RTC battery life calculation

Discussion in 'General Electronics Chat' started by jonisonvespa, Feb 6, 2013.

  1. jonisonvespa

    Thread Starter Member

    Mar 25, 2012
    49
    0
    ok

    after getting fantasic advice regarding a selection of the battery for my rtc, i tryed to work out how long my battery would last, could someone please check my maths please

    thanks very much


    my RTC runs at 200n


    1 nano = 0.000 000 001
    200 nano = 0.000 000 200

    Say the Battery is 100ma hour,

    so devide 0.1 by 0.00 000 002 = 500 000 total hrs

    =500 000 devided by 24 hrs in a day = 20833 days or

    57 years,
     
    Last edited: Feb 6, 2013
  2. #12

    Expert

    Nov 30, 2010
    16,252
    6,751
    You slipped a digit. 200 nano is 0.000 000 2

    That's 57 years.
     
  3. JMac3108

    Active Member

    Aug 16, 2010
    349
    66
    As you can see, these calculations ausually end up showing that the shelf-life of the battery is the limiting factor, not its capacity.

    But be aware than in your actual circuit you may have other small leakage paths that draw current in addition to the 200nA from the RTC. For example if you are diode-ORing the battery with another power source to the RTC you may have some leakage through the diode when the other power source is turned off.
     
    bug13 likes this.
  4. jonisonvespa

    Thread Starter Member

    Mar 25, 2012
    49
    0
    yes thanks i saw that after i posted it

    thanks very much, i intend doubling the battery to 200ma

    thanks very much
     
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