Battery time of a circuit with half-sinusoidal current

Discussion in 'Power Electronics' started by Loreno, Jun 24, 2016.

  1. Loreno

    Thread Starter New Member

    Nov 10, 2014

    I want to calculate how much time will my circuit be able to work on a 9V battery (565mAh), knowing that the current characteristics looks like that:


    The current is show using the green color. It's peak is about 28mA.

    Could you please show me how I can calculate it?
  2. DickCappels


    Aug 21, 2008
    You are probably interested in the average current.

    For a sine wave, average = 0.64 peak. Since you are only using half the cycle, the average current is 0.32 x peak, or 9 ma in your case.

    You can use a discharge curve for the particular type of battery you are using to estimate the battery life.

    The chart below is a sample of a set of discharge curves:
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Bear in mind that it is generally unwise to completely flatten a battery.
    In addition, Murphy's Law dictates that actual battery life is always less than the theoretical value :).
    DickCappels likes this.