Subject: Laptop 'puters



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(3559)   Sat 27 Jul 91 22:47                             
By: Terry Olsen
To: Don Kulha

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 QE 2.75 b9 & RA 1.01 2306@
MSGID: 1:125/12 4e309570
Yeah you've probably got something there!  Computer (and all) power 
supplies are not 100% efficient. For example, if we get 60% 
efficiency from a power supply we are doing reasonably well. In 
theory, 80% is achievable..So for 50 watts in (the hard drive you 
mentioned) only 25-30 gets to the drive. And that is probably 
regulated on board so that only 10-15 watts is actually used by the 
integrated circuits and motor. Running batteries (12 volt system) 
it seems possible to bypass all the DC to AC, AC inverter..etc.
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(3567)   Sat 27 Jul 91 23:16                             
By: Terry Olsen
To: Tom Keller

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 QE 2.75 b9 & RA 1.01 2306@
MSGID: 1:125/12 4e309c58
* In a message originally to Don Kulha, Tom Keller said:
TK>Don,
TK> 
TK>    Be damned careful of hooking up your 'puter to a
TK>lead-acid battery!  A so-called "12 volt" lead-acid battery
TK>is actually 13.2 volts at full charge, while a 12 volt ni-cad
TK>is actually 12 volts.
TK> 
TK>    *SOME* circuitry may find that extra 10% of EMF more than
TK>it can handle.  I am thinking in particular of the LCD
TK>display and its associated drivers.   Check this out pretty
TK>carefully before you fry your new toy!
TK>
TK>--- ConfMail V3.31
TK> * Origin: Sonoma Online RFE, Fido V12T/HST/V.32
TK>(707)545-0746 (1:125/7)
I think that's right! Lead-Acids can be as much as 15.5 Volts, 
depending on their design etc.  And there is the potential to make 
a very simple 'power supply' from very few components for computer 
use
I'm thinking of a three terminal, large transistor looking thing 
that accepts +12.2 to +18 on one leg, ground on another leg and 
puts out +12 volts DC on the third leg..these are darn cheap and 
there is probably one in most computers as a final regualtor 
(within the computer case). There is one for +12 and one for +5 in 
my C=64.
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 * Origin: End of the World! Fortuna, CA. HST (707) 725-5785 
(1:125/12)
: 125/12 7 151/1000 1003 223