A question about capacitors.

[jimbo2032]

Greetings,

After reviewing several rail gun designs that I have seen over the internet I have noticed that people predominately use 'pulse capacitor' banks as their power sources that have high voltages and relatively 'high' capacitances on the order of a few thousand uF. I have some experience with the 'newer' Electrolytic Dual-Layer Capacitors (EDLCs) and have been favorably impressed with their charge storage capabilities of 1-3000F (3.6-11000 J). Their only drawback is the very low rated voltage at around 2.5-2.7 volts. Does this disqualify them from use in this application? If so what makes them different other than rated voltage from a 'pulse capacitor'.

Jimbo

[powerlabs]

Very large internal resistance is what makes them unsuitable. When it comes to capacitors, energy storage is almost always inversely proportional to internal resistance. The term "Pulse capacitor" refers to a capacitor that has very low internal resistance/impedance AND is internally strong enough to withstand very high current pulses. A large bank of EDLCs put in series in order to achieve a high voltage storage would have so much ESR (Equivalent Series Resistance) that it would act more like a battery, releasing its energy as a long low current pulse and dissipating a lot of the energy internally...