36v txt pulling too many amps

rockfordpi

Have a 36v txt series cart. Solenoid was welded closed and terminal on F/R switch burned. Replaced both and now wires from F/R switch to motor getting way too hot.

Logged amps. Up a slight slope with one 235 lb passenger cart pulls 100-150 amps at WOT, has been as high as 185 on steeper hill.

A1,A2,S1,S2 not shorted to case and no short between field and armature.

I am wondering if I have a short within the field or armature winding. I have seen this on AC motors, not sure how common/likely it would be on a golf cart motor. Can someone tell me what the Ohms for field and armature should be?

Very low Ohms on both field and Armature, but I do not have a good benchmark as to what a good number for those should be.

BGW

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scottyb

What motor and tires are we talking about. 100 amps could be well within reason for some setups.

ThreeCW

I may be comparing apples to oranges but under load I can be pulling 200 to 300 amps with my heavy cart and I never see heat build up in the cables or connections. But I will see heat in the controller and motor. Note that I am running 2 gauge cabling.

Heat in cables is typically caused by excessive resistance / poor connections / undersized cables. You might want to take a closer look at your cabling and connections.

I recall reading in a BGW post a few months back about load testing your cables to determine if there is an excessive voltage drop (and hence heat buildup) on a particular cable. It might be worth considering for your problem.

rockfordpi

This was with stock tires

rockfordpi

This is just a basic cart with stock tires and controller, I have worked with these before and just have never seen cables get this hot from just one trip down the driveway. I am sure I could put bigger cables on and reduce the heat in the cables, but I fear it would be just a matter of time before the F/R switch or Solenoid failed again if the motor is indeed pulling too many amps.

150 amps up slight slope with stock tires and only one person makes me think something more than bad cables is happening, especially given that it had previously burned up a solenoid and F/R switch. Then again, I don't really have a benchmark for amps, maybe 150 is normal?

ThreeCW

You did mention Wide Open Throttle ... perhaps that is normal.

Apples to oranges again, my heavy cart will pull 100 amps when I baby it up a moderate hill.

I have also read on this forum that a 36 volt cart will require more amps than a 48 volt cart ... makes sense from a power prospective.

You also mention that specific cables are getting hot ... this being a series cart, if it were an over amperage situation, I would suspect that all cables would be getting hot ... thus perhaps a specific cable or connection problem is causing the heat.

scottyb

I agree, 150 amps is high for a stock cart. 100-150 would be okay for aftermarket (bigger) motor.
I would replace or remove the motor and have it properly refreshed, armature turned, new brushes, new bearing.

JohnnieB

Motor cables disconnected
A1->A2 should be approximately 0.2Ω to 2.0Ω.
S1->S2 should be approximately 0.8Ω to 3.0Ω.

Ohmic values for Hi-speed, Hi-torque and aftermarket motors will be different, but in the same neighborhood.

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The slower a motor spins, the more amps it can draw.
The more amps it draws, the more voltage is lost in the cables.
The more voltage lost, the slower the cart goes.

If the temperature rise on any of the cables is greater the 10°F above the air temperature, it need to be fixed or replaced.


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I agree that motor ought to be refreshed.

rockfordpi

ohms are in the ranges given. Cables are getting well above 10 degrees above ambient.

One possible obvious thing I may have overlooked is the possibility that the batteries are collapsing under load. I don't think that is case and my guess is the controller would shut down before battery voltage drop alone caused amps to rise to 150.

At this point I guess the debate is between refresh vs replace. Have not had good luck turning/undercutting commutators.