solar panel regulator - terminating wires

Soldering may be a cheaper option instead of buying a radial crimper thats not much use for anything else.

The problem with soldering, I'm assuming you mean the wire ends is when used in screw terminals is that it can soften due to heating allowing the the wire to come loose and either come adrift or arc. I have seen many instances of this over the years some leading to electrical fires.

It is worth buying a good quality crimper with replaceable jaw sets.

Both mentioned in yours and my post have issues, the only real way is proper termination and making sure the cables are securer after the termination.