Last week I started a thread about battery chargers. One of the posters described a static charger and how to build it. Does anyone have any experience with these? How well do they work? I'll be back later today to check for responses.

-- Steve (bibleout@tds.net), July 03, 1999

Answers

Steve,

The short answer is -- they dont. Think power (watts = volts x current). The explanation below is greatly simplified, but illustrates the problem.

It is possible to build up a very large static charge, using long wires or parallel surfaces. That much is right. The problem is that the static charge is a substantial voltage -- but with very little current, so doesnt contain much power. Example -- a 12,000 volt static charge at 1 microamp is equal to only 0.012 watts. That isnt much power.

By the way, a static charge is what you feel when you rub your shoes across a carpet and then touch a piece of metal. Youll notice that you get an initial jolt, but then the charge is gone, and you feel nothing. Youve equalized the charge and its all over.

On the flip side, batteries usually put out substantial current, at relatively low voltage, but they must be charged over a long period of time in order to receive the power they need. For instance, a 12 volt battery might want to get charged at 10 amps for several hours. That is equal to 120 watts, for every hour that charging is needed.

The two are incompatible.

Another way of looking at it is that the static voltage is built up on a high impedance source which is then asked to charge a low impedance load. The most efficient energy transfer occurs when the source and load impedances are equal.

-- de (delewis@inetone.net), July 03, 1999.

de,

Thankyou!

-- Steve (bibleout@tds.net), July 03, 1999.

NASA tried one on the shuttle a few years back. It was ten miles long and generated a whopping twenty-eight or so volts. Looks good in theory and on the drawing board, but real world applications currently leave a lot of design gaps left to fill-in.

WW

-- Wildweasel (vtmldm@epix.net), July 03, 1999.

Wildweasel; Wasn't the NASA project a dud because it was in a vaccum and no air was across the wire ??? Besides how do you inflate a ballon in a vaccum, unless you use magnetic molecular memory metal. first developed in Philadelphia in 1978???

-- Furie (furieart@dnet.net), July 03, 1999.

IIRC, the NASA experiment ended when the cable delivered such an overload as to cause a catastrophic failure of the connection to the shuttle. Definintely more than a few ma.

-- Ron Schwarz (rs@clubvb.com.delete.this), July 04, 1999.

The impedence mismatch is made up for by the ignition coil which is used as a matching transformer. And though it is true that the amount of power derived from this seems small this should not persuade experimenters that the effect is not worth some exploration.

This device is a practical rendition of the Lord Kelvin Thunder Cloud Machine and has been proposed in other forms for serious power generation (see past issues of Popular Science/Mechanics).

My understanding is that the kinetic energy of charged particles/droplets being forced past the wire/grid is converted to a build up in charge on the accumulator surface. In a typical set up there are few charged particles except in a rain or fog which is driven by wind. The alternatives I have seen use a sprayer to create a consistent body of charged droplets which are carried through the grid by the wind.

The other thing is that it is inexpensive and relatively uncomplicated device, does not require a sophisticated technology base to impliment and works best when solar is at its worst.

I will be setting up a rig soon and will report back with a rate of charge I see (hopefull enough to overcome the internal leakage of the battery anyway).

-- ..- (dit@dot.dash), July 04, 1999.