Battery backup KDV21

It does have a small battery which is very useful for hunting for the best place and position to locate the device. I doubt that it will operate the device for an extended period of time. You can always plug in the AC adapter into an UPS. 

No luck on power without being plugged in.

Ouch… bad information. Sorry... I had been told there was a battery, but small. Ok, so the external UPS is the way to keep it alive when the power goes out.

The use of an external UPS is a good way to go. If you buy an external UPS consider the brand and size you want. If power loss issues are a consideration using a UPS is a great way to protect your sensitive equipment from power spikes when the power comes back on. The power tends to surge on power lines after an outage and depending upon how far you are from a major transfer station the surge can be hazardous to electronics. We lived in the mountains in CA and power outages were a frequent event. I did have damage to a computer due to a spike so i started running UPS systems in my home to protect my expensive electronics. I found the APC brand to be pretty reliable. Sure you have to replace batteries every 2-3 years but I found it to be a reasonable path. It is sort of like insurance. 

Any idea what battery capacity is needed to run this thing for say 10+ hours?

Specs show:

Adaptador de CA

• 100 V - 240 V
• 12 V/1.2 A

Especificaciones técnicas:

Dimensions 191 (H) x 115 (W) x 120 (D) mm
Weight w/power adapter 1.097 kg
2.412 lb
Operating environment 0 to 40 oC
32 to 104 oF
IoT / GPS Bluetooth 5.1
GPS
Power adapter AC
Power input 100 – 240V, 3A @ DC 15V, 50/60Hz
Theoretical power
consumption
45 W
Wi-Fi connectivity 11ax 4x4 2.4G
11ax 4x4 5G
Roaming continuo
Security WPA/WPA2/WPA3
Buttons Reset (recessed switch)
Arrow Keys (Left & Right)
Enter (aceptar)
Display TFT LCD Non-Touch Panel
2.4 pulgadas
Resolución 240 x 320
Mobile Band 5G NR: n25, n41, n66, n71
4G LTE: B2, B4, B5, B12, B41, B46 (for RX only), B66, B71
Physical Interfaces GE LAN (Yellow)
Ranura para tarjeta SIM (4FF únicamente)
USB tipo C x 1 (fuente de alimentación común)
USB Type C x 1 (Data and other USB Port Purpose

To run say 100 watt delivery with a APC 1500 you would be looking at 30 minutes or so according to what I have seen. My guess is it would take a fairly substantial battery back up to continuously run 45 watt delivery for 10 hours. If only the gateway was being powered it could go for quite some time but I am not sure how long. It may state 45 watt theoretical consumption but if the load was light then the draw would be reduced so it is hard to say. When living in CA in the mountains we left our router on the APC and kept it up and ran the laptops on battery vs. plugging them in. I cannot recall specifics but when the power went out we had LED lamps on APC systems just for such occasions until I had the generator fired up. PG&E power delivery in CA is so unpredictable and poor that living without a generator and transfer box was a bad choice. 

Sure if you have the pockets for a large battery solution and solar then 10 hours would probably be just fine. The primary goal I have had with the APC backup units was to protect my gear from hard shutdown and spikes due to power surge when power inrush on the lines takes place. 

With the 3 APC battery backup units I have I can better protect my computers and audio/video equipment. I would love to have a large battery solution for the home to be able to protect the refrigerator and freezer but dont have the budget for that. Protecting the sensitive electronics with a UPS system is important to me. I prefer the APC UPS systems but I also have a CyberPower UPS. They do have a reasonable guide to selection and how to decide.

https://www.cyberpowersystems.com/blog/buying-guides/choosing-a-ups/