UPS buying suggestion

[Frank Leonhardt]

On 16/10/2013 03:43, yudi v wrote:
>> These are very expensive UPS systems when new, but can sometimes be found
>> at school and local government auctions for about 3% of retail price.  The
>> batteries are always bad, but not difficult to replace. Well, the rackmount
>> ones are stuck in with double-sided tape, and take some convincing.  These
>> are standard sealed lead-acid batteries, used for building emergency
>> lights, alarm systems, and well, computer UPSes.
>>
>> Sounds wise but unfortunately I cannot find any used ones.
>
>
>> The Back-UPS units are better than nothing, but avoid the fat power strip
>> style.
>>
> why would you say avoid the fat power strip ones, they are the low end ones
> but they have the standard plugs unlike the more expensive ones.
> I really don't want to spend more than $200 ore even less if possible. My
> server only cost me $500.
>
> As I have mentioned previously someone wants to sell an unwanted APC
> Smart-UPS SC 420VA
> 230V<http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SC420I&total_watts=50&tab=models>,
> they got with their new PC for half price, I am thinking of going for it.
>

At the risk of going off-topic: as Warren has pointed out, not all UPS 
units are the same. In fact, many units calling themselves a UPS are 
actually backup power supplies, which switch over to battery if the 
mains fails. Common usage definitions vary, but to my mind, in USP the 
output should be supplied by the battery all the time, while the mains 
constantly recharges, so there is no switch-over whatsoever. The quality 
of the mains voltage they produce also varies - it might be a pure sine 
wave (as if the mains always was!), or it might be something else. If 
it's going through a switched-mode power supply afterwards I don't see 
this as a big issue - the only thing I'm worried about is whether it 
keeps the computer (HP Microserver - back on topic briefly) running when 
Gonzo does something to the mains. Audio amplifiers and radio equipment 
might be another matter, but the switcher found in practically every 
computer does such unspeakable things to the input mains anyway I can't 
get to excited about how close to a sine wave the output actually is.

Regards, Frank.