How are the cables? Did the terminal corrode off, or melt off under stress? My dad's cart lost a couple terminals due to bad cables making a bad connection, caused a "clog" in the line, and boom. If your batteries are new, I'd spend the coin and do new cables. You can buy a kit, or get 4 gauge wire from the welding shop that's pretty easy to work with, and do it yourself. I rebuilt all the cables for Pop's cart in a day, and that included stripping the cart down to the frame to make it easier to work on.
If that's not in the budget right now, get a can of battery terminal cleaner from AutoZone, and a wire brush. Take the cables off one by one, spray them with the cleaner and brush them clean real real well. If the cable ends are pockmarked at all, take a little sandpaper and make them smooth. Any deviations in surface can cause shorts. Then rinse and dry. I've used THIS STUFF
for years and years, a little bit goes a long way. Get a good thin layer over EVERYTHING, cable ends, battery terminals, terminal nut, all of it, and put it back together. It'll keep corrosion at bay far longer than any of the other stuff I've tried.
Pop's cart had everything from old factory cables to short battery ground cables like you would get for your car. The holes in the short ground cable terminals were too large, and the resulting gap caused one of the shorts that melted a terminal. They warrantied the first one, we paid for the second one, and I got the stuff to remake the cables. Proper terminal lugs, soldered connections, crimped over solder, no ox on the terminal, which was then tubed with heat shrink tubing. Then copious amounts of the no-ox over everything electrical, and haven't had an issue since.
Brought the torque and power level way up as well.