<VV> Cold Solder?

Tue Jul 5 23:20:06 EDT 2005

Alkaline AAs have an interior resistance of about 30 milliohms and an open
circuit voltage of about 1.2V.  So at 10 amps, they put out about .9V, or
about 9 watts each.  Two of them therefore give about 18 watts, which is
enough to solder small circuits.  At lower currents, they're good for about
2.5 amp-hrs, which would imply that they would go about 15 minutes, but
they're not capable of that at 10 amps.  So, say they might make 8-10
minutes.  That's still a lot of time if you don't have to keep the iron hot
between actual soldering activities.

I haven't tried one of these irons, but there's nothing theoretically wrong
with the concept.  Myself, I tend to want to solder 8 or 10 gauge copper
wire, so I need more heat.  I miss my old 250 watt gun.  ;-)

Roger

----- Original Message ----- 
From: "Bob & Kathy Gilbert" <bgilbert at redshift.bc.ca>
To: "'Tony Underwood'" <tonyu at roava.net>; <virtualvairs at corvair.org>
Sent: Tuesday, July 05, 2005 6:27 PM
Subject: RE: <VV> Cold Solder?

> As a flyer of fairly high powered electric model aircraft and helicopters
I
> can certainly attest to the energy density of modern batteries(Nicd, NIMH
> and Li-poly) but the ads I've seen for the typical $20 battery powered
> solder gun make a big deal about soldering with just a couple of AA cells.
> It might happen once or twice on small, carefully cleaned and prepared
> joints but not much beyond that.
>
> As always "yo's get what yo's pay fer".
>
> Bob
>
>
> -----Original Message-----
> From: virtualvairs-bounces at corvair.org
> [mailto:virtualvairs-bounces at corvair.org] On Behalf Of Tony Underwood
> Sent: July 5, 2005 2:34 PM
> To: virtualvairs at corvair.org
> Subject: Re: <VV> Cold Solder?
>
> At 08:36 hours 07/04/2005, John Kepler wrote:
>
>
>
> > > I just saw a mini-infomercial on TV for a thing called a Cold Solder
> gun.
> >I seems unlikely that it works as advertised. If anyone has tried one
> >of these, or know how it works, please let us know. Sells for $20, and
> >sure would be nice when working upside down under a Corvair dash :-)
> >
> >Let's put things in perspective.  Those little dinky "pencil" soldering
> >irons they sell at Radio Shack that just barely work draw 10 watts and
> >are about the minimum power required to adequately solder a SMALL
> >electrical connection with a low-melting point solder.  That "Ronco
> >Special As Seen On TV!  Cold Solder Gun" uses 4 AA batteries as a power
> >source.  Now, the science question for the day is:  How long do you
> >think 4 penlight batteries are going to keep a 10 watt light-bulb
> >burning (BTW, @ 6 volts, 10 watts requires 1.667 amps!)?  How many
> >watt/hours do 4 AA batteries produce?  When you finsish the math, you
> >should have a pretty good handle on how well it's actually going to work!
>
>
>
>
>
> Not arguing with you about the "cold solder" iron.   However, don't sell
> today's batteries short, especially the rechargeable types.   I have AA
> NiMh rechargables that are good for 2700 ma/hr.   And that's not an
> exaggeration.   These little suckers pack a serious wallop and will put
out
> high currents, sometimes amazingly high currents although admittedly for a
> short period of time.
>
> I've not "destructively tested" the NiMh AA cells I keep on hand for
stuff,
> but if you load them down bigtime, they'll put out as much as ten amps
upon
> loading them down to 1.1 volt and get the load resistor damned hot real
> quick.    Now, they won't do it for very long...   but 4 of 'em should run
> an efficient soldering iron long enough to solder a dozen or more medium
> duty connections.
>
>
>
> The hobby shop up the street does a LOT of battery testing for radio
> control race cars.   They load-test individual cells and use select
> examples to build battery packs which they sell for premium prices.   They
> showed me a test chart on a 12 volt pack made of C cells that was tested
out
> on a cycling load/charger setup which first optimizes the cells one at a
> time, then charges them fully and then will load the fully charged cell
> to 1 volt and note current output and for how long.   The pack he showed
me
> had c-cells that were charted to produce at least 30 amps for a total of
90
> seconds before individual cell voltage dropped below 1 volt.
>
>
> That's some serious output from a c-cell, nicad or NiMh or otherwise.
At
> work, I regularly deal with d-cell nicads that are rated at 5 amp/hr.
The
> same cells in NiMh are seen often in 4400 ma/hr ratings and offer
advantages
> of not having charger "memory" to reduce their life
> span.    These are serious pieces which will superheat and explode if you
> short one out... or used to; better quality cells these days have fusible
> links inside to open up if they're shorted dead out with a full charge,
thus
> removing the possibility of the battery actually spewing its insides all
> over the battery box of whatever it was in... as well as preventing the
> device from catching fire and going up in flames etc.
>
> Not all high capacity rechargeable cells have these fuse links...  so
don't
> short them out.
>
> By the way... a standard carbon-zinc d-cell, the cheapo ones on the hook
at
> the convenience store, when loaded down hard enough can deliver better
than
> 6-7 amps for a short time.
>
>
> tony..
>
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