Use UPS battery backup with NVG589 Uverse router, why not?

I have a nvg589 router and it will accept an Arris/Motorola internal battery that is like 40$ on the internet.

I will be moving soon and may not have Uverse where i move, and do not want to waste 40$ on an internal battery that I may not need soon.

I have had 2 power outages in the neighborhood in past 2 weeks, and it is only out for seconds, but it takes the nvg589 router about 4-5 mins to get connected fully back to At&t uverse internet service, and in my job that keeps me off my phone and the internet, which i rely on to telecommute.

What would wrong with getting a Store bought UPS battery backup and plug the nvg589 power into it and when the power goes out the UPS battery unit keeps the unit running, and then no 5 min wait due to a 1 second power outage in the house.

Something like the APC units at any computer store, or other brands, how many watts or amps would i need for the uverse unit to stay up in the event of a 1-2 second outage.

IF the power went out for longer, say 10mins or more, i dont care, i dont use the uverse with voice service so it wont affect my phone service, i use cellular for that.

ideas? 

chris