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Electric EZGO Electric EZ GO Marathon, Medalist, TXT and RXV.



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Old 10-04-2016, 08:23 AM   #1
TappanDan
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Default EZGO 36v goes real slow

I have a 1994 EZGO Medalist 36v. Bought it 2 years ago and it ran well, maybe 10-12 miles an hour. Enough, at least, to scare my wife going downhill or around corners :-). Now, it moves very slowly, especially uphill it just crawls. On a flat it will go only about 5-6 mph, about a fast walking pace at best.

This started after I replaced the F/R switch. One of the cable connections had corroded and broke off. The nut was seized onto the post and it twisted off trying to remove it, so I had to replace the whole switch. I crimped a new end on the cable, which is pretty solid.

The only difference before/after F/R replacement, beside the crimped end, is that I did not reinstall the reverse beeper. But I can’t imagine that would be the cause.

Batteries are fully charged, charger ran for 17 hours. Six batteries voltage is: 6.75, 6.65, 6.75, 6.89, 6.87, and 6.77. Electrolyte is covering the plates. I also used a load tester and they all tested ok. (On this note, I’ve seen someone say you need a 350 amp carbon pile tester, not a 50 amp tester. I have a 50 amp tester, which puts a load on it while you hold the button for 10 seconds. This thing shows batteries are all good, but again, I don’t know why I should not be using it. This is what I have: https://www.amazon.com/Schumacher-BT...battery+tester)

I’ve read a lot on this forum about speed sensors causing this type of problem, but I don’t know if this model even has one.

The only thing I can think of is to replace the cables, but it just doesn’t seem like that could make *that* much difference. They do get pretty hot going uphill, though. But I’m not sure how hot is too hot.

Any clues would be much appreciated!
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Old 10-04-2016, 09:00 AM   #2
JohnnieB
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Default Re: EZGO 36v goes real slow

You have a series drive (series wound motor), so it wouldn't have a speed sensor.

To get "at-rest" voltages off the batteries, you have to let them rest (no charging or discharging) for about 12 hours after the charger shuts off automatically. After the rest period, your 36V battery pack ought to read 38.2V and each battery should read 6.37V and all six should be within 0.1V of each other.

The good/bad scale on the automotive type load tester you have isn't calibrated for deep-cycle batteries and 50A is a relatively light load, so batteries that would fail a 350A load test may test good. Your cart is a more effective load tester. Connect a DVM to the pack and see how much the pack voltage drops going up a hill. If it drops lower then about 32V, check the individual battery voltages. They all should drop about the same and if one (or more) is dropping significantly more than the others, it is probably bad.

Sounds like you need a new set of high current cables whether the batteries are good or not. Too hot for the cables is anything more than about 10°F above ambient air temperature climbing steep hills.

Replace all 13 (or 14 if the controller has an A2 terminal) high current cables with 4Ga or thicker.

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To check for excessive resistance (power loss) in the high current cables, connections and F/R contacts, connect a DVM between the B- and B+ terminals on the controller and note the lowest voltage reached while climbing a hill. It should closely match the lowest battery pack voltage reached climbing the same hill. The difference in the two voltages is the power loss in the high current cables, connections and contacts.
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Old 10-04-2016, 09:49 AM   #3
TappanDan
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Default Re: EZGO 36v goes real slow

Johnnie, thanks for detailed reply. It all makes perfect sense.

I'll be able to perform these tests this weekend so I'll post my results.
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Old 10-04-2016, 10:34 AM   #4
JohnnieB
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Default Re: EZGO 36v goes real slow

If you have a DVM with a min/max function, finding out what the voltage drops to is easy.


Here are a couple manuals that might help some.

A series drive cart is called "Non-DCS" in the service manual.
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Old 10-04-2016, 03:47 PM   #5
TappanDan
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Default Re: EZGO 36v goes real slow

Nice manual! I had trouble finding parts blowups when I was replacing that F/R switch. This is great!
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Old 10-29-2016, 08:44 AM   #6
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Default Re: EZGO 36v goes real slow

Ok I tested the voltages of the battery pack under load, going up a slight incline. I also tested each individual battery. The pack was 38.4v when stopped, and dropped to 34.6v on an incline. All the batteries tested at 6.2-6.4 when stopped, and 5.7-5.8v on an incline. I don't think that's too bad, at least not bad enough to cause this whole problem.

