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   comp.sys.raspberry-pi      Raspberry Pi computers & related hardwar      26,127 messages   

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   Message 24,312 of 26,127   
   Vincent Coen to you   
   Backup power supply   
   15 Mar 24 14:10:58   
   
   From: nospam.Vincent.Coen@f1.n250.z2.fidonet.org   
      
   Hello Ahem!   
      
   Friday March 15 2024 10:51, you wrote to me:   
      
    > On Thu, 14 Mar 2024 21:00:49 +1300   
    > nospam.Vincent.Coen@f1.n250.z2.fidonet.org (Vincent Coen) wrote:   
      
    >> Assuming it is fully charged which would be normal (assuming no   
    >> outage in the preceding 2 - 3 hours 95% or better.   
    >>   
    >> Otherwise do you mean the estimated run time if so then system under   
    >> power in watts per   
    >> hour   
      
    >     You have units confusion. Watt is a unit of power, a rate of   
    > movement of energy. Watt-Hours and similar units are units of energy.   
    > Watts per hour is meaningless.   
      
    >> under the rated size - 25%  so lets say :   
      
    >     Assuming you are talking about an APC SMT750I or similar they are   
    > rated for a power output of 750VA or 500W. At full power the battery   
    > is good for about five minutes.   
      
    >> 750 w   
    >> ----  = 150 = long time :)   
    >> 5 w   
      
    >     Make that 5 minutes * 500W/5W or 500 minutes which is indeed a   
    > long time but a lot shorter than the 150 hours you were expecting.   
      
    >> Also e.g., my desktop / server system with an estimated consumption   
    >> of 250w (and it is lower as using modular PSU, 85% eff or better )   
    >> would be around 3 hours but that assumes there is nothing else under   
    >> load and   
      
    >     No it would be maybe 15 minutes.   
      
   The time specified in my post was based on ACTUAL power on time using battery   
   only.   
      
   No I will admit it is also based on some other kit being turned off / shutdown   
   if needed such as the monitor (keyboard / mouse are battery powered).   
   Hub is very low, router low with no secondary kit being connected to the UPS   
   such as printers as not required for normal operation.   
   The primary system uses a modular PSU and secondary DASD are stopped if not   
   use   
   after 2 minutes - they are rarely used other than back ups and secondary   
   systems / O/S, etc.   
      
   Likewise on receipt of a power cut and after a predefined number of minutes   
   not   
   needed applications are shut down although there is no many.   
      
   Average time before the system will shutdown is 75 - 90 minutes on a 1000Kva   
   UPS and with a newish battery.  The UPS is connected directly to supply so is   
   always being under charge or at least being topped up if needed.   
      
   Real live cycle of the UPS battery depends totally on the number of times the   
   UPS is used when the mains power goes down and since moving from a village to   
   town property, power cuts are rare and normally short.   
      
   I do not have a way of working out exactly the power requirements are of the   
   main system although I can look at the loading of the UPS via a direct web   
   location going by memory as it has been years since I tried it and that   
   assumes it was the APC model I currently use as I down sized our UPS's after   
   down sizing our home when the mobo's failed on the 2200Kva units.   
   The cost of the current kit, new, was around 300 each and they have had a   
   least   
   one change of batteries each.   
      
   Not all computer around the house has them such as the media recording system   
   (using MythTV under Ubuntu) does not.   
      
   One powered kit in the village was the C.H. (Gas boiler and controls) but now   
   just use an extension lead to connect it if needed and only in the cold winter   
   period, I seem to recall, maybe once.   
      
   Vincent   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

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