I'm into model railroading, and I was modifying one of the cars to have extra LEDs.
There are 2 wires going through this car that connects to the tracks to receive power. I cut the red and black wires, connected everything correctly to the right polarity for the LED and the capacitor. So I apply full power to the car, 18 volts. The capacitor can take up to 50V (220uf).
All seemed fine, I cut the power to the train and the LED stayed lit for a few seconds as it's supposed to. So I decided to give it full power again and leave it so it can charge the capacitor. All of sudden I started hearing noises then BOOM!!!! The capacitor exploded around my face and burst into flames nearly killing me and destroying my house.
The film is completely out. I asked one of my friends and he said it's because the power going through the wires is AC and it can feed negative polarity to the positive wire.
Regardless, next time I must use a diode to keep the flow only "+" to the "+" leg. So my question is Why has this happened?
I'm now traumatized of ever using capacitors again.