Range and speed troubleshooting help

[checkoutmyjunk]

I am breaking this question out from my build thread to see if I can get more focused help

The range and speed of my cart does not match my expectations.

On the flat I am seeing 8mph with up to 10 if there is a slight decline in the road.

On fairly seep hills I am am seeing 4-6mph

I am down to 3 potential problems:

Motor:
Is it possible that it's drawing more current than it should? How do I test for that?
What am I not considering with the motor that could cause range and speed issues

Controller:
Is is possible that the controller is drawing more current that it should? How do I test it?

Expectations:
I was hoping for 15 mph and a 15 mile range, being that the manual states the speed is within OEM spec I don't think my expectations are too high.

As a qualifier I would like to cover some of the trouble shooting I have completed on the cart:

• Placed the cart on a lift and verified that all 4 wheels have no drag
• Checked all electrical connections with a IR heat gun
• Replaced all "power circuits" with 2awg leads
• Eliminated the F&R Switch with a 400A reversing contactor
• Inflated all tires to maximum PSI
• Performed most of my testing on paved roads

List of hardware I am working with.

New Trojan T-105s
48V
955E shuttle
Stock wheel height (18.5")
73233-G01 "Solid State HDI Controller, 350 amp rated"
"CH7-4002 Advanced D.C. Motors Inc. "Heavy duty, 48 volt DC, high efficiency series wound, brazed armature, solid copper windings, vented, 5.5 hp (4.0 kw) at 1980 rpm"
OEM Gears "High efficiency differential with helical gears, 14.78:1 ratio"
This cart is about 1000lbs with the batteries
Leaf springs front and rear

[checkoutmyjunk]

Did some maths

With a 18.5" OD tire, and 14.78:1 differential @ 1980RPM (motor rating per the spec in the service manual) I should be seeing 7.4mph as I calculated it.

That leaves two questions:

The service manual states 5.5hp @ 1980rpm, is that the max rpm I can expect on flat ground?

Why does the manual state 12 - 14 mph when that appears to exceed the mechanical limits?

[DaveTM]

A couple more details and some clarification may be needed:

#1--What temperature are you driving in? (Your ambient temperature outside?)

#2--I don't have the service manual, but you state the service manual says you should be seeing 7/4mph, the in the next sentence you state the service manual states 12-14mph. Which one is correct?

[cgtech]

The 14.78 gears is a hint, I bet that's why it's slow. And I bet the 15mph was referring to ezgos with the standard 12.55 axle ratio.

[checkoutmyjunk]

Originally Posted by DaveTM

A couple more details and some clarification may be needed:

#1--What temperature are you driving in? (Your ambient temperature outside?)

#2--I don't have the service manual, but you state the service manual says you should be seeing 7/4mph, the in the next sentence you state the service manual states 12-14mph. Which one is correct?

1. I am seeing between 50 and 75F here in central PA

2. Sorry for the confusion, I was referring to the motor rpm and HP rating with that note in parentheses ().

[checkoutmyjunk]

Originally Posted by cgtech

The 14.78 gears is a hint, I bet that's why it's slow. And I bet the 15mph was referring to ezgos with the standard 12.55 axle ratio.

Interesting, are you suggesting that they misprinted the manual? The speed and transaxle ratio are on the same page right next to each other. Wouldn't that be a hummdinger!

I recalculated with a 12.55:1 ratio and it only ups the top speed to 8.7mph @ 1980rpm with a 18.5" tire OD. This tells me that I am not seeing my max HP up hill as I am not able to attain 7.4 in an uphill driver only test.

I think what I am learning here is my motor is not spinning fast as it should, even if my final drive is lower! I Guess a differential inspection in oil change is in order next to see if I have any glitter in there. If the rear checks out I am back to motor or controller again.

[checkoutmyjunk]

I suspect that I am taking the rating from the manual (5.5hp @ 1980rpm) and using it as a max rpm and that that is wrong. If I am applying 50V to that motor under a normal load should I see more than 1980 rpm? The cart has a bit of spunk from 0 to say 4mph. On one occasion it even spun a tire on wet asphalt with a stab of the go peddle.

