-6 line that I was already running.
Equipment List
You’ll need at a bare minimum:
- PoE switch or 48v PoE injector that is UPS protected (I am using my existing 48 port Cisco 3750X PoE switch)
- PoE splitter so you can split the power from the data at the ONT (I am using this Linovision PoE splitter /w selectable voltages)
- 5.5mm DC female plug if you are using the Linovision splitter.
- 4.5mm DC female plug for the auxiliary input port of the ONT’s power brick
- A sliver of aluminum foil (!)
I have about 30 years worth of electronics including power bricks, power leads, pigtails, electronics doo-dads, and that sort of thing so I was able to scavenge the needed plug ends from my collection and build a power cable.
Foil Party Trick
By using the aux input port on your ONT’s power brick (in my case, it’s a CyberPower ca25u16v2 power brick), you are basically supplying a secondary source of power that goes to the ONT in the event of a power failure.
Unfortunately, these ONTs will prioritize voice over data during a power outage. During a power outage, you get something like 10 to 15 minutes of data before the data is shut off.
To bypass this restriction, you need to short two pins together to fool the ONT into thinking it is getting full time primary power. Please see the link below.
It’s literally just a sliver of foil that you can jam into the connector. Once you do this, the ONT will accept secondary power without shutting off data after 10 minutes.
I had to do this twice; the first time the foil did not make good contact. The second time proved successful.
You will know if this is NOT successful if the power LED on the ONT flashes when main power is unplugged. It will continue to work but for a limited amount of time before shutting off data. If the power LED remains solid (give it a good 15 seconds to be sure) then you successfully fooled it with the foil bridge.
https://www.instructables.com/I-211M-L-ONT-Enable-Data-While-on-Battery-Power
Selecting The Right Voltage (Voltage Warning)
Depending on your ONT, it may accept as little as 12V or it may require 16V. If you are using a PoE splitter with selectable voltage, you probably don’t have an option for 16V. Pay attention to the data label on the back.
In my case, I have an FRG222 that specifies 16V on its data label. I tried powering it with 12V and the ONT would not take it successfully. Lacking a 16V option on my splitter, I tried it with 18V (thinking that 18V is only a hair more than 16V and the onboard electronics could deal with it). 18V worked fine for me. No ill effects observed.
Do this at your own risk. Try with 12V first before bumping it up to 18V. If you can find a PoE splitter online that supplies 16V, please let us know! The Linovision /w 18v is the closest I could find.
Final Result, Other Methods
The great thing about this method is that it is completely reversible and doesn’t require you butcher the existing power cable.
Other methods I’ve seen discussed involve butchering the proprietary power cable to supply the PoE voltage. That works but you got some ‘splaining to do if you ever have to have a tech visit. This way I can just hide all of my extra “crap” if a tech ever needs to visit for some reason and it never comes up as an issue for him to blame an issue on.
(You can get just the Cyberpower pigtail online if you want, or you can buy a used power brick off of eBay and it should come with the pigtail. Either way will average between $15-$20)
In this photo, you will see a cheap power inverter I bought off of Amazon for about $15. I tried to power the entire unit off of this using 12V of PoE power.
This was not entirely successful; the power brick has a momentary inrush current that exceeds what the PoE splitter is capable of handling. I believe it is associated with the filter caps that are inside the power brick charging up from a resting state. If I quickly unplugged the power brick from outside power and plugged it into the inverter, it would work just fine. I have not observed this behavior of the ONT itself; the ONT can be powered up from a cold discharged state without over-currenting the PoE splitter or PoE port on the switch.