Golf Cart frame shocking me

auraslip

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Mar 5, 2010
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Ok. So the frame shocks me and displays voltage on the meter. I can't seem to find any direct connection to the 48v system. Normally I wouldn't care but the car has fried 3 after market controllers and navitas has stated that it is most likely because the car has a short or is frame grounded.

ALL of these Chinese carts seem to show voltage on the frame and i need to get this sorted. EZGO, CLUB CAR, and YAMAHA don't have these issues. Probably because they're designed by actually EEs and not some chinese dude named 'lance.' Also godbless Curtis. I've had zero problems with their controllers and their documentation is great.

:arrow: capacitative coupling (would frame show pack voltage?) (would the car have to be running?)

:arrow: motor brush dust builds up on top of batteries and provides voltage path to frame(i see this all the time on flooded batteries when they are overfilled and leak out. we use sealed though)

:arrow: motor, controller, dc/dc reducer shorted

:arrow: frame intentionally grounded somewhere in the car (would not be surprised if the OEM did this lmao)

I don't think the frame is permanently grounded because the shock is instantaneous like a capacitor. Leads me to believe maybe other brands of golf carts have some sort of high value resistor from frame to ground to bleed off this stray voltage.

Any thoughts?
 
Best bet is to trace the wiring (not a lot of it in a cart, thankfully, compared to a car!), and ensure no wiring connects to the frame anywhere, first. (pinched wire, rubbed-insulation, deliberate connection, etc).

WHen you touch the frame and get shocked, or measure to the frame, what is the other thing you're touching or measuring reference to?

And what is the actual voltage?

If you use a high-resistance between the frame and the reference point, does the voltage drop? If it does then it's a leakage somewhere, if it doesn't then it's probably a hard connection or short to the frame.
 
Best bet is to trace the wiring (not a lot of it in a cart, thankfully, compared to a car!), and ensure no wiring connects to the frame anywhere, first. (pinched wire, rubbed-insulation, deliberate connection, etc).

It's on ALL of our carts from this manufacturer, so I don't think it's a short.

WHen you touch the frame and get shocked, or measure to the frame, what is the other thing you're touching or measuring reference to?

Battery pack ground


And what is the actual voltage?

Can't remember. Will check tomorrow.

If you use a high-resistance between the frame and the reference point, does the voltage drop? If it does then it's a leakage somewhere, if it doesn't then it's probably a hard connection or short to the frame.

I need to try this tomorrow. If it's a leak, couldn't I just connect a resistor to the frame somewhere from ground?

Good to see you're still kicking around here AW. It's been a long time!
 
auraslip said:
It's on ALL of our carts from this manufacturer, so I don't think it's a short
Nope, that's a design thing. :/

Is it worse on older ones, or ones with more use, or the same on all of them?

If the former, it's something that can accumulate and cause this, like brush dust in a motor (unlikely but perhaps the controllers they use leave B+ on the motor, and just PWM the ground).


WHen you touch the frame and get shocked, or measure to the frame, what is the other thing you're touching or measuring reference to?

Battery pack ground

Then the most likely thing is a leakage from something carrying B+.



If you use a high-resistance between the frame and the reference point, does the voltage drop? If it does then it's a leakage somewhere, if it doesn't then it's probably a hard connection or short to the frame.

I need to try this tomorrow. If it's a leak, couldn't I just connect a resistor to the frame somewhere from ground?

Yes, but keep in mind it means there will be a further drain on the batteries thru that resistor, so it should be high enough to not cause much drain, but low enough that no significant voltage develops across it.



Good to see you're still kicking around here AW. It's been a long time!
[/quote]
Oh, yeah, I'm still here. I quit moderating, but I still post my own projects, and help when I can.

Have you seen the stuff in the SB Cruiser trike thread lately? ;)
 
Cleaned off batteries to test brush dust hypothesis. Frame still putting out voltage.

40v from B- to frame (pack voltage is 48v)

If I ground to frame, voltage drops to 0v. And then immediately returns to 40v when I remove short.

Short is pulling 8ma from frame to B-

That cruiser is awesome lol mad max dream machine!
 
auraslip said:
Cleaned off batteries to test brush dust hypothesis. Frame still putting out voltage.
What if you disconnect the motor from teh controller? (B- first, then B+ if that doesnt' fix it)

There may be brush dust inside the motor conducting from B- to the motor frame, and then from there to the vehicle frame.

Generally you'd see a worse problem with vehicles that are used more, and with new ones with no usage, you'd see no problem at all, if it's motor brush dust.

40v from B- to frame (pack voltage is 48v)

What voltage is it to B+?


If I ground to frame, voltage drops to 0v. And then immediately returns to 40v when I remove short.

Short is pulling 8ma from frame to B-
Then at least it's not a hard short, but that seems like a high leakage current.



That cruiser is awesome lol mad max dream machine!
How far did you get in the thread? :) It's gonna end up a "woody" at some point, soon I hope. Might actually look "nice".
 
Ooook

An led taillight was shorted from its ground to the metal frame of the car through a mounting bolt rubbing the led pcb.

The light is 12v light so why is it getting 40v? Well the voltage drop from leds explains the 40v from 48v. The 48v is coming through the SOC meter which is tied to the same ground as the 12v system. Disconnected from battery ground the 8ma current is feeding into the ground rather than keeping the SOC memory active.

So with every thing hooked up it seems the only problem with this car is that the ground is shorted to the frame.


Im not sure if this would cause enough issues to blow up controllers? Silver fox motors says this is the issue. But im not sure since there is nothing else electrically connected to the frame on the vehicle.
 
auraslip said:
An led taillight was shorted from its ground to the metal frame of the car through a mounting bolt rubbing the led pcb.

The light is 12v light so why is it getting 40v? Well the voltage drop from leds explains the 40v from 48v. The 48v is coming through the SOC meter which is tied to the same ground as the 12v system. Disconnected from battery ground the 8ma current is feeding into the ground rather than keeping the SOC memory active.

So with every thing hooked up it seems the only problem with this car is that the ground is shorted to the frame.
There must be more than one short, though, or there could be no current. To get a current there must be a connection from positive to negative. (I'd kind of assumed there was already another connection that was intentional, somewhere).

Is there a current flow out of the B+ on the battery, too? If not, then I am not sure where the current could be going to.

Im not sure if this would cause enough issues to blow up controllers? Silver fox motors says this is the issue. But im not sure since there is nothing else electrically connected to the frame on the vehicle.
Depending on how they designed their controllers, any connection could be enough. If their case is not isolated, and is internally electrically connected to anything in the controller, then when powered up it could do all sorts of damage depending on what those connections are, and current flow thru them.
 
Sorry the 8ma wa from the leds in the taillight lighting up when i connected the DMM and it completed the cicuit to the battery. lol no joke. I didn't notice it because this is a cart with a bed that was up and covering the light.
Here is a pic of this 4x4 cart
13398358_301947120139288_1264030411_n.jpg

Here is a pic of front hubs13423549_1729023434021468_819341866_n.jpg
 
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