EZGO electric Slow up hill

mamonti

Working on a friends 1999 Ezgo electric solid state model. Everything is working well as always except now when he goes up a hill the cart has very little power compared to what it use to have. He bought new batteries since that is what he was told was the problem. Problem is still there. everything checks out ok as to wiring and normal operation on flats, reverse, forward both work fine, acceleration also works fine. I am not sure where it get the added amps to go up hills but I assume the controller. So wanted to touch base and see if you have any other ideas other than replacing the controller? Thanks

BGW

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chloe

You'll get a lot of help, but first the model and drive system are necessary. Does it have a "run/tow" switch on the controller box under the passenger seat?

http://www.buggiesgonewild.com/elect...en-system.html

This info should help

JohnnieB

Welcome to BGW!

Problem could be mechanical. Brakes dragging, dry bearings, things like that.
Or it could be wiring. High resistance in cables, contacts or connections.
Maybe a battery issue (Even new batteries have them)
Could be a controller or that the controller isn't be told to turn on completely (Throttle issues)

Push cart by hand on a hard, level surface. It weighs half a ton, so it'll take a bit to get it moving, but should roll freely once it is moving.

What is the battery pack voltage? (Fully charged should be 38.2V, probably a bit higher since they are new batteries.)

What is battery pack voltage when cart is going uphill? (With new batteries it shouldn't drop more than a volt or so.)

What is voltage between M- and B+ terminals on controller when cart is going uphill. (Should be same as pack voltage when pedal is on floor)
If it isn't the same, there is undesired resistance in the high current circuit someplace.


What is voltage between M- and B- terminal on controller. (Should be nearly zero when pedal is on floor)
(Actually, depending on controller type, it will read from about 0.2V to about 0.5V per 100A of current flowing through controller.)
If it isn't almost zero, the controller is either not being told to turn fully on (Throttle issue) or is being told to and isn't (Controller issue).

Let us know what you find and what type drive system you have and we'll go from there.

mamonti

It is a series type, doesn't have the tow / run switch and the wiring diagram that is exact to what the cart has was from one of JohnnieB posts, it says solid state speed control version from Page N-6 figure N-3. I am not sure what tells the controller to apply more power when uphill however I did put stands under it and the acceleration works as far as the more petal applied the fast the wheels turn. I took it up a hill and it never stopped no matter the grade and another thing I did was stopped it on a hill and then applied the accelerator and it takes off quickly for a second and then crawls. I can push it by hand and when I had it up I checked to see if the wheels / brakes were hanging and they seemed fine. Also when I applied acceleration and left off, the wheels continued to turn for a couple of seconds. I assume it is the controller as the wiring diagram says solid state speed control which again I assume is in the controller however I may be wrong as this is the first time I ever looked at a golf cart! According to the owner everything is working as it always had except for the hills. Looking at the wiring diagram other than the potentiometer which is for acceleration I don't see anything that will provide a signal for hill assist so I figure it is a load measurement in the controller which once reaches a threshold must open a circuit to allow more amps???

JohnnieB

If the cart is a 1999, that isn't the right schematic. That one is for a Marathon with a potentiometer for a throttle.
A '99 would either be a Medalist or a TXT body style. If the body is metal, it's a Medalist. If it is plastic, it is a TXT.
(Also could be a Workhorse or a ST body style)

Plug the serial number in here and it'll tell you what it is: http://www.shopezgo.com/customer-ser...ialNumber.html

Regardless of body style, the attached is probably the correct schematic for it.

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As for the cart slowing down on hills:
There is no "Hill Assist" built into the controller.
In very general terms, what happens is that a Series would motor will accelerate to the maximum RPMs for the voltage applied.
At that point the current flow tapers off to what is needed to maintain that RPM.
In most cases, Series carts use about 50A to 75A when cruising on level ground at top speed.
When the load (Drag) is increased, such as going up a hill, the motor, in and of itself, will start drawing more amps to maintain the max RPM for the voltage applied.
At some point, the controller will reach the maximum amps it will pass to the motor (about 275A for a stock controller) and the cart will slow down.
Also, when a lot of amps are being drawn from a battery, the battery voltage drops, which also lowers the max RPM the motor will reach.

Since the cart stopped performing as well on hills, something changed in the high current circuit.

Weak Batteries could have caused the problem, but replacing them without proving they were the problem, was an expensive "Poke and Hope" by whoever suggested doing so.

Presuming that the new batteries are in the 225AH range and properly installed, as well as having been fully charged prior to first use and subsequently broken in properly to obtain maximum storage capacity, the problem is high resistance in the high current loop, the controller being part of that loop.

Here is a simplified generic drawing of the high current loop. The controller shown is from an earlier model cart, but it works the same.
The same total drive current flows equally throughout the loop and if there is anything wrong with any cable, component, connection or contact, the cart's performance will suffer.

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This is a difficult problem to troubleshoot because the cart is working, but not working right.
The tests I suggested will narrow the possibilities.

Attached Images

	Wiring Diagram - Series.JPG (55.8 KB, 0 views)
	Hi Current Circuit - Series Motor - EDITED.JPG (63.6 KB, 0 views)