EZ-go electric cart question

My wife is about to kill me. We have an '03 36V electric EZ-Go for her
excursions around the property.
It's developed a "no climb" problem. With the throttle down, the cart
goes about 1/4 speed on flats, and won't climb a 2% grade.
It's accompanied by a near-silent gentle vibration. Close listening
discovers that the motor is running full-speed, but the wheels aren't.
I took off both rear hubs and inspected the splines. I've seen them go
on EZ-Gos before. But they were fine, and that problem is usually
accompanied by a fairly loud growling noise.
The motor input/diff-case is a unitized, sealed affair, and I cannot find
any drawings for it -- electric cart, not gas; found the gas diagrams.
There _may_ be a belt inside the case, or a clutch to prevent overloads.
This feels just like a slipping friction element. But I have to pull the
whole rear axle assembly and both axles from the case to do that
inspection -- ain't a small job. So I'm looking for hints first before I
shoulder into that job.
On-line help is scant except for one site that is down right now.
Has anyone here seen this problem specifically on an electric EZ-Go?
Lloyd
Reply to
Lloyd E. Sponenburgh
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Is the manual any help?
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says sometimes the brakes lock up on those.
--Winston
Reply to
Winston
Winston fired this volley in news:jsd7e81uo4 @news1.newsguy.com:
I have it. No. They do not show an exploded view of the transaxle. It's considered a "replacement item" only.
It's not locked brakes, either. Had both drums off to inspect the hub splines.
LLoyd
Reply to
Lloyd E. Sponenburgh
"Denis G." fired this volley in news: snipped-for-privacy@3g2000vbx.googlegroups.com:
Yes, thanks. I've been looking for that all day. There are no friction elements or drive belts, so it's obviously not a tranny problem -- no grinding noises.
Since the motor sounds like it's running, I'm next going to suspect that it's an electronic problem with the controller that is "ringing" the windings without actually making it go.
I've got a 'scope. Next check is electronic. Batteries are good.
Lloyd
Reply to
Lloyd E. Sponenburgh
"Pete C." fired this volley in news:4fea4649$0$14540 $ snipped-for-privacy@newsreader.readnews.com:
Didn't, actually, Pete. I got the wrenches out right after I posted. It takes a while just to get down to the motor/tranny.
I can chock the machine and put it in forward, and the motor sounds like it's running, but it doesn't have enough torque to move against the chocks.
Hmm...
LLoyd
Reply to
Lloyd E. Sponenburgh
Bypass the controller and see what happens. Put jumper cables from one 12 volt battery to the motor directly - motor should run. If id doesn't you have motor trouble. If it does you have controller or battery/cable problems. My bet is on a blown controller.
Reply to
clare
If you jack up one wheel how easy is it to turn by hand? Does it spin the motor?
jsw
Reply to
Jim Wilkins
"Jim Wilkins" fired this volley in news:jsdr2n$hfk$1 @dont-email.me:
If I jack up both, you can see that the diff works. If I jack up one, I can turn it pretty easily, but it's only 6:1 to the motor. You cannot see if the motor is turning. It's a DANA tranny, and the motor mounts entirely into the tranny case input side.
LLoyd
Reply to
Lloyd E. Sponenburgh
snipped-for-privacy@snyder.on.ca fired this volley in news: snipped-for-privacy@4ax.com:
Yup. Only way to "bypass" on this machine is to disconnect both the field and armature connections and do it manually. Tomorrow. It took me a while this afternoon just to get to the motor -- taking off accessories, bag holders, baskets, body panels...
LLoyd
Reply to
Lloyd E. Sponenburgh
Another possibility is the motor coupling to the transaxle is slipping. Art
Reply to
Artemus
snipped-for-privacy@3g2000vbx.googlegroups.com:
If you don't have it, there's another manual on this page:
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--> Technician's service and repair manual electric carts
Diagnostics on pg 74 (F-8) indicate that it might be a problem with the speed sensor (fault).
Reply to
Denis G.
