5 mm Connectors

[BrianG]

That makes sense. Without that extra wire to take up some room, you'd have to use solder to fill it in and that's not as good as using solder to bond the metals. Think of it like glue in a way; most glues work much better with mated parts rather than filling gaps.

Basically, the idea of soldering is to heat the connector and wire so the solder will flow into the wire strands and onto the connector being soldered. You don't want to simply drop solder onto the wire/connector - you'll get a poor solder joint.

When soldering large guage wire to relatively large metal object (large connectors, etc), you have to use a fairly high power iron (100W+), or a medium powered one (>=40W) with a thick tip (more heat capacity) so it will retain the heat longer. Whatever you are soldering acts like a heatsink so if you are soldering large guage wire to a metal object, you'd have to have enough heat capacity and/or power to get the items hot enough to melt the solder before they pull too much heat from the iron and cool it to below the solder melting point.

If you try to use a smaller iron and just keep it on longer to compensate, you have to keep it on too long, and the wire and connector sinks the heat and the whole wire will get hot, not just the area to solder. You end up deforming the wire insulation and/or damaging whatever you are soldering to. Or, the smaller iron can't get the items hot enough and you get a cold solder joint.

You think that's hard, try soldering ring terminals on 2 GA wire sometime!