Advice on Battery Backup

[Ronakbhai]

Hello. I'm trying to figure out how to select a battery backup option for my computer. Lately, we've been having loads of power trips where my computer ends up restarting or shutting off.

I do have a Kill-A-Watt meter, and found that my computer uses about 200W at idle, and 550W with graphics cards under load.

So how do I go about selecting a proper battery backup? What I mean, is there a way to calculate with real numbers how long a certain VA and W rated battery backup will last? Say I purchase a 1500VA 900W battery backup, how do I calculate how long my system will run for say at idle?

I'm sure I have loads to read on understanding how Watts and VA relate to actual computer uptime, but if anybody can help guide me in the right direction, I'd be most appreciative. Thanks!

ps - I have read some wikipedia articles, but my physics is very rusty and I find myself going deeper and deeper, rather than making any practical sense of the information. After searching Google relatively extensively, I decided to come here to ask for guidance.

[Delego]

All the stated Values concern Power. What affects how long a battery backup can support your system is the Capacity (Unit: Wh). To run your system one hour on idle you would need 200Wh plus a bit for compensating losses. Formula for needed capacity: (Systems Running Power) * (Time system shall run on battery).

Problem is:
1. Batteries have changing capacities based on their temperature.
2. The capacity for such systems is rarely given.
3. The formula only works if the producer build a system that only runs at the power you need and not on a rather fixed value(which would be really bad).

VA can be kinda ignored, the W of the battery is what should be bigger than your pc under load. VA is the unit for complex power btw.

If you could put in a link, i can probably help you more.

[Nec_V20]

Here's a link to the manufacturer APC and a calculator for what you would need:

http://www.apc.com/tools/ups_selector/index.cfm

[Nec_V20]

A battery backup has one and only one function, which is to allow you to safely down the system, saving or closing any open files in the event of a power cut or a fuse blows.

It is not there to allow you to continue gaming in the hope that the electricity will come back on before your battery runs out.

I have an "APC Back UPS ES8 Power Saving Outlet 700VA (BE700G-UK) UPS". In the event of a power cut the monitoring software will close down my system but the communication hardware is powered by the battery. So even though my electricity may be off I can still use my battery powered netbook to connect to the Internet for quite a long time.

I also have a Wolf 3200W petrol powered backup generator if I really needed to keep my system running for hours or even days. Using a battery backup solution for this purpose is just not cost effective for a normal person.