Subject: Home Computer Power



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(692)   Wed 26 Jun 91 17:41                             
By: Don Kulha
To: Gale Barrows

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    Getting back to your original post Gale....I wanted to dig up 
an article I'd read a short while back for some info for you....It 
was in Home Power Mag #22 (April/May 91)......

> Original Message Date: 16 Jun 91  10:51:48
> From: Gale Barrows
> stated to Teresa, I hope to build a house soon but the REA 
> wants better than $6,000 to bring in the juice. i expect I 
> will be running 12 volt electricicty with a back up 
> generator to run the computer. If there were only a cheap 
> way to run this juice hog off 12 volt, I would be even 
> 
     There are a couple ways to go at running your PC off of 12 
volt power. A while back HP mag ran an article by a fellow who was 
converting IBM PC compatibles to run off of 12v DC. That involved a 
12v monitor and a specially modified power supply. In looking at a 
pinout diagram of the standard IBM type power supply I keep handy 
all the leads are either grounds or +5vdc or +12vdc. I would think 
it not too difficult to to modify or build a power supply to run 
off of 12vdc to supply your computers power needs. Then too this 
chap was modifying/building systems that were 12vdc powered so you 
could always contact him (will either find that back issue or get 
the info from Richard Perez soon). If you aren't running a PC 
compatible I think it would still be a fairly simple matter. I 
believe my old Atari 800 used 9vdc for everything so that would be 
an even simpler hack.
     The article I was looking for was a review of the Powerstar 
series of inverters (Powerstar Products, 10011 North Foothill Blvd, 
Cupertino, CA 95014, (408)973-8502). H-P reviewed their 1,300 watt 
model ($799) and they also offer a 400w ($399) and 700w ($499) 
models. They raved about this product. It was very efficent giving 
efficencys of 98% at 25w (where most inverters of this size are 
about 30% efficient) about 97% at 100w, 89% at 300w,92% at 600w, 
and 94-95% from there on up to it's rated 1300w. I would expect the 
smaller models to offer similar great performance. These inverters 
are also upgradeable, ie., the 400 can be upgraded to 700 which is 
covertable to 1300w which is unique. These are modified sine wave 
inverters using a high frequency (30kHZ) DC to DC switching power 
supply. The high voltage DC is then chopped by field effect 
transistors into modified sine wave 120vAC. The 1300w model is tiny 
because of this and wieghs a mere 5lbs. It is extremely quiet in 
the audio and radio spectrums. Another great thing about it is that 
only consumes 1 watt (yes one) on standby which means that you can 
leave it on all the time without wasting significant power...that 
alone could change the way people use inverters (especially 
considering it's high low load efficency figures). In the test they 
ran all sorts of loads on it, microwaves, shopvacs, satellite TV 
and shortwave systems, lights, wall cube power supplys, etc. all of 
which worked as good or better than they have on other inverters. 
This sounds like a tremendous product.
    The reason I think it would be good for you is that it should 
power your computer system just fine and allow you some other 
120vac luxuries on a regular basis without having to fire off the 
generator. While it's true that running your lighting and other 
appliances directly off of 12vdc bypasses any possible losses from 
the inverter considering the efficencys of the Powerstar units 
inverted power is darn convienient too. It sure would be nice to be 
able to punch the vcr on button and power up the trinitron without 
first cranking the generator or inverter. These small highly 
efficent inverters may hearld a new era of convienience for 
off-grid power generating households.....Check it out!
   P.S.-Gale, you mentioned a generator....hopefully you'll use it 
to charge your batterys and have a solar array (the prices are darn 
reasonable these days) to provide the bulk of your power from a 
renewable resource. Sadly I must admitt to still being a 
"grid-sucker" myself but I'm assembling the tools and knowledge to 
get off the grid and into the country soon. My first step is going 
to be taking this BBS off the grid and we'll progress from 
there....DCK

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