[Milsurplus] 24V power supply project question

[WA5CAB at cs.com]

Jay,

Further to what George said, we used to use HP lab grade bench supplies to 
charge megabuck silver-zinc battery packs.  After having to pay USIR for 
several, we made up charging cords with a single diode in one of the leads.  If you 
lost power or accidentally unplugged the supply while connected to the battery, 
the battery would eat the output pass element.  So you need to look at the 
output section of each to determine whether it is protected against having full 
voltage applied to the output with AC power removed from the input.  If not or 
if in doubt, simply put a steering diode on all three positive outputs, and 
take your actual output from the common cathodes.  It'll only cost you about 
half a volt.

In a message dated 10/17/2006 3:55:20 PM Central Daylight Time, 
gl4d21a at juno.com writes: 
> If those supplies include current limiting or constant current 
> capabilitites, direct parallel connections should work.  There was a 
> Hewlett Packard Application Note on paralleling regulated supplies 
> published back when they were drawings on cave walls made with a lump 
> of coal which discusses all the parameters.  Simplistically, it goes 
> like this:  Simple paralleling will result in the one supply which 
> has the highest output voltage becoming the primary, and as it 
> reaches current limiting, the output voltage drops a few millivolts 
> and the next starts to pick up part of the load, and so on through 
> however many supplies there are.  Separating the sense connections 
> from the individual outputs is required to make the supplies share 
> the load equally, but you will have to find the App Note to get the 
> details, as all my cave walls got scrubbed clean a few years ago.
> 
> In any event, parallelling supplies, even dissimilar ones requires no 
> magic, just a little understanding of Ohm's and Kirchoff's laws.
> 

Robert Downs - Houston
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