Looks good.

For anyone else out there thinking about doing this...the most dangerous part of this job was soldering those wires onto the batteries. That is about the only dumb thing I see here.

The required heat to get the solder to flow means the batteries get hot. Not typically a good idea to be standing over something you are heating past it's max.

This requires something called a spot welder. Op chose risk over $. It'll be better just just buy a ups if you don't have a spot welder.

Finally made an UPS for my both Router and ONU. Now I'm enjoying internet without interruptions.

Inspiring job. Well done. My mind is blown. Until now, I've never considered making my own UPS.

Something I'm not quite understanding: how does the power get out to the equipment that the UPS is powering? Did you hack together some barrel connector to barrel connector cords; eliminating the need for the router and the ONU's wall warts?

Which part of this is ups circuit? Does it switch over to battery, or load sharing?

How long will it last on that?

APC engineers will be slapping their foreheads on this one :p

Does it have a low voltage disconnect? Because it's not good for batteries to be pulled too low.

I got my DC UPS from AliExpress for not much, but it's interesting to see something handmade.

I also Like DIY but at this time and Age, getting a 30W type C USB-PD charger, 30W Type C USB-PD powerbank, and a type C 12V activator/adapter woukd be My way to do it. Easier to replace by buying an over-the-counter replacement. That way I can also instruct someone else to buy and replace stuff Without me. It gets tiring to fix things yourself because people dont Even recognize basic electronics. And I can use a 15V type c adapter or 5V for other Network equipment Like an Asus router or a low-power tplink switch.

Another way would be a fast enough charger, to a powerbank that can do passthru, and a dual-head 5-to-12V2A adapter.

But still pretty cool. I remember Building a powerbank Full of AAs and a Couple of LM7805 to give 5V2A to My PSP. Good times.

No way is this working as an ups. It may work as a back up for voltage drop, an ups works as a sure protector, monitors incoming voltage, power conditioner and battery back up. 2 12v 7ah is barely enough for a few devices. Most take 4 to handle the wattage. Be safe.

Nice. Which tutorial did you follow? I've seen a few on the web.

I mean, good thought. But you couldn't pay me enough to put this in my home. Former electrical engineer a lifetime ago, this is not safe. At all. A plastic, ungrounded box. You did a good job on the shrink-wrapping, you still have a lot of exposed connections. 15v2a isn't that high, but still a short to ground or a Li-ion battery run off, you're going to have a very bad day.

Wow, I didn’t know 18650s go all the way up to 3800 Mah

Loved it! Is there any similar product commercially available to buy? Any link?

Great idea, unfortunately whenever I lose power, I also lose Internet to my house, so a UPS wouldn't do me any good.

Check out the Pico UPS and other devices they sell. Looks like you've hit all the big parts out- I'd suggest adding some large accumulation caps on the output just to carry over sudden surges but otherwise- AWESOME!

Power outages doesn’t effect the node or central connection for the area ?

Hey mate can u build one for me I’d pay you surly

How long does it last?

Lol I thought these were AA’s at first.

Except when the power goes out so does any ISP's internet. Unless you are satellite?