HELP! 98 EZGO TXT 36v - Low Torque & Low Top Speed

[offthemap]

It's a long read but I've tried to set out as many details as I could in my first pass

Intention: I'm building/repairing a recently purchased golf cart with the intention of using it primarily as a hunting buggy first and a neighborhood cruiser second, but I'm having serious issues with my top speed & uphill torque. I don't need to break the sound barrier or climb a pine tree, but it bugs the heck out of me to know that there is some issue that's going un-resolved and it's keeping me from doing the most important upgrades like a motor or going to 42 volts.

I am already over-spent on this cart at $3200. So, I need to diagnose my problem on my own without just throwing parts at it or putting it in the shop ...and before my blonde, live-in "accountant" puts it on the curb with a for sale sign. Haha. Just kidding, kinda.

There are more things that I want to the cart to increase performance (like add a battery & cables & 42v charger, and do the Plum Quick Bandit motor upgrade) but before I do I need to get it "up to par", or to where it will at least perform at an adequate level.


Here are my specs:

- 1998 EZ-GO TXT 36v (series)
- Alltrax Axe 4844
- 6 x T105's purchased a month ago and they currently have less than 20 charge cycles
- 2ga Silver soldered cables throughout
- 36v/48v Super Duty Solenoid 400a/1000a
- 22" A/T Tires
- 6" Lift - Rear Seat Kit - Winch Bumper - Clays Basket - Riding Topless
- 36v / 5a EZGO charger


My Issue: My cart has no mechanical drag and has been upgraded as referenced above, HOWEVER, it will only reach a top speed of 13-14 mph on flat ground & slows to a crawl at 8-9 mph while climbing neighborhood hills that aren't that steep.

With a stock motor (series 36v), no brake drag, 400a controller, and properly inflated 22" tires, shouldn't I be running at a top speed more than 14 mph on flat ground and maintaining a higher MPH on the hills? Shouldn't it be somewhere around 18mph top speed and 14 mph under load uphill?

It's not is not that I feel like I'm missing the additional performance for what I think I should be getting with my upgrades, its that I feel like I am not even running at a level equal to stock, or OEM level, performance from a cart that has been upgraded.


What I am concluding so far: Alright, well I have run some tests and they are leading me to think that either my controller is going bad OR my ITS is going bad OR I need to re-crimp all of my cable ends. (Caveat: I've checked the cables over and over and they all appear fine mechanically speaking. Each one is soldered and heat-shrinked already so if I did crimp them again it would be just for peace of mind and/or to remove another variable that is causing my issues).

I hooked up my laptop into my Alltrax Axe controller and adjusted my settings to insure that I was delivering 100% of the capable amperage output to the motor and that the throttle was set to 100%. I also set my throttle response to “S curve”. Once I set everything properly, I put the seat back on, placed the laptop on the seat next to me, opened up the “monitor” tab in Controller Pro, selected every gauge, selected the “continuous interval” and then drove the cart around the block and up a very mild-grade hill (on pavement). I basically ran it at wide open throttle the entire time.

Here are my first-run results from the Controller Pro software:

Testing the ITS:

I didn’t actually pull the floor up to examine if the ITS plunger was protruding 1/4" past the "donut" at WOT, but the tests below showed I was getting/giving 100% throttle. Controller Pro showed a 100% throttle readout with no hesitation. The monitor/gauge fluctuated in direct correlation with my pedal position;

1. I’d like to know if ya'll think if that is enough of a test to determine that the ITS box is operating as it should, or if it could still be the problem? For example, if the ITS plunger is only going to 80% throttle, or so, mechanically at the box, would the controller even be able to determine that it was less than 100% or would it operate as if it was getting 100% of the available throttle from the pedal?

2. Is this gauge reading a representation of the percentage of the throttle output as set by the user thru programming the controller? In which case could read 100% even if the ITS plunger only went to 80% mechanically speaking, right?

OR

3. Is this reading in Controller Pro a measurement of the actual percentage of throttle delivered from the pedal & ITS and received by the controller?

Testing controller function / battery pack quality:

- 37.4v – Resting/Beginning Voltage - Pack voltage resting before I ran any tests. It has been sitting for 4 or 5 days without a charge. The pack is good;

- 34.4v(ish) – Voltage Drop Under Uphill Load – This is what my pack read (real time #’s) while going up the mild-grade hill. It fluctuated some but this was the lowest I saw. This appears to be within spec;

- 140 amps – Readout for “OUTPUT CURRENT” & “BATTERY CURRENT” under peak load driving uphill. This was the maximum amount of amps at any point during my testing;

1. Does this mean my controller is going bad? I feel like this is my main question / concern right now.

Testing battery pack quality AFTER full charge:

After the run & testing with controller pro, I parked the cart and plugged in my 36v / 5 amp charger and left it plugged in until it automatically shut off apx. 2 hours later. (I know, I know. I need a DPI Charger! and I will upgrade to a 42v DPI as soon as I can find my problem ) Then, I used my DVM and came up with a few more readings:

- 39.1v - Resting Voltage immediately after full charge.

- 38.6v – Resting Voltage 2 hours after full charge. This was when I used the DVM and ran the tests below. This appears to be within spec for the timing;

- Each individual battery tested at: 6.4v, 6.4v, 6.3v, 6.3v; 6.2v, & 5.9v; These were random and came in no particular order but they only total 37.5v??;

- 38.6v – With the key “ON”, I put my DVM leads on the B- and M- posts on the controller and depressed the pedal until the LED came on. I got a reading of 38.6v;

1. This should tell me that I don't break or issue in the main "loop", right?

- I also tested the solenoid based on the instructions on BGW. I don’t remember what the exact readings were but I do know that I determined that the solenoid was good;

I intend to do all of these tests again tonight (at FULL charge) to delineate any variables and run a few more tests once I can get it up on blocks and effectively go through all of the diagnostic steps that ScottyB has so graciously set out for us that are golf cart challegened.

