Few tech questions on 70s cart. resistor pack and throttle contactors

fastline

Hey guys. Looked like there was some good info here so figured I would join and throw around some questions. Friend of mine picked up a cart. I am in the engineering field and do a lot with electronics so I offered to help out, but I had to study the cart a bit to understand the design. I had him replace all the batteries, cables, and throttle contacts, as well as the bolts on the resistor pack and clean ALL contacts. New power solenoid, key switch, etc.

He ended up breaking the safety disconnect switch on the throttle, which appears to be a NC (normally closed) switch but that would open the circuit when off the pedal. So right now when you turn the key on and go to FWD or REV, it moves. No biggy, we will get that switch and fix that issue.

I realize by design, the cart burns off power at slow speed through the resistors. Not a big fan of all that wasted power but thats how they are I guess. I did notice the slow speed coil glowing when cruising, alarming everyone, but I am pretty certain that is normal?

The way it is wired up, at the slowest speed, power is taken to the lowest resistance coil to burn off the most power? Then as you roll up, the resistance goes up, allowing more of the power to go to the motor? Then at top speed, all resistors are bypassed and full power goes to the motor?

However, during testing, I noticed that as I roll up on the throttle, it seems to arc and surge to top speed when the highest setting is reached. It does feel like all the resistors are functioning but I really feel about mid throttle it should do a bit more. Is the arcing and power surge at full power pretty normal for these?

I sort of suspect he did not do a perfect job of aligning all the pads so they are flat and as the moving pad moves along, it may not be striking the high speed pad perfect? Is there a simple way to check this stuff without disconnecting all the leads? I really wanted to check all this stuff before he wired it up. I know inspection with a meter will now be difficult with the resistors connected. I just don;t like the arcing and surge at full power.


Also, has anyone modded one of these with a real PWM (pulse width modulation) motor controller? I realize most modern carts use a brushless motor but wondering if anyone has adapted one? I just don't like all the wasted power going to the resistors.

BGW

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Golf cart guy

You can convert it over to solid state, its an easy conversion.

That system had lots of issue. Filing of the stationary and moveable contacts was a constant battle with the way golfers drove the carts. Chances are good if you look at the moveable contact, only a sliver of it is really touching the contacts. File smooth ( you dont have to disconnect any wires) You can lift the board up and into a position to file the contacts.

fastline

Ha,yep, I noticed just this after posting and was trying to determine the easiest way to fix. I suspect the old contacts were probably worn to the correct angle and it appears the arm that the moving contact is attached to is worn causing the moving contact to present at an angle. You can see the contact pattern now.

So I assume the solid state system just goes through a series of basic switches and lets the solid state relays take the place of the actual contacts? So no half *** made contacts, either on or off.......