In a message dated 5/8/01 11:44:13 PM GMT Daylight Time, 
travis5765@........... writes:

<< Re: the direct battery powered computer: ............
 
 A computer generally has 4 power sources. +12VDC, -12VDC, +5VDC, and -5VDC. 
 all sources are needed to run the computer.
 >>
Hi Karl and Travis,

What do you think of this idea:

1) buy three 12 volt deep charge RV-marine batteries. 

2) Cut into the middle of the top of one battery to find the lead crossover 
terminal that connects the six 2.1 V individual cells in series (wear eye 
protection in case you accidentally short something out and make fireworks). 
Test the terminal you uncovered with a voltmeter to make sure there is 6.3 V 
to either of the two normal terminals of the battery. If it is the right 
crossover solder a heavy copper wire to it to make it into a center tapped 
12-volt battery that is a dual +6.3 V -6.3 V power supply. Hook a 5V voltage 
regulator to each 6.3 volt leg and now you have the regulated +5V and -5V 
required to run the computer The center tap should go to neutral on the 
computer.

3) Connect the other two 12V batteries in series and their center to neutral 
on the computer. Put a 12V regulator on each 12.6 V (when fully charged) 
battery and you have the plus 12V and minus 12V regulated power required by 
the computer. 

4) Connect three battery chargers, one to each 12V battery. These should be 
the type that automatically shut down so they don't overcharge the batteries. 
I have one from Sears that puts out 5-Amps on the high setting. 

5) Hook a 12V DC/120V AC inverter to any one of the three 12V batteries to 
run your monitor and seismo. Now if the California Independent System 
Operator (ISO), shuts your power grid down your computer and seismo won't 
even know about it and you won't miss that big one. (Murphy's law almost 
guarantees this will happen;-). 

Of course you will need a gasoline or propane powered generator if the ISO 
turns you off for long stretches of time. If you are optimistic about 
California's electrical power problem being solved in the near future don't 
bother getting the generator :-). I live in a rural farm county in New Jersey 
but our power grid gets overloaded too. Another bigger problem we have here 
is ice storms and big wind storms that blow trees down across the power lines 
and leave us without power sometimes for days until the work crews get things 
fixed again. I live on top of a mountain and last summer lightning zapped my 
modem and also the modem in my fax machine despite the power line surge 
protectors that supposedly also protected the phone lines (read the fine 
print on these things and you will see that lighting surges are the one thing 
they don't guarantee to protect you from! ). It cost me ~$150 to have new 
modems installed and if had built the independent battery system described 
above I would have saved the modems (if I had remembered to disconnect the 
phone lines). I welcome your thoughts and comments on the above.

Best regards,
Cap
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