Bigger UPS - Double uptime?

[george]

My current UPS can hold my computer system up and running for 15 mins when the power goes off. The dealer tells me that a more powerful/expensive UPS can keep the system up longer....

I got this quote from a computer dealer (attached), but it looks to me that a bigger UPS can handle more equpment, but the uptime is nearly the same. Will I be able to double the uptime to 30 mins with a "double so powerful/expensive" UPS?

[Tywais]

The uptime will be based on some percentage of full load. If the load is reduced the uptime will increase but maybe not a linear relationship. Certainly you will get a longer uptime with a larger capacity UPS using the same load but not certain if it will be exactly double. Might be able to get the data sheet for the UPS and they should have a table of load versus uptime.

[lopburi3]

Model SUA 7501 at 750va draw lasts 4.8 mins but SUA15001 at 750va draw lasts 24 minutes.

Model SUA750XL at 750va draw lasts 17.2 minutes but at half power draw, 375va lasts 53 minutes.

So yes; a larger capacity unit should give you a much longer up time.

[Crossy]

Does your current UPS allow the use of an external battery pack (many of the APC ones do), could be a cheaper option than a new UPS.

[Firefoxx]

The UPSs that have more uptime usually have bigger or more batteries... which generally means that the heavier it is, the longer it would last. Of course, you don't need that much for your PC.

An alternative would be to use one UPS for your CPU, and another for everything else. Your monitor, if it's a fairly large CRT, will use pretty much power on its own... and you'd need it in case of a power failure.

The uptime data given by most manufacturers are really guestimates, since you can't really tell how much power you'll actually be using from minute to minute. It varies with CPU usage, efficiency, GPU usage, disk usage, etc. Use them as ballpark figures, no more.

[astral]

If you have ADSL remember to connect your modem/router to the UPS as well.

A UPS with a 70Ah car battery should keep you going for quite some time. It is an option I am looking at that the moment.

[monty]

I've done it before, hook up a 70 Ah car battery to a UPS.

Only thing is, you first have to fully charge the battery with a regular charger, then connect to the UPS. The UPS is designed to charge a small maybe 5Ah battery, not a car battery.

However, if the car battery is fully charged, the UPS will have enough charging capacity to keep it topped of...

Runs my PC and accesories, a small office desk light for over 3 hours!

Again, after a prolongued power cut, you'll have to charge the battery with the car charger...

[elkangorito]

It is worthwhile noting that there are many 'parts' to & functions of a UPS. One of these parts is the battery charger. Also, many manufacturers of small & cheap UPS's will purposely restrict the capabilities of the built-in battery charger, so that you will be forced into buying a bigger (higher kVA) UPS in order to have a longer 'back up' time. 'Back up' time is the amount of time your batteries will safely provide power to the protected load (before 'cutoff voltage' is reached), should the 'normal' electrical supply fail. More expensive UPS's will have current limiting capabilities for it's built-in battery charger, making it more flexible with different quantities AND TYPES of batteries.

For those that suggested that the use of larger batteries on UPS's, which were not designed for the UPS, it is a possible work around BUT, BE VERY CAREFUL. If your 'larger than specified' battery becomes fully or mostly discharged due to a 'normal supply' failure, be sure to disconnect the battery BEFORE the 'normal supply' is reinstated. Failure to do so may damage the UPS as the built-in battery charger MAY NOT be able to handle the greater charge rate demanded by the battery.

Please do not forget that Gel batteries are particularly susceptible to a greatly reduced performance if the ambient temperature is above 25 degrees Celsius. It is advised that these Gel batteries be replaced every 2 years of service. Wet cell batteries (Lead/Acid) batteries are also suceptible to the same temperature limitations but can generally take a little more punishment in this regard. THE AMBIENT TEMPERATURE IN THAILAND IS 35 DEGREES CELSIUS therefore ALL batteries used in Thailand will have a shortened life. Disregard this if the batteries are in a constant environment of 25 degrees Celsius or less.

Edited May 23, 2006 by elkangorito

[astral]

When I mentioned a UPS with a car battery, in a previous post I was not thinking of a standard pc UPS.

Rather a larger more substantial unit.

My electrician brought round an Automatic Voltage Regulator today complete with 100AH battery.

It supplies my needs once switched over, but does not handle the transition, where there is loss of power. It was $80 plus $60 for the battery.

I now have this unit, 2nd hand for $50. Quite big, you can get some idea of scale from the screw driver on top. It is now tucked away in a loft area.

It requires 24V which means 2 batteries at $60 each, but it should provide power (300W) for 7-8 hours.

It has certainly run this evening for 4 hours without a hiccough.

It shows what can be done when necessary.

[elkangorito]

When I mentioned a UPS with a car battery, in a previous post I was not thinking of a standard pc UPS.

Rather a larger more substantial unit.

My electrician brought round an Automatic Voltage Regulator today complete with 100AH battery.

It supplies my needs once switched over, but does not handle the transition, where there is loss of power. It was $80 plus $60 for the battery.

I now have this unit, 2nd hand for $50. Quite big, you can get some idea of scale from the screw driver on top. It is now tucked away in a loft area.

It requires 24V which means 2 batteries at $60 each, but it should provide power (300W) for 7-8 hours.

It has certainly run this evening for 4 hours without a hiccough.

It shows what can be done when necessary.

If it doesn't automatically 'kick in' & supply power when the mains power is lost, it is not a UPS. It sounds like you've got a voltage transverter (changes 24 volts DC to 220 volts AC). Correct me if I'm wrong.

BTW, make sure it is properly earthed.