From: k.nuyt@nospam.demon.nl   
      
   On Sat, 16 Mar 2024 15:27:05 +0000, Mike Scott   
    wrote:   
      
   > ... For my part, and purely to use   
   > as a short-term standby for the Pi until mains resumes or the system can   
   > shut down cleanly   
      
   Please note that the Pi still draws power after shutdown,   
   because it has no power-off circuit of any kind.   
   There is a small but significant stand-by current (not just any   
   LEDs) that will eventually drain the UPS/batteries/whatever.   
   A dumb power source should at least be over-discharge protected   
   (think of protected Lithium batteries) or not be damaged by   
   total discharge.   
      
   Another issue: If grid power is restored before the UPS is   
   empty, the pi will not boot automatically. It only knows how to   
   handle unplug - replug the USB power.   
      
   So a good solution should remove power from the Pi after   
   shutdown, and switch it on again once the grid power is back.   
      
   Like David Higton suggests, MOSFETS are great for that.   
      
   --   
   Regards,   
   Kees Nuyt   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)