Kind of past that now. The wrap and the bad joint was enough to give the same resistance as the other lead, and it charges the battery fine (they only charge at up to 10v, 3A).
It’s more for the skill building and some other things that I know I need to solder.
General priciples - I apologize if these are too simplistic.
Clean soldering tip! Tinned. Make sure the solder is appropriate (i.e. no plumbing solder for electronics). The tinning on the tip is the first heat pathway to the joint.
Setting up the fixturing of the parts is usually the most complicated part of the job, and can be an art in itself. As said ealier, you don't want them to move.
There must be physical contact between the parts. Since you often can't touch them all at the same time with the tip, heat needs to flow between them. In my experience, the flux is very helpful in facilitating heat flow.
Never use the tip to "dip" solder onto the work. This seldom works.
Do use the tip to try to evenly heat all the parts. The solder follows the heat. No heat, no solder flow. After fixturing, heat flow should be your primary area of focus. Note - this would also apply to soldering plumbing copper with a torch.
Once solder is where it needs to be, do not disturb the joint.
It's best practice to clean off the visible flux, and is usually required for professional electrical joints.
