Controller troubleshooting-voltage irregularities

Bubblerings

This is a 2000 txt ezgo, 36 volt, no tow/run switch, key on dash. F/n/R lever below seat.

Symptoms; After installing new batteries, solar panels and a new 4 horse motor (tech said my controller could handle the upgrade) it ran great for three months or so then a couple times acted up. It ran full throttle a few times even when foot was off the "gas". Then is just quit. Solenoid clicks but won't go.
(panels keep me charged well, have been for a couple years on my old trusty rusty. Battery pack is a volt or two low now cause it's under part shade in my shop)

Abilities; I can take anything apart.... learning by doing.

Work so far; New batteries, solar charging, new motor, new solenoid. Cart condition is real clean, no rust, not dirt yet, no moisture. ITS is new looking. I've ran the troubleshooting map in circles, literally. Bypassed Reed switch.
So far no continuity irregularities, good pins and plugs, lots of good voltage confirmations in solenoid etc.

Question; Is it the controller? Trouble shooting results on the controller are odd, I think.

Key off, F/n/R in neutral
M- to B- = 0 volts
M- to B+ = 37 volts
B- to B+ = 37 volts

Key on, F/n/R in Forward
M- to B- = 37 volts
M- to B+ =0 volts
B- to B+ = 37 volts

Key on, F/n/R in Forward, pedal down
M- to B- = 38 volts
M- to B+ =0 volts
B- to B+ = 38 volts

So, pedal down and voltage goes up to full pack. What's up with that? Controller or ITS?

BGW

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JohnnieB

Looks like you have a 2000 TXT with a series drive.

Either the controller or the throttle is bad.

Measuring for B- to M- is one of the best troubleshooting measurements since you are measuring across the MOSFETs in the controller and if you get battery pack voltage there when the pedal is pushed just far enough to make solenoid click, all of the high current cables, connections and contacts as well as the armature and stator coils in the motor are intact.

The reason the voltage isn't at zero when the solenoid contacts are open is due to the pre-charge resistor connected between the solenoid's large terminals, placing a parallel path for current flow when the solenoid contacts are open. The purpose of this resistor is to keep the filter capacitors inside the controller charged so the solenoid contacts don't arc as much when they close.

Sine the voltage between B- and M- does not decrease to nearly zero when pedal is on floor, either the throttle is not telling controller to pass amps, of the throttle is doing its job and the controller is not doing what it is told to do.

Attached is how top check the throttle. If it is good, the controller is bad.

Attached Images

	ITS Voltage - 1.jpg (47.7 KB, 0 views)
	ITS Voltage - 2.jpg (48.2 KB, 0 views)
	ITS Voltage - 3.jpg (44.2 KB, 0 views)

Bubblerings

First let me say it is an honor to get a response from the Doctor JohnnyB himself on my second post, I have read a bunch of your controller information already and learned a lot. Except what MOSFET stands for.

Ok, I get 14.2 volts on step 23, .55 volts on step 25 and 1.5 volts on step 26.

If going outside the range in step 23 is acceptable then change the controller? (that was one of my problems in the trouble shooting guide, no option for a reading over the range.)
Thanks, Tom

Bubblerings

If it's time to replace the controller I see the Curtis 36 V 275 Amp Controller but I also see an "upgraded" 350 amp controller by Best Turf West. What do you recommend? (only asking because I put in the 4 horse motor) Also are there other parts in the circuit I could replace that commonly burn out?

Thanks in advance for your reply.

yurtle

Did you use the troubleshooting guide in the Manual from the Stickies? There is an "If Then Else" for every step.

Chapter E, page E-8.

Technician's service and repair manual electric carts
http://products.jacobsen.com/img/manuals/28646.pdf

yurtle

I always start with site sponsors. They keep the light on here, and offer great customer service.

JohnnieB

The PhD I've got stands for Piled Higher and Deeper.
MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor. They either pass or block the amps going to the motor at about 18,000Hz. How long they stay on during each cycle determines the percent of available amps are passed to the motor. (0% to 100% duty cycle)

You are getting in range voltages for pedal up and pedal down, so the controller ought to be passing amps, which will drop the voltage between B- and M-. So the controller is being told top pass amps, but isn't doing it, meaning the controller is bad.

The Alltrax SR48400 (or larger) is what I recommend for a replacement. https://www.cartsunlimited.net/alltrax-sr-series--.html
It is user programmable, so you can tweak it to match your desires rather than being programmed by some committee consisting of lawyers and accountants.

If there is the possibility to upping the battery pack to 48V or going to Lithium, get a MJZ400 solenoid, it works at 36V now and 48V later.

With the higher power motor, you be needing a true HD F/R switch assembly (not all of them are true HD) or reversing contactor.

Also, all 13 high current cables ought to be 4Ga or thicker.

Bubblerings

Thanks Yurtle and JohnnyB,
Yes, used one of those stickies links. Very helpful. Having fun with this. Yes on the local companies too, motor arrived fast and tech was helpful.
JonnyB, think I gonna keep it simple. I’ll check the wire gauges but just going to be driving it around the flat yard for gardening help so no need for fancy controller. Guess I’ll just go stock unless you guys think the higher amp one is better.

yurtle

Bigger is always better, but if you're happy with stock, there is a For Sale place here, and lots of folks who upgrade their controllers sell their old ones there.

JohnnieB

Ironically, driving around the yard is one of the most demanding things you can do with a cart.

At low RPM the motor is capable of drawing the max amps the controller will pass, so motor heat and controller heat become issues. Having a 4hp motor also increases heat load on controller.

The stock series controller is a 275A unit and its heat dissipation abilities are marginally adequate for feeding a stock series motor turning stock height (18") tires. The "upgraded" series controllers rated at 350A are basically stock controllers with higher power rated MOSFETs in the same box that has marginal heat dissipation for 275A.

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If you have stock height or shorter tires, you might get away with on of the stock or upgraded controllers by getting rid of the thermal pad on the heat sink and using thermal grease when mounting the new controller.

No matter what controller you use, update the amp delivery system. The 13 high current cables, the F/R switch and the solenoid. Of course, they can also be replaced when they fail.