So that is a 550va that lasts for about 20min. So then a 1300va would last for around 45min?

http://www.amazon.com/Tripp-Lite-SMART1300LCDT-1300VA-Battery/dp/B00AX9Z7W4/ref=sr_1_184?s=electronics&ie=UTF8&qid=1457455368&sr=1-184&keywords=ups+battery+backup