Super capacitor charging

Discussion in 'General Electronics Chat' started by doller, Nov 8, 2012.

  1. doller

    Thread Starter New Member

    Sep 28, 2012
    14
    3
    Hi all,

    I am getting some 2600F, 2.5V caps and can't find much useful info how can they be charged in a reasonable amount of time, say couple of minutes.

    I can work the formulas but need help with technical info that is just too hard to locate. For example a welding power supply looks like a great cheap option but can it operate "short circuited"? Welding itself looks like doing just that but I just don't know. Can I use a pc power supply? A battery charger?
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,779
    932
    With a .1 ohm resistor to limit current to approx. 30 amps at startup(2.5 volt supply)

    The cap will take around 15-20 minutes to reach 2.5 volts

    Substitute a .01 ohm resistor and the time drops to 2 or 3 minutes, but the initial current draw peaks around 300 amps.

    Fast can be accomplished but will take HUGE currents to get the charge time under a minute.
     
  3. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,229
    A DC output welder might work but you need to check its duty-cycle to see if can charge the capacitor without exceeding its rating.

    How are you going to regulate the charging voltage to the cap? You could use a 2.5V voltage regulator but it could dissipate a lot of power, depending upon the source voltage, if you want a fast charge.
     
  4. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    :eek: Twenty-six Hundred Farad !!! ??? :eek: I gotta not be understanding the OP
     
  5. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,229
    He did say it was a super capacitor. ;)
     
  6. JMW

    Member

    Nov 21, 2011
    88
    8
    There are 3000 Farad caps available for 25 bucks or so on the favorite on line auction site. I have a 2.2 volt cordless drill. I'm thinking these might be a viable alternative to $30 buck battery packs that last a year.
     
  7. doller

    Thread Starter New Member

    Sep 28, 2012
    14
    3
    I could wire the caps in series, say 10. Then the setup should be able to accept 25V input. The welders I am eyeing can deliver 120-150 amps but I also read (on this site too) how caps behave like a dead short at first. Which makes me wonder what device could I use that won't care about working in such mode.

    @JMW
    The 2600F had a better F/$ ratio :D
     
  8. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    good grief.......I would hate to mishandle a charge like that !! :D
     
  9. MrChips

    Moderator

    Oct 2, 2009
    12,429
    3,360
    Where can you buy that? I want one... or many!
     
  10. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The 3000F caps for $25.00 each on E-Bay are USED ones.
     
  11. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    Don't know where to look yet for the conversion formula -- tho' I looked up the condensors used for starting diesel rail locomotives........[ railroad brat ] and they are listed in the neighborhood of 40 KiloJoules.......
     
  12. doller

    Thread Starter New Member

    Sep 28, 2012
    14
    3
    Here you go:
    [​IMG]
     
    PackratKing likes this.
  13. Papabravo

    Expert

    Feb 24, 2006
    10,137
    1,786
    You'll shoot yer eye out kid!
    -- Jean Shepherd
     
  14. JMac3108

    Active Member

    Aug 16, 2010
    349
    66
    Supercaps have a very shortened life if you exceed the 2.5V rating across them. If you put them in series you might need to take this into account...
     
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