From: whit3rd@gmail.com   
      
   On Sunday, April 21, 2019 at 4:46:59 AM UTC-7, AK wrote:   
   > On Sunday, April 21, 2019 at 5:10:50 AM UTC-5, default wrote:   
   > > On Sat, 20 Apr 2019 20:18:46 -0700 (PDT), AK   
   > >  wrote:   
   > >   
   > > >   
   > > >I have (8) 5 watt leds that are run from a 12VDC source.   
   > > >   
   > > >(3 18650 batteries at 3000 Ma hrs each.   
      
   > I did not see any calculation that determines run time.   
      
   Oh, that's easy; the 18650 batteries are 4V each, so to get 12V you   
   have them in series.   12V * 3000 mAh = energy in the batteries   
   about 36 watt-hours.   So, 7 hours at 5W (one LED), or under an hour   
   with eight at a time.   
      
   That assumes no energy-losing other components (which is unlikely; most   
   LED assemblies for "12V" nominal input have some required ballast resistance.   
      
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