<VV> Cold Solder?

[Tony Underwood]

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..