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Battery Back-Up Systems

Discussion in 'Power Electronics' started by Nic, Nov 3, 2012.

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  1. Nic

    Nic

    2
    0
    Oct 29, 2012
    I have an old battery back-up system for a household computer which uses a 12 Volt battery.

    I want to substitute a 12 Volt deep cycle marine battery and use is as a backup for the electric sump in my basement.

    I'd like some guidance on selecting the correct battery for the job. Since the sump is on a float switch and doesn't run full-time, I thought with the right battery, I might be able to get many hours of battery back up.

    So again; I know that the pump is 9 amps. What else must I take into consideration? If I wanted 24 hours of back up, How do I determine the number of batteries needed?

    How would you approach this project?

    Thank you in advance.
    Nic
     
  2. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    You have to establish an estimated duty cycle of the pump to get a valid backup time...

    For quick and dirty, lets assume stormy weather where the pump will be cycling on/off, so lets say it's on 50% of the time...

    So @ 9A and 50% of the time you have a drain of about 4.5A an hour... Times 24 hours is 108Ah... But, you have to factor in the fact the world is not perfect and thus a 150Ah battery would probably be closer to a real world 24 hour run...

    If the pump is to run 100% of the time you would need a 216Ah (perfect world), and so on and so on...
     
  3. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    651
    May 8, 2012
    I'd advise you to check the specs on your UPS. They come in vastly varying capacities. I doubt that one made for a single PC is up to the task of driving a 9A pump motor. The start current can be over twice its run current. It's also a highly reactive load.

    Chris
     
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