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AVSIG Discussion Sections >> Hardware/Software

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Ralph Jones
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Reged: 08/31/01
Posts: 21214
Loc: 4CO2
Marvelous invention
      #125923 - 09/08/06 05:55 AM

Just bought a handy little item from Black & Decker they call a "battery maintainer": a small, 1- or 2-amp smart charger that switches itself to a float charge and keeps a 12-volt battery topped up.

But what's really impressive is that, according to the instructions, it charges with "High-frequency pure DC current". The EEs must be doing great things these days...;-)

--------------------
Ralph Jones
LS-4a N49LS 6R


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Dan Barclay [ORG]
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Reged: 05/06/04
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Marvelous invention [Re: Ralph Jones]
      #125959 - 09/08/06 09:28 AM

>> The EEs must be doing great
>> things these days...;-)

Always have!

Dan <vbg>


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John Cooper [KAVL]
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Reged: 04/28/05
Posts: 13640
Re: Marvelous invention [Re: Ralph Jones]
      #125987 - 09/08/06 03:40 PM

Where have you been, man???

These gizmos have been out for over ten years now. The first one I know of was the Battery Tender by Deltec down in Florida. The chargers they made were marketed to the motorcycle crowd up North, who parked their bikes over the winter. Riding lawn mowers and ski-mobiles, too.

They have a five-year no-questions-asked guarantee, which is good since I have had two of them fail. They used to sell for $50 or $60.

Wal-Mart makes a similar made-in-China item for about $22 (I've not had one of them fail.) (The Deltecs are made-in-China these days, too.)

I use one of the Wal-Mart models on the airplane down in my basement, and another on the Honda backup generator for my home.

Be aware that if you buy the Wal-Mart version and it fails within the warranty period, they *will not* replace it at the store. You have to send it back to Arkansas and in two months or so you will receive a replacement.


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Ralph Jones
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Reged: 08/31/01
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Loc: 4CO2
Re: Marvelous invention [Re: John Cooper [KAVL]]
      #125988 - 09/08/06 03:57 PM

Ummm...did you get the point about high-frequency pure DC?

--------------------
Ralph Jones
LS-4a N49LS 6R


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John Cooper [KAVL]
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Reged: 04/28/05
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Re: Marvelous invention [Re: Ralph Jones]
      #125990 - 09/08/06 04:05 PM

Quote:

Ummm...did you get the point about high-frequency pure DC?



Actually, yes. Having a EE degree, I understand that what they really meant, which may have confused the lay public.

They were talking about a switching power supply, which uses a high-frequency oscillator which is then rectified to "pure" DC.

The chargers for your battery drill are like that, too.

I really hate those things. They interfere with the AM stations on the radio and make it hard for me to receive Rush Limbaugh <G>.

--------------------
"Where government moves in, community retreats, civil society disintegrates, and our ability to control our own destiny atrophies. . . . The result is a debased, debauched culture which finds moral depravity entertaining and virtue contemptible." - Judge Janis Rogers Brown


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Ralph Jones
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Reged: 08/31/01
Posts: 21214
Loc: 4CO2
Re: Marvelous invention [Re: John Cooper [KAVL]]
      #125994 - 09/08/06 04:29 PM

It's not the "lay public" that's confused: it's the guy who asked the engineer how it works and then wrote the ad copy. High-frequency pure DC would indeed be quite an invention...though of limited usefulness, since it would go right through blocking capacitors <g>. And that's the gag.

--------------------
Ralph Jones
LS-4a N49LS 6R


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Steve White [AZ]
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Reged: 06/04/04
Posts: 324
Loc: Tempe, AZ
Re: Marvelous invention [Re: Ralph Jones]
      #127010 - 09/17/06 09:25 PM

Legit question from a non-EE ... does DC have a frequency?

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Bruce Gorrell [EQY]
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Reged: 04/29/04
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Loc: Charlotte, NC
Re: Marvelous invention [Re: Steve White [AZ]]
      #127068 - 09/18/06 11:15 AM

Yes. It's 0.

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Ralph Jones
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Reged: 08/31/01
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Loc: 4CO2
Re: Marvelous invention [Re: Steve White [AZ]]
      #127112 - 09/18/06 04:32 PM

Pure DC is, by definition, a value of current or voltage that is constant with respect to time...which can be interpreted mathematically as a sinusoid with zero frequency. "High frequency pure DC" is an oxymoron.

--------------------
Ralph Jones
LS-4a N49LS 6R


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Dan Barclay [ORG]
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Marvelous invention [Re: Ralph Jones]
      #127127 - 09/18/06 06:49 PM

>> "High frequency pure DC" is an oxymoron.

Yup. Except when you switch it on from off. But you knew that<g>.

Dan


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