NOK 5G21 Gateway Battery Backup

  • 9 January 2021
  • 42 replies

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42 replies

 The rep thought my device was defective and wanted to send a new one out.  I turned that down.  What good would that do if it’s the same model?


It won’t do any good at all, and you’d be better off buying a stand alone UPS than to expect their device to change. A cheap UPS should be more than enough if it’s only for that, and your other devices use WiFi and are battery powered.



Same issue here!  Just received my device 4 days ago.  The power went out the following day for about 15 minutes and I lost my signal.  Perfect timing!  My friend has the other model (TM-RTL-102) and she does not lose her connection.  When I called to order originally, I verified the battery back up thinking it would be the same as my friend’s device.  Guess I should have phrased the question differently. I called T-Mobile this AM and the rep told me the reason I lose the signal is because of “a lockout in my area”.  I’m baffled by that answer since the manual says the wifi and ethernet will be lost without power.  The rep thought my device was defective and wanted to send a new one out.  I turned that down.  What good would that do if it’s the same model?

It turns out that the battery backup not only won’t keep WiFi or Ethernet connections going, it won’t keep the connection either. In other words, when you get power back it will have to establish a new connection.

Mine was working fine, and after a few weeks without problems, I decided to unplug it and then plug it into a UPS. When it came back up, it wouldn’t get a secondary signal (no 5G). This went on for days, and T-mobile was no help. Rebooting made no difference. Finally, almost a week later, the system  got messed up and the network was unusable. I couldn’t do much other than resetting the device with a pin. After that, it established a connection with 5G, which has been working fine going on two weeks now. It wasn’t a hard reset so it wasn’t a settings issue.

My advice is to plug it into your own UPS and not reboot it or unplug it unless absolutely necessary. Anything I read about location or signal strength was not relevant, because if location had been a problem, it wouldn’t have worked flawlessly for weeks until unplugged without being moved. And it wouldn’t have stayed on 4G until some random event after a reset, and then go back to 5G even though it wasn’t moved.

For those who think that maybe it’s in a borderline area with respect to 5G, my download speeds with 5G are up to 600, usually a bit under 500 being typical, and upload speeds are up to 65, with around 40-50 being typical. And that’s with no data errors when testing. It works great with 5G but will lose its signal even with the battery if not plugged in.

That means, in theory, that the battery serves one purpose, which is to allow you to see signal strength as you move the device around when unplugged.

Spent 2 hours getting to a tech rep who didn’t understand the problem and said it would take “a long time” to get a sup.  Asked for a call back - none. 5 hours later called back and got a rep who said she would connect me- 20 minutes later she connected me back to the original wait que :rage:

So I assume this is still a known issue (lost my internet today briefly during a power failure) - so I was trying to find out if tmo will send a backup battery or if I have to buy my own.

Any help?

Does the battery at least keep the connection from dropping? In other words, if you unplug it for five seconds and plug it back in, will you still be up and running without waiting for anything to restart?

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Update on APC UPS Back-UPS Connect:

After charging for about 10 hours, I was able to stream Netflix movies for over 10 hours. I was hoping for at least 2 hours because that is the longest Zoom meetings that I need to attend from home. 



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Was unsuccessful in finding the price and availability of a Nokia UPS device for this gateway. Therefore, I just bought a generic battery backup on Amazon. 

APC UPS Back-UPS Connect, VoIP, Modem and Router Uninterruptible Power Supply Battery Backup (CP12142LI)

Userlevel 1

It is apparent that there is a UPS connector on the back of the NOK 5g21 gateway that allows for true battery backup. The question now is . . . where can we get or buy this Nokia part?

No UPS or battery back up to the battery from T-Mobile. Battery is to see if the signal is ok, that is it. Why have a battery in it if it only checks signal, when you unplug it, it tells you nothing, even if power outage. It is very confusing. A battery to charge the battery, but that is not included. NO UPS (Uninterruptible Power Supply) from T-Mobile. There, said it twice.

The battery inside the router is so you can move the unit around to find the best cell signal for the router and to remember settings. If you want bttery back up to use if the powder goes out then you can call T-Mobile, they will send you out a UPS battery back up for your router free of charge. The battery back up they send you will run the router for 12 hours.


I was excited to see the back up battery, but it doesn’t allow the unit operting when power is unplugged. What’s the purpose of the back up battery???

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Mine does not lose the custom settings I have set when I unplug the wall wart.  I’ve moved it around to different locations and plugged it back in, no lost settings.  It might have done it once when I first got it, but honestly, I was changing settings like crazy and re-booting so I’m not sure if it did it or I did it.

Oh that's a thought. But who has land lines anymore?! Seems more important to support voice over wifi for emergency calls. Plus the thing has a big 5000mah battery which should be enough to keep WiFi going for several hours! 


Also, is anyone else losing all wifi settings when unplugging?

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Supports the phone jack that is not enabled or used?  Just a thought.  Many of the cable gateways that subscribers have voice service and use a connected “landline” phone use the built in battery to provide a connection when the power goes out.  This supports lifeline and other services.

I also thought the built-in battery would support the gateway cell connection when the AC power was out but like you have discovered it does not.  Disappointed in this. 

Yes, I was trying to move around my house on battery to test 5G signal but then I couldn't log into the thing without wifi! Makes no sense at all. I really thought mine was defective until seeing I'm not alone.

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I was wondering the same thing. The battery would be great for moving your device around the house, checking for the best signal. But soon as you unplug it it shuts off and reboots, when it comes back on it has no wifi or internet connection. It does show Bars, but that’s not alot of help, since there are cell 2 connections

That is correct. I was sold on the idea that it has a battery backup to operate during a power outage.  While the battery has its use it's pretty useless when you can't monitor the signal from the phone application.