v8titan
ArboristSite Operative
Actually the chart for the UPS in your link says it will only run his 336 watt load for approximately 6 minutes assuming (min) stands for minutes.
If the OP is planning on going the route of using a stand alone UPS, and I believe most of us agree here that that is the easiest solution, he should first get a unit and make sure it will power the blower motor without overloading the UPS.....checking both startup and extended run. Once he has that part of the equation solved....then he can run the numbers and see what type and how many deep cycle batteries are needed to get the desired standby time.