How to calculate UPS time ?

[jumacao]

For UPS with batteries packs of 5000 VA.

How much the UPS will last for:

1- A PC that consume 280 Watts
2- An instrument that consume 36 Watts

 

[davidbeach]

1. will last less time than 2.

Anything more than that will take a lot more information about your UPS.

 

[sibeen]

jumacao, we would need to know what sort of batteries and how many there are, in the UPS, before even a ball park figure could be given.

 

[rbulsara]

You need to know the battery capacity (AH) at minimum and its discharge curve from the manufacturer that shows how long it will last at what load. That curve is not linear.

5000VA would be the rating of the UPS and UPS info is irrelevant.

Rafiq Bulsara

http://www.srengineersct.com

 

[majesus]

Just to expand on this (like everyone else was saying) you do need to figure out the amount of stored energy available. THe 5000VA is just the power. To throw some numbers out there, say the UPS is a single phase 120V system, thus at 120V, the UPS can deliever 41.67A.

But... the question you need to find out is, how long can the UPS do that? 10min, 30min, etc... That is the energy content.

You say have two loads at a total of 316W. (Assuming they both run continously and at the same time). If you want them to run for an hour, you'll need 316Wh of capacity.

So say you have a battery that is at 12V and say it can discharge 30Ah till "some voltage." That's 360AH. You will have roughly (a ballpark, I didn't account for the UPS efficiency,etc) 1hour and 8 minutes worth of runtime.

Hope that helps.
Maj