Help with 2006 Ezgo PDS, but it's not

[AllElectric]

Originally Posted by JohnnieB

The rocker switch that EZGO used for a PDS F/R selector is a SPST/Center-Off switch, which is also the type switch used for aftermarket reversing contactor setups, so someone could have just replaced the keyswitch panel of a series cart with the keyswitch panel from a PDS cart.

The speed controller does not effect the cart's top speed. All it does is limit the number of amps the motor is allowed to draw and when wide open the motor is effectively connected directly to the battery pack. In other words, the only time the speed controller controls the cart's speed is when the throttle is less than 100%. Also, it doesn't push amps to the motor, it passes amps to the motor. Basically, it is functionally akin to a water valve or faucet.

The cart's speed is determined by the battery pack voltage, the height of the rear tires, the gear ratio in the transaxle (aka differential), the ratio of the magnetic field strengths produced by the motor's armature and stator windings and the cart's mechanical drag.

My guess is your cart has a 48V battery pack, 23" (or so) tall tires and a high speed motor, such as an AMD 7126.

What is your cart's pack voltage?
What is the Make/Model of motor?
What is the tire Height?

Thank you for your assistance. I understand the controller 'controls' amp draw from the battery pack.

So I understand what you said (bolded above): all else being equal, a cart with a 700amp controller will go the same speed as the same cart with a 275A controller operating at 100% throttle? Acceleration should differ?

To answer your questions:

- Cart is 36V (T-105s), pack voltage is a little over 38 when fully charged.
- I'll have to check on the motor specs, as I'm unsure. AMD might be a good call, as it is black.
- It runs on 10" wheels, I'll need to check the tire height, but it's not 23" closer to 20".

This means that the speed has to be a function of the motor and modified gearing in the cart? It shows relatively impressive torque, so the gears are getting help if that's what it is.

This controller is fairly large, guessing it's 10" long +/-; as the pics show, the usual ezgo controller cover has been removed to fit it. Looks to be a Curtis, 4 lug no plug brake, I just don't know the model or amps.

[Andy4639]

The model # and amps should be on the bottom side of it if they are there. Most controllers are this way.

Yes a 700amp controller is only going to help you get to the top speed faster...as in how many amps it can pass to get the cart rolling. The top speed will be the same on both carts being = other than controller amps 275 or 700.

As far as the cart getting hot are all the connections clean and tight? Depending on the motor and if it's performing good it could be the problem.

[AllElectric]

I'll pull it out and see what it is.

Poor cabling was my first reaction (given the heat), which is why I originally swapped all the old 4AWG out for 2AWG. It was after this swap that the cart topped at 20mph, cool cables but performance stunk. Really strange.

Thought maybe I had a bad crimp or something, so installed new 4AWG across the reverse contact and speed went back to 30, but the cables are again very hot. This is when it started exhibiting intermittent thermal shutdown.

I was wondering if I did something to damage the controller or reverse solenoid arrangement, or if it's manifesting the effects of long-term heat damage and I'm the victim of bad timing???

[JohnnieB]

The heat issues boil down to excessive resistance in the cables and connections and is made worse by running at 36V since it take more amps at a lower voltage to do the same amount of work that is done at a higher voltage. Amps through resistance produce heat. When the amps are increased, the heat produced is squared. (I² * R = W)

The speed you are getting is likely due to the motor since 20" tires only up the speed by 11%. But they also reduce the torque where rubber meets road by 10%, which in turn increases amps through the motor by a similar amount to the tires.

There may be high speed gears in the differential, but no easy way to verify other than pulling the motor and counting the number of time the input shaft has to be turned to make tires turn once, or something similar.