[vox-tech] UPS and auto battery

[Rod Roark]

Interesting stuff.  I never really considered how much
energy a car battery can hold.

Checking my recent electric bills, it looks like my house
uses about 1000 KWH per month when not running the AC
(electric stove, gas heat).  That computes to about 12 amps
average use, so it would seem that with 8-10 batteries and
a hefty inverter I could keep the whole house running for
about 24 hours.  Can that be right?

You mentioned the informative article at
http://www.dansdata.com/diyups.htm.  One thing I don't
understand in there.  The guy says his PC draws about 6 amps
from his battery and the monitor about 8 amps.  That sounds
huge.  He's got a 300 VA inverter and says his PC and monitor
together draw about 70% of its capacity.  Something does not
compute.

-- Rod

On Sunday 07 March 2004 12:37 pm, Ted Deppner wrote:
> On Sun, Mar 07, 2004 at 10:58:21AM -0800, Rod Roark wrote:
> > the inverter, a deep cycle battery and a moderately cheap
> > charger, and keep them on hand but not actually running the
> > computer all the time.
> 
> I have this... a cheap "float charger" can keep a car battery charged
> ($15 or less at Harbor Frieght), or a car charger at $20 to $30.
> 
> > BTW do you know anything about gasoline-powered generators?
> > That may be a more comprehensive solution.
> 
> Don't underestimate a car battery.  Hours of run time.  Really.  And $50
> for hours and hours more (second batter) is possibly cheaper than
> gasoline in a generator.
> 
> I've studied some on generaters, but have no real direct experience.  A
> few items I'd raise though.  Generators can put out square waves or sine
> waves.  On a computer, which their switching power supplies, this
> doesn't make much difference, but sine waves are a lot nicer on
> equipment in the long haul (a CRT is really the more vulnerable thing
> here as compared to a computer).  Generators typically come in two major
> categories, "cheap" ones that have 2 poles and run at 2 times the RPM
> they need to (and thus shorten their life), and better ones that have 4
> poles and run at a nice lower RPM.  (I'm thinking 900/1800 RPM or
> 1800/3600 RPM, but I'm not certain).  A catalog from Northern Tool has
> many choices in it (http://www.northerntool.com/generators/).
> 
> Depending on your needs a $350 to $999 generator might be just fine, but
> if you're interested in long life, and often use, the extra funds on a 4
> pole generator will pay off.  Harbor Frieght has a small but interesting
> looking selection of generators also
> (http://www.harborfreight.com/cpi/ctaf/Category.taf?CategoryID=581).
> More industrial looking than some of the el-cheapo stuff, but caveat
> emptor.
> 
> Extra "features" like built in circuit breakers, low oil shut off, and
> so forth are pretty common everywhere now if you look.  They keep a
> mistake from turning into a big problem.
> 
> Lastly, lower end generators really don't do well with changing loads.
> Ie, if you have 5 computers and a fridge on the generator, expect huge
> voltage swings when the fridge cycles off and on.  This can burn things
> out, and the voltage swings can be normous (burn out lights, blow
> breakers, etc).
> 
> That's the high points from my reading and studies... I'd welcome some
> real world experience from any that have it.  I've spoken with a few
> people "in the boonies" who run off generators routinely for some of
> this.
> 
> -- 
> Ted Deppner
> http://www.deppner.us/