20 seconds is too short a time for that amount of heat to have built up in the wires just from resistance or normal running.
However, its about right for a short circuit explosion.
So Im wondering did the extreme temps in your earlier runs melt the solder, and then on the final 20 sec run, the wires were already shorting out across the capacitor -- give it one blip of amps on the throttle and bang. Just a thought.
As for what is causing the heat in your wires in the first place... not sure.
Bad soldered joints, bad/broken wires (this increases resistance and therefore heat).
Using a capacitor that wasnt rated for the battery voltage/amps draw you were putting through it?
Not sure m8. Sorry.
