Afrotechmods
3 HN recommenders · recommended in 3 months, 2013–2020
6:11 · 2.2M views · Dec 13, 2010
Afrotechmods plays with 2600F ultracapacitors that can dump hundreds of amps, shorting them to vaporize bits of metal. Along the way he explains the three most important capacitor equations. The uploader warns that the capacitors are not designed to be shorted.
HN commenters use it as a vivid, math-backed demonstration of what ultracapacitors can do and why shorting them is dangerous.
3 comments from Hacker News
Here is my favorite movie about ultracapacitors: this video Very good explanation on the general math and physics of capacitors, current, heat and energy storage, plus awesome demonstrations at the same time :)
Shorting batteries is also never a great idea, but supercaps are more dangerous because of their low internal resistance. This video is a good demonstration: this video I was working on a controls project where we had large banks of supercaps that would charge up to ~900v. Have to treat those with some respect. However as long as they are kept cool the caps had no trouble being charged and discharged with a couple minute cycle with each bank providing 2kWh of energy. In the particular application I was working on we actually had 17 2kWh banks providing ~34kWh of energy every couple minutes. Would not fit in a cellphone though :)
Capacitors are great for high load requirements but not great as an energy storage device. i.e. if you wanted to draw several hundred amps for a second or two with relatively low heat waste, an ultra-capacitor arrangement would be the way to go, but for energy storage, a battery wins hands down. There's huge research going into expanding the capacity of capacitors. Check out this video about capacitors: this video