[Tfug] UPS sizing

[johngalt1]

----- Original Message ----- 
From: "Bexley Hall" <>
To: "Tucson Free Unix Group" <tfug at tfug.org>
Sent: Wednesday, December 31, 2008 2:35 PM
Subject: Re: [Tfug] UPS sizing


> Hi, Harry,
>
> --- On Wed, 12/31/08, Harry McGregor <micros> wrote:
>
>> I tend to buy good APC SmartUPS upses, cheap, either used
>> locally, or ebay within the phoenix area.

Great idea. That's what I do.

> WorldCare recycles lots of these, pretty regularly.
> Of course, the batteries are usually toast...  but,
> then again, you *expect* to need new batteries anyway.

Too bad WC doesn't offer these UPSes sans batteries in As Is
condition for people to restore. Guess they have sufficient
funding..

> (I have been tempted to tear some of them open and see
> how hard they are charging/floating the batteries...
> it seems like you should be able to get more than a
> few years out of a set of batteries  :<  I suspect
> they err on the side of charging "quicker" rather than
> "safer"  :<  )

>From the data sheets I have read, the best way to reduce
life is excessive discharge for a UPS application.

>> I have a few spare, if your interested, at a very good
>> price to free up the space, including an APC matrix.
>>
>> For most systems, I use either a smart ups 700 or 1000,
>> and
>> I have a
>> 2200xl that will be going in for the home entertainment
>> setup soon.
>
> I've been looking at smaller units -- 500-600VA.

To me this means cheap unit - low voltage - small SLA pack.
Destined for failure soon.

> With hold
> times just long enough for a quick shutdown.  I had some
> of the beige 1000's (1200's?) but they were still a bit
> too large.

Too large in what way?

> (If I'm going to buy large, then I want to
> be able to use marine batteries in the damn things instead
> of the little/expensive gelled electrolytes!)

I wouldn't try to use wet cell batteries in a UPS designed
to charge SLA batteries. Nor, would I use an automotive
charger on SLA batteries.

>From my interest in Solar Power, consider the following
battery / charging info...

http://www.windsun.com/Batteries/Battery_FAQ.htm#Gelled%20electrolyte

Be sure to see the part about marine batteries.

Warning: I did locate the link using Google by the way...

> How do your loads compare to the sizes of the UPS's
> that you are spec'ing?  Are you specing large for greater
> hold times *or* for higher loads?

Why would you spec large for hold times?. I say buying large
for additional hold time is probably a misapplication. Just
use appropriately sized (WRT power). Then size for runtime
using UPSes with modular connectors (easy to add external
packs) or ones designed for external batteries.

Anecdotally, it seems to me that battery life is much longer
in UPSes with additional storage in parallel and UPSes not
excessively discharged.