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| Thread ID: 23178 | 2002-08-09 06:31:00 | UPS | Heather P (163) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 69653 | 2002-08-09 07:48:00 | Oh yes. I rang DSE at 5:20 and asked about a UPS. The man with the rather thick accent assured me that they have them in stock - for $40! Now I knew that couldn't be even close so headed for their catalogue. $400 sounded far more plausible. But with that level of knowledge in the store would I ask them for advice?... time to ask on PressF1. |
Heather P (163) | ||
| 69654 | 2002-08-09 07:56:00 | o i forgot to add 500va should be fine for one of your pc's. you might need to get the shutdown pack so you can get the pc to shut down when u r away from pc. have a look around, most new ups have usb connection and shutdown software at no extra charge. |
tweak'e (174) | ||
| 69655 | 2002-08-09 07:59:00 | Actually, addon battery packs don't increase the VA rating. They increase the time you have to take action. The units produce 230V AC at a certain maximum current. That can't be exceeded (by much, anyway). The batteries provide enough stored energy for a certain number of minutes. The batteries are commonly 12, 24, or 36 V, (usually 7Ah ) But the "Ah" is the 20 hr rating If you are pulling a lot of amps, the time is shorter. 5 amps at 230 V will need about 50A at 24 volts. That's why the batteries supply a few minutes. Bigger/Better units use more DC volts, so the Ah's go further. I've got one which uses 16 12V batteries (192 V) . That's why it hasn't had a new set of batteries. :-( |
Graham L (2) | ||
| 69656 | 2002-08-09 08:00:00 | UPS's are either "on-line" or "off-line" types On-line means the PC is always running on the UPS, and the mains are charging the battery. These are more expensive but there is no glitches when power goes off. Off-line types switch in a few milliseconds when supply dips, to the battery sourced supply. In some rare cases the glitch as they switch over can be a problem. As well you have a choice of pure sine-wave, square wave and variations in between with prices to suit. Generally a "modified sine wave" is suitable for PC's, they are not too fussy. As tweak'e has noted, the inrush current of monitors (and PC power supplies) is often too great for them to start, but if already running they will keep going. |
godfather (25) | ||
| 69657 | 2002-08-09 08:03:00 | The battery in most ups units is 12V, same as a car battery, and if you wire one of them into an ups you get about one hours use. This figure of course effected by the size of your system, and the size of the car battery. ... it might sound a bit mickey mouse to some people, but let me assure it works, i've seen it done. I watched an rather innocent sparky spin out when he walked into a room and saw a freind of mine still working on his computer, totally unconcerned about the power being down for ½ an hour! The sparky had never heard of an UPS, it took some explaining. |
Chris Wilson (431) | ||
| 69658 | 2002-08-09 08:12:00 | Thats a good idea Chris. You could get quite a while out of that scheme, cheaply. Just make sure that the UPS is an isolated one, as some cheap ones have little or no isolation between the battery and one side of the 230v, which means the battery terminals could theoretically "float" capacitively to the 230v level relative to the computer case. Nothing to establish an earth reference to. |
godfather (25) | ||
| 69659 | 2002-08-09 09:40:00 | not quite graham. if you check the spec the addon battery pack is a little more than a battery, almost a full ups in itself. however with more normal ups (eg external battery type) you are correct :) mate has his ups running the whole office, kitchen lights and the tv/setero. one day we where wondering why the jug wasn't boiling, then we realised the whole town was with out power(kitchen power points aern't wired to the ups). bugger no coffee :( |
tweak'e (174) | ||
| 69660 | 2002-08-09 09:45:00 | If he'd plugged the jug in, the computer and the rest would have died very quickly. A 1200 W jug will pull about 120A from your battery if you have a 12 V battery UPS. That's why bigger ones use more batteries in series to give 24 or 36 or much more DC volts. | Graham L (2) | ||
| 69661 | 2002-08-09 10:04:00 | There you go Heather. Going by this information, you can get a good cheap UPS by popping in to Repco and picking up a car battery and a set of jumper cables. :D | Elwin Way (229) | ||
| 69662 | 2002-08-09 10:24:00 | exactly graham, thats why the stove and most powerpoints where not wired in. only lights and office power points. it uses 2x24v batteries. last time we had it running it ran for 3 hours with light load (stereo and lights). | tweak'e (174) | ||
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