Super capacitor charging

Thread Starter


Joined Sep 28, 2012
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?


Joined Feb 5, 2010
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.


Joined Mar 14, 2008
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.


Joined Nov 21, 2011
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.

Thread Starter


Joined Sep 28, 2012
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.

The 2600F had a better F/$ ratio :D


Joined Jul 13, 2008
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.......


Joined Aug 16, 2010
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...