2007 PDS 36V Cart w Alltrax XCT400 Slows to 7mph Uphill

[JohnnieB]

Originally Posted by scottyb

Stock tires are 18"

At least that is what is says on the sidewalls, but the actual tire height can vary 1" or more in either direction.

My Carlisle Turf-Master tires are marked 18x8.50-8 but measure a whisper over 17" tall. (17.0395260947761" to be exact. )

[scottyb]

Originally Posted by JohnnieB

At least that is what is says on the sidewalls, but the actual tire height can vary 1" or more in either direction.

My Carlisle Turf-Master tires are marked 18x8.50-8 but measure a whisper over 17" tall. (" to be exact. )

Are you sure ? Mr Carlisle says they are 17.0395260947762

[JohnnieB]

Originally Posted by tulsarust

JohnnieB, you must have been a mathematician in another life! My speed is measured using the Waze app on my phone. The tires appear as lowly golf course turf tires, but I will measure when I get home tonite. Stock white steel wheels with the little plastic spoke hubcaps. We have modded a couple carts for friends with tires and wheels, lights, and rear seats but this one is stock other than a rear seat and the Alltrax XCT.

I appreciate your help and ScottyB chiming in also. thanks

Originally Posted by tulsarust

My reported max speed was 18 on the flat portion; I didn't look at the speed going downhill.

You are right, 6000RPM is the set speed limit.

Batteries were not fresh off of charger. The cart had set for 2 days without a charge since taking it for a spin to attempt datalogs which I finally figured out AFTER reading the Alltrax manual

I use a spreadsheet to view data logs and let it do the number crunching.

The motor is sick or the cart has some stiff bearings someplace. A stock PDS motor can spin at about 5600RPM when turning stock height tires and powered by a 36V battery pack. That translates to 24.1MPH on level ground and as far as I can tell, your cart is only doing about 18.7MPH on the level ground before it started going downhill, where it got up to about 25.2MPH and would have gone higher, except the XCT applied regen braking to keep the motor below the 6000RPM speed limit it was set to.

Does cart push easily (with Run/Tow in Tow, else the Walkaway Safety kicks in and applies regen braking to keep cart under 2MPH).

Has the differently oil been changed. Sludge in pan will add drag to cart.
So will dragging brake shoes and dry bearings.

[tulsarust]

JB, my tires are 17” diameter I’d that helps anything make better sense.

[JohnnieB]

Originally Posted by tulsarust

JB, my tires are 17” diameter I’d that helps anything make better sense.

That helps. Slows the cart speed by about 6% vs motor RPM, but still ought to be reaching nearly 23MPH on level ground.

Also, the 1" shorter than stock tires effectively increases the stock torque by about 6%, so cart shouldn't be slowing as much going uphill.

It's been 8 years since I ran a stock PDS motor with an Alltrax controller (DCX - the XCT didn't come out until 2015) and a 36V battery pack (the batteries weren't all that good either), but if I remember correctly, I was getting a top speed of about 23MPH on level pavement and it only slowed to 17MPH on the steepest hills around here. That is roughly a 25% speed reduction and I'd expect something in that same ballpark for your cart, so if it does 18MPH on level ground it ought to do about 13MPH going uphill.

Of course there are a ton of variables not being taken into account.

[JohnnieB]

Originally Posted by scottyb

Are you sure ? Mr Carlisle says they are 17.0395260947762

On his website, Mr. Carlisle says they have a MTD (Mounted Tire Diameter) of 18.3", which is 2.26" off the true diameter. The sidewall markings are closer and they are 1.04" off.

In a nutshell, the only way to know for sure what the height of your cart's tires are, is to measure them.

-------------
I believed the numbers on the Carlisle website until I got an XCT which has motor RPM data. My cart speed vs motor RPM calculations weren't coming out right and I eventually realized the tire height was over 2" off, so I measured them.

[tulsarust]

So, something isn’t jiving w this motor compared to a good stock motor. My options are replace the motor for $500 or crack this one open and see if brushes, bearing, or armature is bad?

[JohnnieB]

Originally Posted by tulsarust

1. So, something isn’t jiving w this motor compared to a good stock motor.

2. My options are replace the motor for $500 or crack this one open and see if brushes, bearing, or armature is bad?

1. Yes.

2. That sums it up pretty well.

[tulsarust]

After cooking 30 pork butts to feed 500 people at church this weekend I’ll see if I can muster up enough energy to peak inside the motor and see what gremlins lie within. Thank you for supplying some technical wisdom!

[JohnnieB]

Sounds like a plan.

Be sure to use a second wrench on the bottom nut when taking the motor cables off the studs. If the stud turns, bad things can happen inside the motor.

Also, check the resistance between the studs on the motor after the cables are removed. Carbon dust get all over everything inside the motor and is conductive, so the amps have an alternate path through the motor, bypassing the windings.

With cables disconnected:
A1 to A2 should be between 0.3Ω and 1.0Ω.
F1 to F2 should be between 1.0Ω and 2.0Ω.
A1 to F1 should be between OPEN.
F1 to motor case should be 5,000,000Ω or higher.

Take pictures of motor's innards.