From: andrewkennedy775@gmail.com   
      
   On Monday, July 30, 2018 at 6:41:01 PM UTC-5, Ralph Mowery wrote:   
   > In article <40ce16a5-b9e3-41ff-8be5-b2b8aa861b42@googlegroups.com>,   
   > andrewkennedy775@gmail.com says...   
   > >   
   > > I am looking for a formula for calculating the run time of my APC battery   
   system.   
   > >   
   > > I did a search but what I found required a particular model of apc.   
   > >   
   > > Total watts of computer and monitor is about 120 watts.   
   > >   
   > > Battery in my apc is 12V 18 Ah   
   > >   
   > > Thanks,   
   > >           Andy   
   > >   
   > >   
   >   
   > Simple except for one missing piece of info.  How efficent is the system   
   > ?   
   >   
   > The Ah (amps the battery can put out for one hour).  As Amps and voltage   
   > equals watts, your battery is rated for 12 times 18 or 216 watts for one   
   > hour. So you get 216 devided by 120 or 1.8 hours.  Then multiply by the   
   > efficency (loss of the system) that is unknown, but 50 to 80 percent   
   > would be inthe ball park.  So at 50 % you get half of the 1.8 hours or   
   > .9 hour.   
   >   
   > All that is provided the battery can put out enough current to last that   
   > long.  Often the more current the battery is required to put out, the   
   > less time it will last.   
      
   Thanks.   
      
   It ran for an hour just on the battery backup.   
      
   It said I had around 15 mins left when I went back to A.C. power.   
      
   Andy   
      
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