Here’s a weird arc-welding meets soldering hack. You can use a 12 volt car battery (or charger) and a length of graphite pencil to solder connections. The graphite is connected to one jumper cable and a length of solder to the other. Touching them both to the connection closes the circuit, heats up the connection point, and melts the solder. I’m guessing this works best if you connect the graphite and solder to either side of the component connection, which would conduct over the component lead, heating it and causing the solder to wick into the joint.

I’m not sure how well this works or how hard it is on your battery, but it looks like it might be a good way to solder small and difficult connections without overheating components.

Anyone care to chime in on the effectiveness of this or any specific precautions that should be taken?

Graphite Pencil Soldering – Link