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need help with capacitance and slow discharge! Answered

i need to make a slow dishcharge capacitor bank capable of discharging 12 volts at about half an amp over about 5 seconds. What sort of capacitor and resistors should i use? It will be powering a short length of nichrome.  thanks :)


Without clever electronics, the capacitor will discharge exponentially, the voltage will decay from a maximum value, and current will follow it.

If you equate the ENERGY dissipated to energy stored in the cap, then IVt = 12 x 0.5 x 5 = 30 Joules....

For the capactitor E=CV^2/2 so 30 x 2/12^2 = 0.4 Farad.

If you aren't careful, the initial discharge will blow your wire.


With the requires you specify, you'd be better off using SLA batteries or something similar rather than wasting time trying to do it with capacitors.