From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: Ultracapacitors and little racing cars
Date: Fri, 27 Dec 2002 06:57:42 GMT
NNTP-Posting-Date: Thu, 26 Dec 2002 22:57:42 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
> I got one of those really small remote control cars for Christmas.
> It's about the size of a matchbox car, and runs off a tiny
> ulracapacitor in the body. The circuit board is exceedingly small,
> with components I can barely make out. It runs about five minutes
> after a full charge, and takes about 45 seconds to charge. Of course
> I completely took it apart to investigate how it works, and now I have
> some questions.
> A) I wanted to find the resistance of the ultracapacitor, and so tried
> to discharge it before making the attempt. However, this proved
> harder than I thought. I had to leave the thing shorted for upwards
> of 20 minutes before the voltage between the poles dropped to zero.
> This is shorted, mind, with just a plain wire between the contacts.
> (First I tried discharging it through a resistor, but the only one I
> had around was about 216K and it was taking forever. Then I tried
> discharging it through the ampmeter on my DMM, but that also took
> forever. The current was on the order of tenths of a milliamp.
> Finally the shorting worked...but again this took forever. The device
> CHARGES in 45 seconds, why can't it completely discharge in 45?
> B) Why don't we use these ultracapacitors in more things instead of
> BTW, racing these tiny cars is awesome. Get one if you can :P. I
> picked mine up for about $12.
Capacitors that "bounce back" after being shorted for a while have a
large adsorption in the insulator itself.
The CRT (pix tube) in your TV set can do this, and they have been
known to hold a nasty charge for months on end.
A car battery can be considered a fixed voltage capacitor, with the
adsorption being chemical in nature.
Ultracapacitors, i think are like a hybrid between a "normal"
capacitor and a battery.
Ultracapacitors are expensive, and so will be found only where cost is
not the main consideration.
What are these cars called, brands, what do i look for, etc ?