"Artemus" fired this volley in news:jsdsmu$oah$1 @dont-email.me:
There is no such. There is a heat-shrink-fit spline coupler on the nose of the motor shaft that engages a splined shaft on the input side of the transmission. The output gears of the diff drive the axle shafts through heavy splines.
If that one shrink-fit coupler were to be loose enough to cause what I'm hearing, it would make a ton of noise, and would have filled the pumpkin with metal. Neither happened.
LLoyd
Reply to
Lloyd E. Sponenburgh
"Denis G." fired this volley in news:054f7966- snipped-for-privacy@6g2000vbv.googlegroups.com:
It's not a PDS cart, so it has no speed sensor.
This controller is a "dumb" PWM type, without regenerative braking or automatic speed controls.
LLoyd
Reply to
Lloyd E. Sponenburgh
Can you put a volt meter somewhere on the motor leads, or measure the battery current or voltage drop under load?
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Mine is a cheap plastic model with a +/-75A scale for the alternator and a +/-400A scale for the starter.
For those who don't know, non-contact current meters work only on single cables carrying current in one direction, not pairs with both power and return such as from the controller to the motor. That applies to AC clamp-on meters too.
jsw
Reply to
Jim Wilkins
"Jim Wilkins" fired this volley in news:jseuc7$t66 $ snipped-for-privacy@dont-email.me:
It's a PWM controller, Jim. My DVM does a pretty bad job of showing the average voltage of a square wave.
Nonetheless, I was able to determine that the motor was not actually rapidly spinning; it was creeping at about 100rpm, but "singing" or "ringing" at the PWM switch frequency -- just without any real power or speed (full throttle). I checked the brushes, and they're like new.
Likely it's a controller issue. I have a spare PDS controller, but will have to spoof a speed pickup signal to make it work. There are no provisions on my motor for the PDS speed pickup.
Another hour or so of digging ought to get to the problem. I have a 'scope, but can't bring the cart indoors, and I'm not taking my scope out in the misty drizzle that's blowing into the shed right now (aftermath of TS Debby). Maybe when the sun comes out this afternoon.
LLoyd
Reply to
Lloyd E. Sponenburgh
(...)
'Sounds like the controller is current - limiting; narrowing it's PWM pulses because it thinks the motor is shorted.
--Winston
Reply to
Winston
I know. It's easier when you have another known-good machine in the shop to compare the reading to. Flat-out acceleration should briefly show full DC voltage, though.
jsw
Reply to
Jim Wilkins
So no circuit feedback.
Oh well, it always pays to check the simple things first. Maybe the board won't be too complicated if you have to figure it from scratch. I understand the basics of PWM, but don't have practical experience. I would now guess a bad SCR or the oscillator circuit went kerflooey, but I'm mostly a hex head.
Reply to
Denis G.
"Denis G." fired this volley in news:8b707822- snipped-for-privacy@v15g2000yqi.googlegroups.com:
The couple of cart controllers I've taken apart (after scrapping) didn't use GTO SCRs, they used really husky MOSFET drivers. I think GTOs are still extremely expensive compared to large, paralleled SmartFETs.
Back in the mid-80s, before carts generally had PWM controllers, my dad and I designed one from scratch, using bipolar transistors (at the time large enough MOSFETs weren't commonly available). It ran the motor fine, but we could never find big enough flyback diodes to protect the transistors from inductive kickback, and slow switching would overheat everything. We faced other impediments, like not having the right motors for that sort of control.
The first commercial ones were about the size of a LARGE loaf of sandwich bread, and used banks of TO-3 bipolars to do the switching.
Now they're about 4" square, with lots of IR FETs and big "pellet" style diodes mounted on TO-220 frames -- even have thermistor sensing on the heat sink!
I finally elicited from my wife that this problem "comes and goes". I think it's time to pop the cover on the controller.
LLoyd
Reply to
Lloyd E. Sponenburgh
No SCRs any more - better than 90% are MosFet units - I suspect one side of the unit, either high or low, is bad, but that's just a guess. If one side is shorted the control would go into current limit.
Reply to
clare

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