I found another device, I've attached a couple of pics. From the manual it looks like a solid state speed control. I know you thought I didn't have one because of the motor type, but could this thing be causing my problem? I know I should replace the cables with heavier gauge because they heat up, but they were fine for years, so I don't think they caused this problem.
Attached Images
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File Type: jpg Golf cart electrical2.jpg (219.5 KB, 0 views)
File Type: jpg Golf cart electrical3.jpg (222.4 KB, 0 views)
File Type: jpg Golf cart electrical4.jpg (222.9 KB, 0 views)
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Old 10-29-2016, 09:52 AM   #7
JohnnieB
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Default Re: EZGO 36v goes real slow

I knew your cart had a speed controller. I said it didn't have speed sensor.

A speed sensor attaches the motor and tells the speed controller how fast the armature is spinning. EZGO doesn't use Series wound motors with speed sensors and didn't use them with SepEx motors until they introduced the PDS drive system in 2000.

-----------
Let's find out if the problem is the amp delivery system (battery pack, high current cables and connections) not delivering full power to the speed controller, or if the speed controller isn't passing it along to the motor. (There are other possibilities, but that ought to point us in the right direction for further troubleshooting.)

It will take three separate voltage measurements while cart is traveling at max speed over the same stretch of a hard level surface.

1. Connect you voltmeter between the M- and B+ terminals on the speed controller. (B+ terminal has two heavy cables connect to it in your pictures. B- terminal has one heavy cable and one small wire connected to it, M- terminal only has one heavy cable connected to it) What is the voltage at max speed?

2. Connect your voltmeter between the B- and B+ terminals. What is the voltage at max speed?

3. Connect your voltmeter between the battery pack's main positive and main negative terminals. What is the voltage at max speed?
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Old 10-29-2016, 02:07 PM   #8
TappanDan
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Default Re: EZGO 36v goes real slow

Quote:
Originally Posted by JohnnieB View Post
I knew your cart had a speed controller. I said it didn't have speed sensor.
Sorry, the subtle difference escaped me!

I performed the tests, pedal floored on level hard ground:
M- and B+: 21.7v
B- and B+: 32.6v
Main battery pack: 33v

The readings fluctuated a little during the tests, maybe 3 or 4 tenths of a volt. But those readings were the most steady.

Really appreciate all your help!
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Old 10-29-2016, 03:45 PM   #9
JohnnieB
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Default Re: EZGO 36v goes real slow

It takes a while to learn what cart has what stuff in it and what that stuff is commonly called.


B- and B+: 32.6v & Main battery pack: 33v, so your cables, connections and contacts are only losing about 0.4V. That isn't too bad, but I would replace all 13 high current cables with 4Ga or thicker at some point in time not too far in the future.


B- and B+: 32.6v & M- and B+: 21.7v while pedal is on floor, so the controller is only passing about 2/3 of the applied voltage to the motor. This is why your cart is running slow.

Series type controllers usually give up the ghost completely rather than partially die, so I suspect a throttle issue, or the orange wire that went to the same switch as the reverse beeper got connected wrong when you replaced the F/R assembly.

The orange wire is 1/2 speed reverse. When the F/R is in R, battery pack voltage is applied to Pin-3 in plug on top of controller (via the orange wire), telling it to run at half speed, which is about what your cart is doing.

What is the voltage on Pin-3 when F/R selector is in forward? (should be zero)

Note: To measure voltages on the pins, push test probe tip into the backside of the plug while plug is installed on controller.

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To check the ITS (throttle), connect the negative test lead to the battery pack's main negative terminal.

Jack up rear wheels and put on jackstands so half ton cart doesn't take off unexpectedly and run over someone or something.

Measure voltage at Pin-2 (Black wire). Should be slightly above 14V, but less than 15V.

If that is good, measure voltage at Pin-1 (white wire)

When pedal is pushed just far enough to make solenoid click, the voltage should be 0.45V to 0.53V. If so, press pedal slowly to floor and voltage should smoothly increase to 1.5V.

----

BTW: There is an inline connector in the multi-wire cable coming out of the pedal box that cause all sorts of problem when it get damp. Find it, disconnect it, clean it and reconnect it.
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Old 10-29-2016, 05:31 PM   #10
TappanDan
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Default Re: EZGO 36v goes real slow

First thing I thought of was the orange wire you mentioned. I could very well have hooked that up wrong. But I have before and after pics and they look ok.

I'm not sure which one is Pin-3, so I measured voltage at that orange wire terminal. i circled it in the pic. Voltage was 35.8v in both F and R. It doesn't seem to matter whether it's plugged in or not. I could clip the alligator clip right on the tab, with the wire half on or all the way off. (I don't have pointy probes, have to get some.)

The blue-ended cable is the one I had to replace. In the first pic, it's not hooked up, so don't worry about that cable.
Attached Images
File Type: jpg F-R After replacement.jpg (56.6 KB, 0 views)
File Type: jpg F-R Before disassembly1.jpg (98.2 KB, 0 views)
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