I tried to call the manufacture of the motor to verify. The nice guy that picked up the phone said that they were bought out and now Nidec motor. When I called Nidec motor's customer service line they stated that they no longer make dc motors nor do they support them.

At one point in my research I ended up at Plum Quick Motors and they suggested I try the black widow. When I called them today to see what the max RPM on the Black Widow was, I was told "6500......I think". If I use the same calculations, I could see a theoretical 24.2mph with zero load.

I am starting to feel like a dog chasing it's tail.

[JohnnieB]

The only significance of the 1980RPM mentioned in the motor's specs is that was how fast it was spinning when it was producing the stated HP and HP is pretty much a rubber yardstick and is the calculated result of multiplying the RPM by the torque developed at that RPM and dividing by 5252.

How fast a DC traction motor will spin is determined by the applied voltage vs the mechanical load being placed on the motor. How fast the cart can go is determined by the maximum RPM the motor reaches with the given voltage and given drag, times the transaxle gear ratio and the tires height.

For starters, the 18.5" tire height is approximate at best and can be off more than an inch in either direction, so get out a yardstick and a level and measure the true height. (My tires are marked 18", but are only 17" tall)

Also, we don't know if the controller is going to 100% throttle or what the battery pack voltage is dropping to under load.

Connect a DVM between the controller's B- and B+ terminals and measure voltage applied to controller at top speed on level pavement (should be same as pack voltage under same load, if not fix it). Then connect DVM between the controller's M- and B+ terminals and measure voltage applied to motor while at top speed on same stretch of level pavement.


Plus, what is exact year and exact model number of cart?

Also, disconnect the orange wire from the controller (1/2 speed reverse) to see if makes a difference.

[checkoutmyjunk]

Originally Posted by JohnnieB

The only significance of the 1980RPM mentioned in the motor's specs is that was how fast it was spinning when it was producing the stated HP and HP is pretty much a rubber yardstick and is the calculated result of multiplying the RPM by the torque developed at that RPM and dividing by 5252.

How fast a DC traction motor will spin is determined by the applied voltage vs the mechanical load being placed on the motor. How fast the cart can go is determined by the maximum RPM the motor reaches with the given voltage and given drag, times the transaxle gear ratio and the tires height.

For starters, the 18.5" tire height is approximate at best and can be off more than an inch in either direction, so get out a yardstick and a level and measure the true height. (My tires are marked 18", but are only 17" tall)

Also, we don't know if the controller is going to 100% throttle or what the battery pack voltage is dropping to under load.

Connect a DVM between the controller's B- and B+ terminals and measure voltage applied to controller at top speed on level pavement (should be same as pack voltage under same load, if not fix it). Then connect DVM between the controller's M- and B+ terminals and measure voltage applied to motor while at top speed on same stretch of level pavement.


Plus, what is exact year and exact model number of cart?

Also, disconnect the orange wire from the controller (1/2 speed reverse) to see if makes a difference.

Thank you JonnieB, you have given me a big enough bite of information to chew on in the evenings!

I assumed 1980RPM is where it either made peak HP or was the engineer's desired value so they shut the test down after that. I have had enough cars on the dyno to not put too much faith into HP figures.

Drag alone could have been a guess, but max RPM at a specified voltage has to be accurate to gauge the motor in this regard. I was hoping that the now defunct manufacture of the motor could have helped in this fuzzy math, oh well there are more accurate ways to skin this cat.

I also know about tire heights from tinkering with cars. I should have qualified that before I spouted off here in the form!

Trey from EZGO sent me a 3rd manual, a 160+ pager that covers how to test the controller. I picked up a voltage meter to install on the cart, hopefully that will give me a better picture. I will report back with my findings under load.

EZGO Shuttle 955E made in 2001

I have not made it out to the garage since I posted but I do recall seeing a orange wire and a few that looed like generic insulated crimp connectors that leads me to believe that this might have been jimmied in the past. - What a simple solution this could be!

[JohnnieB]

Yell if you need me.