by Andy77e - 7/5/07 12:08 AM
In Reply to: Amen! by FredMars
Capacitors are great. Super fast charge time, from hours to minutes. Completely awesome efficiency rate. Since there is no energy change, (physics: Energy can't be created or destroyed, it can only change forms. Energy is lost every time it changes forms) it thus has no loss of energy. Practically speaking, whatever you put into a capacitor, you get out of a capacitor. (unlike a battery where charging it loses at least 15% of the power)
This is all great, and it really really is. But there is one issue. One big issue. Have you ever seen a 1 farad cap short out? I did. Only once. That was enough. A Supercapacitor, or ultracapacitor (both names are used), is one that holds a kilofarad. Understand that 1 farad is more than enough to knock you on your butt or worse. A kilofarad... if you survive... start buying lottery tickets.
If you short a car battery is makes sparks. If you short it through you, it zaps a little. This is because the electrical energy is stored chemically. That chemical process takes time. Not all of that batteries potential power is available at all times.
Not so with a capacitor. 100% of that caps power is available, and will discharge in a fraction of a second. It will kill you. So if they intend to use ultracaps, that's ok, but they better have one **** of a good safety system to protect from shorts. If you get hit, and that cap shorts out on the frame, it could discharge in any number of ways, and if you, or someone else ends up in the path, it's comparable to lighting. Plus the cap itself could very quickly end up a fireball from the heat created from such a fast discharge.
I tried to find a suitable video clip. Luckly no one was stupid enough to try a 1 farad cap. Here's a 100 uf 333 volt cap.
Picture that 10,000 times stronger... that's a farad.
Now picture this 10,000,000 times stronger, that's a kiloFarad.
Now picture that amount of power being discharged somewhere very very close to you... bit scary eh? I agree.
I am for this technology, but cautiously...
I was surprised they used a three phase AC motor. I realize AC motors are more efficient... but inverters, which would be required to turn DC current from either a battery or supercap, into AC current, would lose efficiency. Plus an inverter to three phase AC would lose more. Looks like I need to go back and read up on AC fundamentals since they must know something I do not.
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