Electric Grounding Question

[yurtle]

I'm attempting to rewire a golf cart I bought used, with three separate 12 volt circuits. I was surprised to see that the cart appears to be positive grounded. Without unwiring the accessories installed by previous owners to see if this is something they did, is the chassis normally connected to 36 volt positive, or does the chassis normally float?

[roady89]

NEVER ground an electric cart to frame. There should be no voltage to frame. You either have a bare wire or you need to clean your batteries.

[yurtle]

There is currently at least one hard wire from 36 volt positive to the chassis. I can remove it, but wanted to know if it would change anything, before chasing down other previous "sins".

[yurtle]

I just removed the offending wire, and now the frame floats.

Why is it so terrible to ground the frame? The only real change would be that it would eliminate the need to fuse all four wires, as one would be ground. I'm the third owner that's had this thing positive grounded, with no apparent ill effect. I can see how wet batteries might have more of a tendency to discharge to a negative frame, as they got closer to the 36 volt positive, but is there any other reason other than "don't do it"?

[roady89]

Erroneous voltage spikes can and WILL destroy electronic controllers, radios etc. If its a resistor cart it MIGHT not be a problem. I still wouldn't do it.

[yurtle]

It's a resister cart, but I'll take your advise and keep the chassis floating. Heck, fuses are cheap.

thanks
Adam

[billy2moto]

Originally Posted by roady89

NEVER ground an electric cart to frame. There should be no voltage to frame. You either have a bare wire or you need to clean your batteries.

I have a similar problem. ..The frame shows around +37V to the negative battery terminal. Nothing is connected to the frame. Connecting the negative terminal to the frame through an ammeter shows about 0.6mA, indicating a leakage resistance of 67K-ohms. When the direction switch is in the middle, the voltage floats to near zero. So I'm concluding the motor must have some leakage inside or maybe around the terminals. Batteries are brand new and clean.

Thanks for the advice about not grounding the frame. I'm in the process of adding lights and wanted additional brake lights on the canopy frame. The kind I got used a grounded frame connection which is what prompted me to measure and look here before using them. I assume there is no problem with using the first two batteries as the 12 volt source as that's what EzGo does with their factory lights.

2001 ExGo Fleet Non-PDS

[scottyb]

Using two 6v batteries as a 12v source is cheap and easy ....... if you use those 12v accessories a lot it can be damaging to the pack during recharging.
The 2 accessory batteries will need more recharging than the 4 non accessory batteries.
The 4 will be overcharged while waiting for the other 2 to come up to cut off voltage.... actually, all the charger looks for is total pack cut off voltage. So the 4 get above normal and the 2 remain below normal charge voltage... then the pack goes back to work with 2 low batteries and those 2 get taxed even more.... this is a cycle which repeats itself & does shorten the useful life of the batteries..... a DC to DC reducer is best if you use your 12v accessories often.

[roady89]

At least leave enough wire so you can rotate which 2 are being drawn from.....but, like scotty said, its best to use a reducer.