I am building a rail gun for a physics project, but I am confused on whether to use capacitors like 2.7V 500F capacitors or a 400V 3300uF capacitor. Most tutorials seem to use many 400V ones in parallel but I can't afford more than one. Initially I was planning to use 4 of the 2.7V caps in series to attain 10.8V at 125F.
The potential energy stored in a capacitor is 0.5 * C * V^2. The 400V capacitor would store around 264J while 4 2.7V caps in series would store around 7290J! Considering the railgun would at best be 20% efficient, the 2.7V caps seem to be a much better idea, but I haven't seen anyone using them, why? So which one would you guys recommend.
The only compromise I see with using the 2.7V caps is using a much longer barrel for as much of electrical energy to be converted to kinetic energy as the caps store a lot more charge and discharge slower because of the lower voltage.
I plan to use copper rails with a steel ball, 10mm used in ball bearings as the the projectile. I thought of giving it some initial velocity by pushing it with a spring to prevent it from welding itself to the rails. If you have any suggestions for these stuff also, that would be appreciated. Thank you.
Edit: Thank you guys, I will keep these things in mind. I do know that such high currents I dangerous, thank for the heads up anyways. I am wondering though whether I will actually attain such dangerous velocities with a very basic DIY design as I thought I would lose most of the energy to friction and heat. Also, I am worried about my capacitors blowing up, since I would be basically short the capacitors and they have a peak current rating of 180A. Should I add a huge resistor or even an old bulb to increase the resistance of my whole circuit? Or as Samuel weir mentioned scaling it down to safer levels. What do you guys think about 4 9V 1F capacitors in parallel?
Initially I was considering using something like these : https://www.mouser.in/ProductDetail/AVX/SCCY68B407SSB?qs=sGA
Here is the link for the 9V 1F I am thinking of now : https://www.mouser.in/ProductDetail/AVX/SCMR22L105SRBB0?qs=sGAEpiMZZMuDCPMZUZ%252BYl6pWnZvuEsiEPl7ldT8lrOU%3D
Any other capacitors you guys can suggest with lower potential energy levels that would work, I will use smaller projectiles if necessary also.