Need to figure out power consumption...

Discussion in 'General Electronics Chat' started by jsmith24, May 18, 2015.

  1. jsmith24

    Thread Starter New Member

    Jul 10, 2013
    16
    0
    Hi all,

    I'm trying to figure out my power consumption so that I can estimate run time for a given battery. Normally this would be pretty straight forward - I'd get a crude estimate by dividing AH by current. However, the current is only a few times per day, as follows:

    Current draw:
    220 mA for 30 seconds per day.
    35 mA for 2 minutes per day.
    3.5 mA for 12 hours per day.
    20 mA for 12 hours per day.

    Battery: 12V, 9AH SLA.

    Can someone help untangle my brain to see the obvious thing that I'm missing?

    Thanks,

    Jack
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,803
    1,105
    As an approximation, ignore the first two quantities. That leaves ~23.5mA x 12 hours, = 0.282AH per day. If you discharge the battery, say, half way (it's bad for the battery to flatten it) you have 4.5Ah capacity; so the life-time would be 4.5/0.282 = ~16 days.
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
    3,250
    626
    I wouldn't run the battery lower than 10.5V. Using SLA 0.05C discharge data and extrapolating; 16-20 days ballpark...
     
  4. paulktreg

    Distinguished Member

    Jun 2, 2008
    612
    120
    Your discharge rate is low and I'd like to increase the bid to 20~25 days.
     
    Last edited: May 18, 2015
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