'99 ezgo 36 volt wires overheating!!

dad'lfixit

Here's my problem: a '99 ezgo,36 volt that the speed control box was replaced in.A year has gone by and now two of the black wires coming from the bottom/back of the fwd/rev swtch assy(one leading to the motor,one leading to the speed control box) are getting so hot they are melting.Is the motor shorting out pulling too much volts.I get about 20 minutes driving and then the batteries are dead.

BGW

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Legendary Golf Carts

What kind of controller do you have? (amperage) I believe your problem is you upgraded the controller without upgrading the cables and F/R to handle the high amperage.

dougmcp

If your batteries are dead the motor will draw more amperage and heat the wires.
Sounds like you need new batteries if they're dead in 20 minutes and you probably need to examine and replace your cables.
Check with a voltmeter, each battery should be 6.3v or better after charge and rest, if they are lower than 5.9v after 20 minutes they're done.

yurtle

Urban myth. Motor has a constant impedance, so Ohm's law dictates that as voltage drops, so does current.

scottyb

Can you explain this more? Currently many agree that as available voltage drops the amperage drawn for a given task increases.

yurtle

OK. I may have over-simplified.

To maintain a given horsepower output requires more amps (as voltage drops).

If you are applying more petal to counteract voltage drop, then I'm wrong.

However, if you have the petal to the metal, then as voltage drops, so does current (and horsepower).

scottyb

I see.

My answer to the original question is this.

I have seen stock ezgo carts with cargo box on hilly terrain in ranch use melt the F&R as you describe. The lug connections get so hot as to melt the plastic housing hold them. The result is they lean and mis-align themselves with the rotary switch cam contacts. At that point a new F&R is in order and so is some system upgrade, like fresh bigger cables & HD switch cam to help avoid a repeat of the problem.

JohnnieB

Urban Myth #2

The DC resistance doesn't change because it is determined by the length, diameter and metallurgy of the windings, but the Impedance is directly proportional to the RPM. A stalled motor has minimum impedance and maximum current while a motor spinning at quiescence have maximal impedance and minimal current as dictated by Ohm's law.

Investigate Back EMF vs. RPM vs. Amps vs. Voltage. It is all tied together and confusing as hell, but if you take it back to basic electronics, it becomes clear.

I see others have replied already, but I'll post this anyway.

yurtle

You're absolutely correct. I'm wrong here, if the load (output horsepower) is constant.

Once a person and controller is involved, thing get different. If you apply more petal to account for dropping voltage, then I'm wrong. I still believe that for a set amount of petal, as voltage drops, so does amperage, and horsepower (but I may be wrong).

yurtle

So are you agreeing or disagreeing with me?

I deal with 3 phase constant speed motors at work, and when voltage droops, so does current (and output Hp).

I admit, I maybe wrong with a chopper controller involved (and heavy footed driver).