No Frame Ground! Electric Golf Carts and such systems

[Industrial Toys]

Well, Assumption really is the mother of all frick-ups it seems.

I have a 48 Volt Gator Utility Vehicle. Basically, the same system as an electric Golf Cart. I spent a lot of time installing a Motorola VHF radio recently. It was obviously 12 Volt, negaive ground. No problem. I just went on E-Bay and bought a 48 to 12 volt converter.

Then I realized something strange. I was getting no voltage reference to frame. A look in the scematics, indicated no such connection! The few things requiring a negative return had a lead running back to the battery.

There is almost no information on the E-Gators at all, and very little on grounding matters of electric carts.

Basically, they say, NEVER to ground the frame of such a vehicle to B-.

Some say it is safety. Remember this is 48 volt, not 12.

Any body know anything about this?

Right now, my radio is basically grounding the frame through the radio bracket and via a quarter wave antenna mounted on the roll bar. I could easily isolate the mounting bracket, but the antenna is a different matter.

What if I just fuse the negative lead, at say 20 amps?

 

[k0ua]

Hm.... I am not sure I like that ground path thru that coax and antenna.. How about putting one of those half wave no ground required VHF antennas like they put on corvettes (fiberglass body) instead of the 1/4 wave. If you get a failure in the ground return cable, I think starter current could go thru your radio. I am not sure what I would do.. I need to think on this some more.

 

[BigRol]

Rechargeable handheld VHF and mount?

 

[joefromga]

You don't need a convertor to get 12v. You just tap the first two batteries and you have 12v since they are in series. You can ground the frame at that point.

This is how golf carts are wired as well and how you add 12v radios and lights to golf carts and buggies.

36v have 6 6v batteries, and 48v have 8 6v batteries. Each set of terminals have their own voltage and each pair wired in series have double that (12v). Just ground from there to frame and use the hot from there (12v) to your radio.

 

[Industrial Toys]

Thanks!

I did not want to tap off the batteries as I figured that the radio might be on for extended periods and I did not know what effect it would have, having two batteries always lower than the rest.

I have a couple of Motorola HT 1000s (handhelds) that I use, but they are never around when you need them and I am not having good luck with the Chinese batteries that I bought for them.

I like the non ground plane antenna idea. I had to install an old Beehive style antenna mount, as the roll bar had 3/16 thick steel and a (standard) NMO mount would not work.

I would still like to know WHY such systems arn't and shouldn't be grounded to frame.

I did learn that the Auto industry was seriously going to convert from 12 V to 42 Volt systems back in the 90s. It got scrapped for a variety of reasons.

 

[joefromga]

When wet it has the potential to zap you.

The radio won't draw much current from 2 giant buggy batteries. What's the ahr rating of them? Without transmitting it probably draws less than half an ahr.

If you work during the daytime you can add a solar panel to it as well which would negate the draw.

 

[Xfaxman]

Did you connect the negative output of the converter to the frame?

That should work, since the 48v system is not grounded to the frame.

And a fuse in the positive output of the converter should be all that you need.

 

[Industrial Toys]

I really don't want to rework my antenna setup. It took me a long time to hide all the wiring for antenna and strobe light in the roll bar (thus also destroying the certification).

There are four wires coming out of the converter 48 volt in, 12 volt out and the two blacks are common. I was surprised and relieved that the metal heat sink case is floating.

So, for the time being, I will just fuse the negative, thus grounding the frame. I will however, use a two pole switch so this is only effective while the switch for the converter is on.

Someone at Deere that designed and works on these things knows why things are this way. In a by gone era, I could have reached him. Not any more. Very sad times!

If the motor has potentially high field voltage and current, maybe they don't want that thing grounded. I wonder if the Polaris 48 volt UTV has a grounded frame.

 

[Xfaxman]

-------- I wonder if the Polaris 48 volt UTV has a grounded frame.

No, it is not grounded and I don't know why.

But it is a neat UTV, so powerful it will climb a tree!

 

[Industrial Toys]

Letting weekend visitors touch your stuff.

The E-Gator may be terribly slow, but hey, it doesn't have to be fast, it's got a radio! Well, maybe some day.