I have a 2016 (early model) E6. I just installed 9 new 8 volt batteries. After charging them for 24 hours, I took it out for a test ride, it performed as it should reaching 25 MPH, after a few minutes it would not go above 15 MPH. It started to make a clicking/low sound grinding while driving, I thought something was stuck under it, I stopped to look, and did not see anything. If I let off the accelerator pedal the sound would nearly go away. There were no error codes, but the service wrench was illuminated on the instrument panel, then the panel went dead, and the cart would not move. It sat for about an hour while I got help to tow it home. After towing it home the instrument panel lit back up, the service wrench was gone, all seemed fine the next day, so I took it out for a spin and all repeated, except it did not die. Any help in what may be wrong is appreciated. Also, I live in central NJ, does anyone know of a mechanic in this area that works on GEM?
It kinda sounds like your brushes are popping/arcing inside the motor.
The noise will be more obvious in high load conditions (accelerating) and less when backed off.
A stuck brush will also account for the lack of speed. The noise is a kind of low popping, grumbly, grinding, evil sound.
Short answer: You probably should take your motor out for service. Especially since you do not really know the history.
Depending on your talent pool and how ambitious you are, sometimes you can unstick a brush(if the car hasn’t been used in a while) by removing the band clamp around the outboard end of the motor (you may need to remove the battery cables that get in the way) and see what is going on in there. If really black and dusty hit it with a good blast of compressed air. If alot of carbon dust comes out then it has been a while since anyone has been in there. You probably have holes in the end where it mounts at the gearbox. Blow in those too.
Usually a wrench light will also throw a code. Next time it happens make special note of what the speed shows. There are a couple of things that might make the display go dead but difficult to find when everything is working. Bring a go bag of some simple tools and a meter so you can do some diagnostics when it is dead-dead and awaiting the tow car to get you home.
Check all those battery connections. Rodney rule says “Tight and Bright”.
Take a read on each battery at full charge and then full pack Volts. If the car goes dead again you can check the batteries again and see if any of them happen to be lower than the others. If you check across a battery and it is good, then move one lead to the next post of the next battery it should show you no voltage drop. (This checks the connection across batts.)