[scottyb]

Simply put, the motor does not have full access to the battery pack. 400a is restrictive for a series cart with big tires and rear seat. Especially off road.

Additionally, 5 amps is not enough of charge to keep your batteries in good condition long term. 10% of Amp hour capacity is needed for proper charging.

[cartattach]

I disagree with above. I have friends with a 4844 running almost 30mph. That controller is extremely capable. The series motor isn't all that great to begin with, and the biggest controller on earth won't make it any faster. 15mph is about what a series cart runs. Get a better motor, like an ES52 type for offroad and you should get 18-20 mph plus be torquey.

[JohnnieB]

Sounds like you have a 36V Series drive with 22" tires and might be a bit on the heavy side. (Rear seat. winch, Clays basket, Etc.)

A typical 36V series drive on stock height (18") tires does about 14 MPH, so with 22" tires it should do about 17 MPH, mathematically.
Sounds like you have good batteries and good cables and you say it doesn't have brake drag, so I suspect you have tires whose max inflation pressure is 10 PSI or less.

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The percent throttle is actually the percent duty cycle of the PWM output to the motor.

When the Output Current and Battery Current read exactly the same amount, the controller is wide open.

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The number of amps a motor can draw depends on how fast the armature is spinning. I suspect the motor was spinning at 1500 RPM (about 8 MPH on 22" tires) when it was drawing 140A. Your stock motor might be able to draw all the amps the 400A controller will pass when starting from a standstill, but the amps will drop off fairly quick as the cart accelerates through walking speed and beyond.

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I don't like the battery that has a 5.9V reading while the others are all 6.2V or higher. A bad battery can cause problems like you are having.

Measure and record the battery voltages when they are fully charged.
Drive cart 4 or 5 miles, let the batteries rest for half an hour and then measure and record the battery voltages again. They should all six loose the same amount of voltage.

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When you do your testing with the laptop attached to controller, have Controller Pro save the data file on the laptop. Then it can be reviewed after the fact.

[JohnnieB]

Originally Posted by cartattach

I disagree with above. I have friends with a 4844 running almost 30mph. That controller is extremely capable. The series motor isn't all that great to begin with, and the biggest controller on earth won't make it any faster. 15mph is about what a series cart runs. Get a better motor, like an ES52 type for offroad and you should get 18-20 mph plus be torquey.

I believe you missed the purpose of offthemap's post.

He is trying to find out why his cart isn't doing the 17, or so, MPH it ought to be doing with 22" tires.

Once he does that, he is planning to up the pack voltage and upgrade to a different motor.

[scottyb]

Originally Posted by cartattach

I disagree with above. I have friends with a 4844 running almost 30mph. That controller is extremely capable. The series motor isn't all that great to begin with, and the biggest controller on earth won't make it any faster. 15mph is about what a series cart runs. Get a better motor, like an ES52 type for offroad and you should get 18-20 mph plus be torquey.

Speed and torque are 2 different things. Call the man who makes the Engineering Sample motors and ask if it will perform well with rear seat, 22s, off road and 400a control.

[cartattach]

Originally Posted by JohnnieB

I believe you missed the purpose of offthemap's post.

He is trying to find out why his cart isn't doing the 17, or so, MPH it ought to be doing with 22" tires.

Once he does that, he is planning to up the pack voltage and upgrade to a different motor.

I believe you are correct. Though I have had the old series before, and 17 while possible mathematically, didn't happen in reality. Fact is, the series setup just sucks for speed bar none. Having friends running the same setup except with 23' tires and speed motors on one, and a 7126 motor on the stock size one, I can say that the 400 amp alltrax will run just as well as the 650 amp alltrax. We put two identical carts up against one another, one had the 400 and the other the 650. They performed identically, the 650 offered no further gain in performance. They both ran 28mph on flat road, and well over 30 downhill if you were so brave to do it.

Also, I concur with your opinion on the 5.9 battery. I admit I skimmed his post the first time as it was long and I was running short on time. What I saw that I didn't agree with was the thought that a 400 isn't enough or somehow a larger controller would make any difference on that stock motor, as we all know it wouldn't. The batteries need to load tested and the 5.9 is likely the culprit. I would nearly bet the farm on that.

[cartattach]

Originally Posted by scottyb

Speed and torque are 2 different things. Call the man who makes the Engineering Sample motors and ask if it will perform well with rear seat, 22s, off road and 400a control.

I am well aware of the difference in torque and speed motors. The OP said hunting buggy first, thus his need for an ES52 type torque based motor which will still achieve about 18mph for his secondary use of street cruising.

[offthemap]

Thanks for the input guys.

[offthemap]

Originally Posted by scottyb

Simply put, the motor does not have full access to the battery pack. 400a is restrictive for a series cart with big tires and rear seat. Especially off road.

Additionally, 5 amps is not enough of charge to keep your batteries in good condition long term. 10% of Amp hour capacity is needed for proper charging.

I understand that I shouldn't expect to gain any top end with my setup if I were to add the Axe 4844 right now, but is it normal for me to be seeing nearly 50% less speed on mild hills in my neighborhood?

What about the amperage readout? I NEVER saw it get above 140a at any point in my run. Therefore I'm looking at this as if my controller isn't capable of allowing/giving the 400 amps it's rated for. Am I wrong about that logic? (I hope I am!)