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Replacing a battery with a charged capacitor

  1. Feb 26, 2012 #1
    1. The problem statement, all variables and given/known data
    A Vbatt = 1.5 V battery stores Ubatt = 2.25 kJ of energy. I want to replace this battery with a charged capacitor that stores the same amount of energy and puts out the same voltage. That is, I want a capacitor such that UC = 2.25 kJ and VC = 1.5 V. What must the capacitance of such a capacitor be? What charge must this capacitor hold? Reasonable capacitors typically have a capacitance of at most one farad. Is this capacitor a reasonable replacement for the battery?


    2. Relevant equations
    U=1/2 CV^2


    3. The attempt at a solution
     
  2. jcsd
  3. Feb 26, 2012 #2

    cepheid

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    If you already have the equation for the energy stored in the capacitor, and you know U, and you know V, why can't you just use this equation to solve for C yourself?

    One thing that I've heard is a problem with caps as energy sources is that they discharge too quickly, i.e. you get the energy all at once instead of a little bit at a time as needed.
     
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