Speed issue - Tried Everything ! Seeking Advise

[sthreatt]

Originally Posted by scottyb

Just reviewed a monitor file for a similar cart using the Alltrax toolkit. The file showed where the throttle went to 100% the the motor pulled 400 amps drawing the voltage very low. Something similar could be happening here, a good pack should not drop more than a few volts at full throttle unless you are in a very steep climb.

I thought that was an excessive drop too until I saw almost exactly the same on the very healthy RXV. From the battery voltage monitor on the handheld it too dropped to and held 41 volts running full throttle on the road, and that particular cart is very fast and will run 15 miles without issue. I'm overlooking something obvious and it has me stymied.

[BobBoyce]

Originally Posted by sthreatt

I am working with a 2016 EzGo TXT48, 1 yr old batteries, will only run 10 MPH. It is in Freedom Mode 5 and will run and show 19.5 MPH on jack stands. Will only run 10 MPH on road. Have replaced with new speed sensor and magnet, no help. Replaced new/rebuilt 1206HB-5201 controller, no change. Removed motor and probed A1 to A2, S1 to S2, all checked good and no continuity to motor case from either, no continuity from A to S . Disassembled motor and looked at brushes. Blew out a lot of carbon dust, but all appears excellent. No evidence of overheating anywhere or sticking brushes in springs and guides. Put it back on, no change. I am reading 100% throttle from ITS to controller. The only fault code I am getting is LOW BATTERY VOLTAGE and after clearing, it re-appears after every test ride. Have changed and replaced with new solenoid switch, no help. Have checked all connections and cables. Pulling my hair out ! WHAT AM I OVERLOOKING ?

Controller max output is 250 Amps...

Originally Posted by sthreatt

I did consider rolling resistance. Checked tight brakes, none, bad front bearings, none, cart has a 6 inch lift and 23 inch tires, brand new and properly inflated. No resistance issues to be seen. Operating on level paved road.

Cause of increased current draw...

Originally Posted by sthreatt

Yes, I am assuming that is what the Curtis handheld is telling me, but I have monitored voltage under road driving and it shows a battery voltage drop from 51 to 41 volts at full throttle road speed. I did the same on a 2016 RXV and it also showed the same drop at full throttle on the road, but with the RXV we were actually moving about 26 MPH, so I assumed the voltage reduction was normal.

The RXV is 3 phase AC drive, is much more efficient, and requires much less current than a DC motor. I also programmed that RXV controller to not cut back or drop out at 40 volts like it would have done with stock programming. The only reason that controller drops the voltage that much is because of the performance programming. Normally, stock RXVs do not draw more than about 60% of that power under accel...

Originally Posted by scottyb

Just reviewed a monitor file for a similar cart using the Alltrax toolkit. The file showed where the throttle went to 100% the the motor pulled 400 amps drawing the voltage very low. Something similar could be happening here, a good pack should not drop more than a few volts at full throttle unless you are in a very steep climb.

Current required to drive those 23" tires to speed...


Solution... reduce tire size to 20.5" or smaller, or replace controller with a 400 or 500 Amp Alltrax controller and 2 guage high current cables. 23" tires will require a lot of current to drive to speed, and while the 1206HB-5201 is a really nice controller with lots of options, it cannot supply more than 250 Amps.

Bob

[scottyb]

I don't think you can compare AC and DC drive systems like that. What I'm saying is the drop is borderline excessive. I would look for a cause like a bad motor or a poorly set up cart, meaning tires too big, load too big, a speed motor on hills, or all of the above, etc.

[sthreatt]

I think I've been chasing a rabbit down the wrong trail. I've been focusing on voltage. I think I need to back up to square one and start tracking amperage draw.

[scottyb]

They are related. Excessive amperage draw will reduce the voltage

[BobBoyce]

Exactly!

[BobBoyce]

Originally Posted by sthreatt

I think I've been chasing a rabbit down the wrong trail. I've been focusing on voltage. I think I need to back up to square one and start tracking amperage draw.

Robert, if you want to mail me one of those 1206HB-5201 controllers, I can work my magic on it for you. It may not help much with a 23" tire cart, but it can show you what is possible with that model controller in an otherwise stock 2010+ TXT48. As for making a TXT48 with large tires perform, I suggest an Alltrax controller...

http://www.cartsunlimited.net/alltrax-xct-sepex--.html

[sthreatt]

It was batteries. I said in an earlier post that I had tried a new set with no change in performance. That was not exactly true. I was relying on the word of someone else that THEY had put in a new set and nothing changed. This had me so perplexed until I couldn't get it out of my mind. I had tried LITERALLY everything else myself, with my own hands except the battery swap. I had to see for myself because I was still thinking batteries. Put in a KNOWN GOOD TO ME set and lo and behold, it was exactly what I thought it was to begin with. Performing superbly now and will trot along faithfully @ 20 MPH. I will learn at some point to trust my instincts. Thanks for all the time and suggestions, problem SOLVED ! FINALLY !

[sigfla45]

I have the same setup and hit 20mph as well. I think its just running on the ragged edge of what the stock controller can do with 23's. My voltage sag at speed is around 45-46 volts I believe with 2yo Trojan 8v-DC batteries. Once those batteries start to lose charge you are back to square 1. It takes everything it has to get moving on 23's. I have been round and round asking Scotty questions and am finally ready to go with a 500 amp Alltrax turned down for the stock motor. I'll wait to upgrade to a high torque motor later after I upgrade to 190ah Crowns. My question however is once the 500 amp controller is able to transfer the current to the motor won't the voltage continue to suffer from a sag? Or does the increased amperage result in increased torque and efficiency in the stock motor thus lessening the sag effect?

[scottyb]

Ouch...somebody caused us all to waste a lot of resources chasing that rabbit you mentioned.
I have reviewed many Alltrax monitor files on under-performing carts and 99% of them show a significant voltage drop under load.
There are 3 common factors in all these files:
Batteries
Batteries
Batteries