90 Yamaha G8 - Slow Speed (SR48500, SW202, 600A Solenoid)

DrGamete

Greetings,

Looking for help on a Yamaha G8 with top end speed issues using an SR 48500 controller.

I inherited a '90(ish) Yamaha G8. Which, I've completely rebuilt minus the rear axle. When I picked it up from my grandmother-in-law and was told it only needed new batteries. So, I put in new T105's (6/6v) and after some troubleshooting determined the controller was dead (battery acid covered the interior of the cart when I picked it up. After neutralizing everything, and a fresh coat of rust converter paint. I swapped out just about everything in the drive system except the motor. A new SR-48500, SW202, 600A Contactor, 3/0 cables between batteries, 1/0 cables to the motor and controller. While I was at it, I added a 6" lift and 25" tires. Also built a new wiring harness as the OEM one was incredibly corroded and had a ton of splices in it. I followed the Alltrax SR schematic including wire colors. Using weather pack connectors for all the connections, 36V Fuse panel and a 36-12 converter with its own fuse panel. Each voltage domain has a separate ground bus bar.

Once it was re-assembled, I took the cart for a quick spin and was disappointed, the best I can get is 7MPH, and torque was pretty low as well.

I double checked the wiring its an old style GE (terminals in a row). The motor was wired correctly, but for debugging purposes, I temporarily reversed A & S wiring just to see if I had it wrong. The cart ran same speed wired properly or with A & S leads swapped.

Thinking it may be something with the motor, I disassembled the stock motor, cleaned and trued up the commutator (though it had minimal wear). I undercut the commutator bars, installed new brushes and springs, though the brushes had about 75-80% remaining. I checked for shorts in the armature, commutator, and the field coil to the motor frame. Everything was good, I re-installed the motor. Same results, speed is limited to 7MPH.

I called Alltrax and the tech thought maybe I had a bad throttle sensor. I replaced it with a Curtis throttle sensor, today, but it also has made no difference in speed. The throttle is maybe a tad smoother, but really no different than the original Yamaha sensor.

Does anyone have any suggestions on top end speed? SR toolkit monitor shows I'm only drawing a peak of about 200A and average 57A @ 99% throttle with my foot to the floor.

I was estimating with this controller and wheel combo, I should see at least 16-18MPH on the stock motor.

Thanks for help and feedback!

Cheers,
Rob

BGW

__________________
This advertising will not be shown in this way to registered members.
Register your free account today and become a member on Buggies Gone Wild Golf Cart Forum

cgtech

Who told you to expect 16-18mph on stock motor fed 36v? They were wrong, you should expect about 12mph on stock motor. (Edit, I see larger tires). What is voltage at controller M- & B+ at full speed?

scottyb

25 " tires are 39% taller than stock so ~ 12mph + 39% = 16.68 mph mathematically ?
Assuming the stock motor can turn 25s and the battery pack, tire inflation, brake resistance, etc. is all optimal.
I guess that is how the got the advice. Certainly 48v would be better.

cgtech

Yeah, I have edited that to reflect larger tires. I sort of feel the stock motor will be pretty hopeless against 25" tires.

scottyb

I agree - I wouldn't suggest it - especially on 36v

Merry Christmas

DrGamete

16-18MPH was from my math using the same estimate as you guys. A percent over from stock speed with larger tires. Originally, years ago I estimated it ran 12-14MPH, so jump the tire size increases the speed to about 16-18, which requires more current. So the higher amperage controller should allow me to maintain stock axles turn rate and larger tires equaled the expected speed.

Yes jumping voltage will also increase speed, but that will increase axle rotation rate not rolling speed.

Unfortunately the motor isn't drawing much for current 50a @ 37.6v @ 99.7% throttle according to alltrax toolkit.

I've think I'm down to a bad controller or bad motor. Just changed the throttle pot out to a Curtis, I had one questionable spit in the stock original pot.

Any ideas?

Sent from my SM-N950U using Tapatalk

DrGamete

Just measured across A1 & A2 - Im only getting 15.6v across the two terminals contrary to the alltrax software info.

Bad controller?

Sent from my SM-N950U using Tapatalk

DrGamete

Took measurements at all the voltage points for reference:
(All measurements @ full throttle unless stated otherwise)

The cart was stationary on jack strands and the motor was not allowed to over speed, just ran long enough to stabilize measurement on DMM.

Battery Pack (6/6v) = 38.7v
B- to controller side of solenoid (actuated) = 38.7v
Controller+ to Controller- = 38.7v
B+ to M- = 16.8v (Same as A1 to A2)
F1 to B- = 16.3v
F2 to B- = 16.6v
F1 to F2 = 0.3v

cgtech

Well, it's clear to me that the controller's output is only half. For whatever reason. Can you connect to it with a laptop?

We need to see if the controller thinks it's always in reverse. This can be checked on monitor page, or disabled on the "1/2 speed reverse" check box on the first page.

DrGamete

cgtech,

Thanks for your help. I checked this at least twice with the Alltrax tech support and thought I'd reviewed it a few times myself. You are correct I'm in half speed. I apparently have reverse tied to the center post of my SPDT F/R switch. I know I tested this with the Alltrax tech, but I'm not sure how I caught this earlier.

I'm now at 13MPH average with a few spots hitting 14MPH on a long straight. Still not what I was expecting, but its at least respectable without a motor upgrade or tuning the controller yet.

I pulled the Rev input, and will run that way for now. I'll cut the wire harness apart and run the Rev cable directly to the Rev solenoid.

Cheers,
Rob