I tried posting this earlier, but I got an error message when I went to
post it. So, I am not sure the first message went anywhere. If this is
a double post, I apologize.

I am attempting to build a resistance soldering unit from a small car
battery charger. I am following these directions:

http://www.trainweb.org/girr/tips/tips1/solderer.pdf

I am using a 12v 6a charger that, I think, is too small. I can just get
two pieces of .005 brass sheet soldered together before the charger
circuit breaker shuts off the charger. The charger will run for about
6-7 seconds. This should heat it up within 3 seconds. I would like to
solder up to around .025 brass sheets together too. I found a 12/30/75
amp charger at Menards that is probably my next step. But I would like
to be able to vary the current coming out. Do I need a variac for this?
Does this go on the input (110v) or the output (12v) side of the
charger? What specs (volts/amps/watts) should I look for on this? I
also know that I could use a filament transformer of around 6.3v 6-20
amps on the secondary in place of the battery charger. Any suggestions
on which is better? I KNOW that using a light dimmer switch for the
adjustment setting is a bad idea.

I already know that American Beauty and PBL sells these. But for around
$500 for a 250 watt model, I think I will screw around with this some
more. I am bidding on a 300 watt model on ebay right now.

I also searched around the Internet for more instructions. But
everything I found was pretty vague. I am electronics illiterate, but I
can usually figure stuff out with some clear directions.

ANY help on this would be greatly appreciated.

THANKS!

Mike