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
    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?


  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    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

    AAC Fanatic!

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

    AAC Fanatic!

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