How to know the est backup time from a UPS?

[Waqas30]

New here, and loving all the information I was able to find here!

I need to buy a UPS that will give me a backup time of minimum 4 hours when running just my Wifi router, I am looking into buying this APC Smart UPS 1500VA, it is expensive and before I buy it I need advice to make sure it will give the desired backup.

I am a novice with electricity figures, my Wifi router is a US Robotics (USR9113) and its adapter says the following:
Pri.: 230V ~ 50Hz 113mA
Sec.: 15V --- 1A 15VA

I was recently tricked into buying a 750VA UPS (Chinese) that had a 9V battery saying that it will give me the desired backup, the battery only lasted me 1 hour.

I will appreciate any and all help!

Adapter image:

 

[WilliamM2]

I have my router, modem, and wireless telephone running off an old Back-Ups 500 with a new battery. It will run for at least 4 hours. 1500 seems like a bit of overkill, an SUA-750 should be more than you need.

 

[Waqas30]

I have my router, modem, and wireless telephone running off an old Back-Ups 500 with a new battery. It will run for at least 4 hours. 1500 seems like a bit of overkill, an SUA-750 should be more than you need.

Thank you for the reply, any estimate on how much backup will a 750 & 1500 be able to give me when using the charger above?

 

[WilliamM2]

You will be drawing less than 26VA, I would think 20 hours for the 750 and 40 hours for the 1500. That's after you minus a 30% for efficiency.

 

[Waqas30]

You will be drawing less than 26VA, I would think 20 hours for the 750 and 40 hours for the 1500. That's after you minus a 30% for efficiency.

Thank you so much for your reply and the estimates. I appreciate it!

 

[VirtualLarry]

You will be drawing less than 26VA, I would think 20 hours for the 750 and 40 hours for the 1500. That's after you minus a 30% for efficiency.

I don't see how you can calculate that, without knowing the Ah of the battery installed into the UPS. The W/VA ratings are the max capacity of the inverter, and have nothing to do with the battery's run-time.

 

[WilliamM2]

It was an estimate, I could be wrong. The SUA-750 has 2 12v 7A batteries, and the 1500 has 2 12v 18A batteries.

His wall wart is drawing a massive 113ma.

 

[13Gigatons]

You might consider buying several cheaper UPS models and keeping them on hand since there is always a chance for it fail at the worst time. Also since it's only a WiFi router you really don't need pure sine wave which are pretty expensive.