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Xantrex UPS

Tom Metro wrote:
> a typical UPS is designed for short duration use. There
> can't be anything all that magical about these devices - they're just
> trading off VA rating for run time length. You should be able to get the
> same effect by purchasing a UPS with a much higher VA rating than you
> need.

VA rating and runtime length are orthogonal concepts.  Yes, they put
(somewhat) larger batteries into short-runtime high-VA units:  but nowhere
near enough to provide substantially longer runtime for medium-level loads. 
Most of us are looking to put 50 to 300 watts of load onto a unit.  Marketers
try to sell UPS units with higher VA ratings for the same reason you find big
wattage ratings on computer power supplies:  by directing attention to those
ratings, they can offer a cheaper-to-build product but still attract buyers by
touting a headline number.  (I mean, when was the last time you plugged a
thousand watts into a UPS?)

> It'll end up having the same amp-hour rating on the batteries.

If you look inside the Xantrex unit, you find so many batteries that you'll be
convinced.  Buying the batteries alone, if you were trying to build it
yourself, would cost nearly the Best Buy price for this unit.

> That's 2 or 3 times the price of a
> competing 650 VA unit. I'd be curious to know what kind of batteries
> they have inside, and how the run time would compare to a 1000 VA unit
> powering the same 50W load.

Well the factory rating of the internal battery is 40Ah; someone posted a
pretty thorough review at:

The most I've gotten out of a 1000 VA unit from the major brand names
(basically, APC has a lock on most of this market, and I really can't stand
their stuff anymore) is a shade under 2 hours.

Let's take an example:  the APC Back-Ups XS900 available for $119.99 at
MicroCenter (or a steeply-discounted $89.99 if you can still find a non-closed
CompUSA--I'm kinda wondering why MicroCenter is gradually giving up competing
on price lately).  (I chose this example because APC products above 900VA tend
to be priced above the Xantrex.)  One of the first things you notice is the
manufacturer won't even state how many Ah the battery rating is (see  It's
just not in the genes of the marketers at these companies.  But you can do a
Google to find out.  The answer is:  the APC unit contains two 7.5Ah
batteries, total 15Ah--less than half the capacity of the Xantrex.  Well over
half the manufacturing cost of a UPS is the batteries.  That's why I don't
feel that I get my money's worth with these things, except with the Xantrex. 
(Google around to find 40Ah worth of 12-volt sealed lead-acid batteries, I'd
be curious to see what the best price for this commodity is.)

One other note:  UPS batteries don't last forever.  As I discovered this past
week when a cheapo unit from a company called "Newpoint" failed on me only a
year or so after I bought it.

> If long run time is really your goal, you'd be better off using less
> expensive UPSs in conjunction with a gas generator.

Need an automatic transfer switch, electrical permits, new house wiring,
plumbing for another natural gas connection to obtain the same level of
convenience.  (Gasoline-powered generators are a whole 'nother can of worms if
you want to comply properly with fuel storage regulations.)  A $150 UPS unit
that provides hours of runtime is something I think worth considering.


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