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Amp hours to Farads conversion

  1. Sep 16, 2008 #1
    I was just curious if it would be possible to make my E-bike run on capacitors instead of Lead acid batteries even if the range was much shorter. So how many Farads would equal 1 Amp hour? At 12v lets say for now. Thanks!
  2. jcsd
  3. Sep 16, 2008 #2
    1 Farad is 1 Ampere second per Volt. 1 F = 1 As/V.
    1 Ah = 3600 As
    3600 As / 12V = 300 As/V = 300F
    But you need more then that because the voltage will drop as the capacitor discharges. Half the charge means half the voltage.
    With a lead acid battery that's different. A battery that is half empty still has nearly the same voltage as it had at the start.
    Maybe 600F and some electronics to automatically step up the voltage so it stays at 12V.
    So you'd need to buy 160 capacitors with 3V and 60F each.
  4. Sep 16, 2008 #3


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    Staff: Mentor

    You will want to calculate each in terms of energy stored:

    E = 1/2 C V^2 for a capacitor

    E = P * time for a battery (P = V * I)

    EDIT -- DrZ was too fast for me!
  5. Sep 16, 2008 #4
    O... yeah so running it off capacitors was even more impractical than i thought. Thanks for the quick responses! This puts everything into perspective better for me.
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