1994.5 EZGO Medalist No Torque

[bkoether]

Hey all, I'll try and make a long story short for quick help. Had the 1994.5 EZGO Medalist for a couple years now. I live in a really hilly area so when I bought it I upgraded the motor to a 8hp +40% high torque D&D motor to help with the hills. When I installed it I never really gained any torque and assumed it must be a bad controller so have just dealt with terrible performance the last two years. Finally upgraded everything the last week to new batteries, HD F&R, 2ga cables, Alltrax SR48600, MZJ400A solenoid and to my bitter disappointment it didn't help with the torque issue whatsoever.

My question is, what am I missing? The only thing I can think of is the motor is somehow defective? Is there something that could have been a manufacturer defect in the motor that would allow it to work but work poorly? Since I have the Alltrax now I can see the amps while running. When I was limping up a steep hill it was only pulling between 100-150amps.

I've learned a lot about carts in general over the last couple years but am still not real familiar with how the inner workings of the motors function so any insights or help is much appreciated. Thanks!

[ojo]

One thing... is the Alltrax prepared with the correct field map for your motor?

[Reddawg454]

Series carts don't use a field map.

[ojo]

OK, sorry

[JohnnieB]

Are you running a 36V battery pack?
What did the battery voltage when the 100 to 150 amps where being drawn on the hill?
What is the tire height?
What is the max inflation pressure of the tires?

An electric motor's ability to draw amps decreases as RPM increase and the torque produced by the motor is determined by the amount of amps the motor is drawing. The max RPM a motor will spin at for a given voltage applied is reached when the amp flow through the motor is producing an amount of torque that is equal to the mechanical load (drag) on the motor. When a cart starts going uphill, the mechanical load increase and the motor slows until it is physically capable of once again drawing the amps needed to produce the torque equal to the new mechanical load.

Series drives slow the most on hills, Sepex drives do better on hills and AC drive are the least effecting by inclines.

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I suspect your cart has tall, low pressure tires since you live in a hilly area.

[bkoether]

36v, tires are 22x11-10, has lift kit, voltage is reading 38.2 upon starting, drops to about 35 on hills at 140-150amps, running about 14psi in tires.

I just find it hard to believe that this is as good as it gets (barely crawling up hills) with the highest torque motor I could find and the biggest controller. If the best anyone can do is 150amps why are they even selling a 600amp controller? Appreciate any ideas about what could be wrong.

[ojo]

I'm sure JohnnieB will explain what's really wrong... stock tires are 18" tall, with 22" tall tires you'll lost all the torque which the high torque motor provides and a controller didn't make amps.

[bkoether]

I guess what would be really helpful is if someone on here has a similar set up/motor and can tell me what kind of amps/voltage they’re pulling on hills. My motor is a D&D 170-004-0001 8hp high torque (+40%). Thanks.

[JohnnieB]

A series drive cart with a high torque motor and 36V battery pack isn't going to be a speed demon on 22" tires. My guess is about 14.5MPH top speed and slows by up to about a third on a mild incline (5°) and up to two-thirds or more on the max recommended incline of 14°.

If you went to 48V, it would up the top speed by about 5MPH and reduce how much it slowed on hills.

What is your top speed and what does it slow to on hills? (and how steep are the hills - chart attached)

As for why 600A and larger controllers are available, some electric vehicles have motors that can draw that many amps. One thing to remember is electric motors can only draw high amps when they are turning at low RPM, so above a certain RPM it doesn't matter how many amps the controller can pass, the performs will be the same. In other words, controllers with a higher amp throughput have roughly the same performance at top speed as controllers with lower amp throughput.

Another thing to remember is controllers are valves, not pumps. They can only limit the number of amps the motor is allowed to draw. The motor's RPM determines the number of amps that specific motor can draw.

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If possible, record a datalog from the SR controller, showing running at top speed on level ground that transitions into an incline. You'll have to ZIP the .csv file to attach it.

[bkoether]

Awesome info, thanks! I’ll try and get that recording and post for evaluation.