[Elecraft] Battery Charging with DC Power Supply

[Wes Stewart]

If still functional, the power supply regulator isn't "turned off", it still tries to supply some current* into the (nearly) short circuit SCR.  At the same time the battery supplies current limited only by its internal impedance and the resistance of the interconnect.

* If I'm not mistaken (always a good possibility) the Astrons use foldback current limiting to limit the dissipation of the pass transistors.


--- On Mon, 6/8/09, Ron D'Eau Claire <ron at cobi.biz> wrote:

From: Ron D'Eau Claire <ron at cobi.biz>
Subject: RE: [Elecraft] Battery Charging with DC Power Supply
To: "'Wes Stewart'" <n7ws at yahoo.com>, "'Bill Miner'" <wg6h at yahoo.com>, Elecraft at mailman.qth.net
Date: Monday, June 8, 2009, 9:23 AM




 
 






Tnx Wes!  

   

So the battery voltage across  the power supply terminals
keeps the SCR turned on, even though the supply voltage is turned off by the
crowbar.   

That would surely lead to a dead SCR without a suitable fuse in
the battery circuit.  

   

Ron AC7AC  

   

   

   


 
  
  Since Astron has been mentioned in this thread, I'll use
  that as an example.

  

  The SCR that is part of the crowbar is connected directly across the output
  terminals of the supply.  When used normally, the firing of the SCR
  shorts the output and the supply goes into current limit, if still
  functional, or hopefully blows the primary fuse if not.

  

  With a battery across the output, if the SCR fires, something is going to
  fuse.  It will be either a user-installed external fuse or something
  else.  It would probably not be a good idea to rely on the something
  else.

  

  Wes  N7WS