There is a possible problem using banana plugs for high current. Most people are going to use the banana leads they have accumulated over time and most of those leads have fairly low current ratings. If they are the cheaper Chinese leads, the ratings may also be grossly exaggerated. I believe Dave did a review of leads and found some of the cheap leads he ordered were actually open as received. Also the compressible springs on some didn’t even break through the oxide layer on the cheap plating so the resistance between the spring and the pin was quite high. You can easily spin these springs when they aren’t plugged in and visualize how much contact area there is between the spring and the pin IF it is making good contact.
I have assembled some leads using high count stranded test wire that will handle higher currents and on the banana plugs have soldered one end of the spring to the center pin to be sure there is good contact. If you look at the photo below of the soldered plug, you will see that I made sure there is a gap left at one end of the spring so when it is compressed, and lengthens, it doesn’t bind. I have used banana leads like this for testing with higher current supplies and electronic loads, but only for short tests. For continuous testing I use #12 or #10 stranded wire and compression lugs and the posts and I wouldn’t trust any banana plug no matter what the claimed rating is. At one place I worked we used what amounted to huge banana plugs rated for 200A so I know there are ways of doing it safely.
Below is a photo of a jack from a B&K Precision 32V/20A bench supply. I got it really cheap because someone had used the hole in the end of the binding post for a banana jack and the high resistance and generated heat melted the post’s plastic mounting hardware. Fortunately the damage was localized to the post so I could repair the unit by buying some of the M6 binding post others have shown. I found these to be of good quality and they do have the 4 mm hole in the end for a banana plug. You can see the dimensions of the binding posts in the photo below. For $7.95 they seem to be a good deal. That being said, I’ll still stick to heavy wire with lugs for any long term testing.