🚀 go-pugleaf

In article <dillon.0p24@overload.Berkeley.CA.US> dillon@overload.Berkeley.CA.US  
(Matthew Dillon) writes:
> >It works, but I have heard a couple of NeXT SEs say that this will
> >void your warranty.  You never know when the diode that prevents
> >reverse current will fail and fry who knows what.
> 
>     IF there is an inline diode there preventing the reverse current it
>     will never fail.  The reverse breakdown voltage for most standard
>     diodes is a hellofalot larger then anything a battery puts out. No
>     current == no heat.  For example, diodes are often used in battery
>     charging circuits like this:
> 
> 	+12V from supply ----*DIODE*----x----> system power
> 					|
> 	+!2V from battery --------------/
> 
>     When AC is available it charges the battery.  When AC is not available
>     the battery does not try to feed the supply, the diode is reverse
>     biased by 12V when the supply DC is at 0V.	This is standard  
operation
>     and the diode will never break down for this case.

Where did you get this dangerous mis-information!!  Do not EVER, repeat, EVER  
attempt to charge a standard lithium cell.  You are looking at a nasty mess at  
BEST, if the seals blow, and a VERY REAL, blow a hole in the board and you,  
explosion if the seals fail to blow.  Lithium cells do not take a joke!

	Now, shorting
>     system power to ground is a different case... in that case the diode is
>     forward biased and dissipates W=Ix0.7 (usually) in heat. Any diode can
>     handle large forward currents for a short while, how long they last
>     depends on their current rating but usually the solder melts on the PC
>     board before the diode dies.  Diodes are usually rated 500mW, 1W, or 5W
>     the smallest being applied to glass diodes.
> 
>     I presume that NeXT is using a similar circuit to power the real time
>     clock and prevent the battery from trying to power the system +5.
> 
Let's hope not!

> 					-Matt
> 
> >MUCH safer to let the capacitor sit and discharge for a few hours on
> >its own.
> >What's your hurry?
> >:-)
> >--
> >David Lemson						     (217) 244-1205
> >University of Illinois NeXT Campus Consultant / CCSO NeXT Lab System Admin
> >Internet : lemson@uiuc.edu		   UUCP :...!uiucuxc!uiucux1!lemson
> >NeXTMail accepted				    BITNET : LEMSON@UIUCVMD
> 
> --
> 
>     Matthew Dillon		dillon@Overload.Berkeley.CA.US
>     1005 Apollo Way		uunet.uu.net!overload!dillon
>     Incline Village, NV. 89451	ham: KC6LVW (no mail drop)
>     USA 			Sandel-Avery Engineering (702)831-8000

(Will this topic ever end?  :-) )  I cannot let dangerous misinformation remain  
as the final word, though.  When it comes to putting batteries in ANYTHING  
backwards, "Just say no!"

Jim