gem@rellim.com said:

There are two parameters for UPS boxes.  One is the power the electronics can
handle.  The other is the amount of energy the batteries can hold.

I think some of the smaller units have inadequate cooling to run at rated
power for long, but their batteries are small enough so that they run out of
power before the electronics overheats.

--
These are my opinions.  I hate spam.

Actually the larger SmartUPS series can run for hours providing a large enough battery string is available    I have a SmartUPS RM3000 running data rack this has 2 external battery boxes and will run everything for 6 hours.

For TimeNuts applications though I'd recommend a Liebert UPS as this is a 'online' UPS as in input is converted to DC and used to float batteries and drive a power oscillator for a true sine output and in a power interruption there is no transfer time or transients on the output

Content by Scott
Typos by Siri

Yo Hal!

On Fri, 16 Sep 2016 00:50:56 -0700
Hal Murray hmurray@megapathdsl.net wrote:

You can change up the batteries for more runtime, but real cheap UPS
will overheat and die.  They were not designed for steady state
operation.

That is the problem with the cheaper APC.  They were designed for 5 or
10 mins at max power.  Run them for two hours at max power then they
overheat and permanently fail.

Nothing to do with size.  I have seen this in big and small.

The other thing is whether there is a transfer switch, or the UPS is on
continuously.  The APC tend to switch the batteries and DC/AC converter
online only when needed.  OTOH, the CyberPower run from the batteries
all the time.  The transfer glitch can be quite large and affect the
load.  So the float type UPS tends to give smoother power more of the
time.

RGDS
GARY

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com  Tel:+1 541 382 8588

Hi

Any time you get into UPS designs, they are all over the map …

Certainly some do. The ones I have do not. You take a pretty significant
efficiency hit when you go “full time DC”.

Bob

I have a pair of Liebert GTX2-700RT online UPSes and they work well; I
just replaced the batteries, lubricated the fans, and cleaned the dust
out of them a couple weeks ago.  They have that sort of standard 4
prong socket on the back for external batteries.

But unlike my two Powerware Prestige EXT UPSes, they only operate with
batteries installed.  The Prestige EXT will operate as a super power
conditioner without batteries which is just as well since it uses 5 x
12V 4AH batteries for 60 volts instead of the more standard and less
expensive 4 x 12V 7AH-9AH batteries.  These have a 4 pin Molex type of
socket on the back for battery expansion.  I have considered
converting these to use a bank of supercapacitors but I suspect the
charge circuit would have a fit charging them from zero volts.

I picked these up inexpensively from http://www.refurbups.com/ but I
have not seen any deals on refurbished online UPSes there for quite a
while now.

If your equipment can run on 12 volts DC, then there are less
expensive solutions like one of those Belkin 12 volt battery backed up
power supplies that some ISPs issue to their customers or something
home grown.

On Fri, 16 Sep 2016 04:56:35 -0400, you wrote: