42 Volt Limited Top Speed

[SWFLrunner]

I recently upgraded my '09 PDS cart from 36 to 42 volts.
Save the "you should have just gone to 48" stuff, I get that.
The upgrade included 7 new T 105's, Alltrax 400 amp controller, and solenoid.

I'm extremely happy with the upgrade, I went from a top speed of 16/17 to 22/23, a 35+% increase. I'm not complaining at 23 but was shooting for at least 25. The reason for the 2 numbers is the lower number is flat ground consistent and the higher number is sometimes, like maybe with a little tail wind.

Looking around I have seen people getting higher baseline and significantly higher top end speeds before and after the upgrade so I'm guessing something is holding the cart back some unrelated to the upgraded parts.

Since the upgrade I have checked tire pressure, alignment (set the toe), and adjusted brakes to rule out brake drag. No resulting change.
Battery pack voltage checks out and the batteries are new, cables are stock but don't get hot at all, only the inline fuse that came with the Alltrax gets slightly warm at all. The Alltrax is set up right on the max amps, I am set to Turbo and Street, max speed is disabled (it's pretty flat around here)

If I run the speed calculator I'm spinning the stock 36 volt motor at 5100 to 5300 RPM's on stock 18 inch tires. 20 inch tires are next up and I guess crunching the numbers that it will hit 25.

I guess the question is why doesn't this voltage spin the motor up higher? Where's the hold back? In the motor due to age? something else? This is a pretty simple system there's not a lot of places to look. This is more for my own education more than anything.

Also thanks to Scotty B for the great service.

[scottyb]

Can you ID the cart motor ?
What size tire are you running ? What tire pressure ?
How old are the batteries?

Have you connected a laptop to save a monitor file you can share? I'm wondering what your top rpm is.

[SWFLrunner]

There's no markings on the motor that I can see. I can see the end of the motor and there's a small aluminum plate nearer the transaxle that is worn off or blank.

18 inch tires. I actually also rotated the backs to the front because the fronts were worn from bad previous alignment, the tires on the front are in good shape and uniform. I'm running them at 27 PSI (overinflated) figured that might be holding it back some but not much difference.

I haven't been able to run the monitoring program while running, my personal lap top battery is shot and I need to keep it plugged in. I need to do that to confirm the RPM estimate from the speed calculator.

All bats are brand new.

[scottyb]

New batts are 75% of their potential capacity until well broken in which, according to Trojan, can take from 10-50 cycles.

[cgtech]

True, but new batteries can deliver well over 400a (OP controller size), and their overall voltage is not reduced by 25% when they are new. Voltage = speed.

[SWFLrunner]

Scotty,

Monitored the cart with the rear wheels off the ground.

Batt volts 44.1 full pedal
Motor volts the same
Field Current 2.7 amps
Battery current bounced between 13.9 and 17 amps
Motor current bounced between 14.7 and 15.8 amps
Controller temp 35.3 C

Thought this was strange:
I set the speed limiter at 6500 RPMs and the motor spun up to 6182 to 6194, bounced between these to RPMs

I reset the speed limiter to 7000 RPM'sand the motor spun up to 6619 to 6633.

The controller came set to 6000 max and I have been running recently with the speed limit off.

Also the motor is a stock 36v AMD, tag on the cart body states 2hp. I have the other info off the label I found on the motor if it means anything..

Look normal or like something is off?

[Sergio]

It does not look like the throttle is hitting 100%.

Check the monitor log.

[SWFLrunner]

Controller is reading the throttle at 100% at full push on the monitoring program.

Picked up 1 MPH on the road test now at 23/24 topped out.

[rib33024]

I would not spin those wheels off the ground at 6600 RPM's. Yor motor will fly apart like that

[JohnnieB]

Something is holding your cart back and has been ever since it was in stock form before you upgraded the controller & solenoid and upped the pack voltage to 42V.

In Freedom mode, a stock 36V PDS controller limits the motor to roughly 4400RPM, which is almost 19MPH with stock gears (12.44:1) and stock height (18") tires. However, you were only getting 16MPH, so your tires are only 15.2" tall, OR your differential gear ratio is 14.92:1 (IE: gears from a Workhorse), OR the motor is not receiving full battery pack voltage, OR the motor is sick, OR there is excessive mechanical drag (dragging brake shoes - bad bearings - etc).

Going to an XCT controller will allow the motor to spin at about 5600RPM when powered by a 36V battery pack, which is about 24MPH. Going to a 42V battery pack, ups the speed (and torque) by 16.7% to 6535RPM, or 28MPH.

--------------
Is Turbo turned on?
What Field Map is loaded?

------------
Measure actual tire height. Level on top of tire and yardstick to the ground is close enough.
Then if you can correlate motor RPM and cart speed, we can determine the gear ratio.

----------
Turn the speed limiting on and set limit to 6500.
Turn Turbo on.
Set Speed Sensor to 8-Pole.
---------------
Save a data log from the XCT that include going at top speed on a hard level surface.
Zip it and post it here.

Things I look at are Battery voltage, Motor (Armature) voltage, Motor amps, Field amps, Throttle % and RPM.