The cables that connect golf cart batteries should be 6 gauge or larger. Sometimes a person will make their own cable by squeezing on a lug with a vice.
A potential problem occurs when the cable inside the lug becomes loose and causes resistance. If you ever see a golf cart battery terminal melt, most likely it was caused by a bad cable.
I found this video on golf cart battery cable. I do not know the author or his company but his explanation of golf cart cable trouble is good.