EZGO TXT weak with New 48v batteries

[jonequest]

I have a 2004 EZGO TXT and six years ago I upgraded the controller to an Alltrax SPM72400, 8volt batteries (48volt), 2 gauge welding cable soldered (not crimped) motor F&R and controller wires, HD F&R switch, and an upgraded speed motor. It used to lurch off the line and do about 28mph which was great. Recently it had gotten real sluggish and weak so I just replaced all 6 batteries. The problem is although it is "better" it is still much weaker than it used to be with good batteries. I now suspect my batteries could have lasted me another year or so since they had clean water and were never run dry.

Symptoms are:
Take off is noticeably sluggish
Top speed is about 16-20 maybe
Torque when riding on even cut grass is very weak (It used to fly across fields of high grass)

So far I have checked and tightened all wire connections at the motor bolts, F&R switch, controller and batteries.

One issue I had recently that may matter or not is that I got a "Pre Charge Failure" error after replacing the batteries. The resistor seemed to test out at 1,000ohm (it is a 36-72v controller so that is what it came with). In any case I got errors with it so maybe it was intermittent failure. I replaced it with an old 250ohm one I had laying around and the cart was back running again. I mention this because I don't know if in some weird way the 250ohm matters. I temporarily jumped out the pre-charge resistor for troubleshooting and the cart ran that way too.

[cgtech]

I would probably pull & inspect motor brushes. A stuck brush can cause damage, and will often result in low power.

[jonequest]

Hmmm. I never though about that. I didn't think we had brushes on these motors for some reason.

[jonequest]

I think it is the brushes. I am not looking forward to pulling them out but that will be my next thing to check. I have recalibrated the controller and made sure all connections are tight and staying cold. It seems to get worse right after the first take off like the brushes are getting hot or something. I didn't expect this problem since the motor was a rebuilt "high speed" one I put in about 5 years ago.

[jonequest]

Update. I pulled apart the motor and the brushes have tons of life left in them but when I pulled the armature the brushes stayed in the same place. They are too tight to be pushed into the armature for some reason. Any suggestions?

[cgtech]

Remove and clean the brushes of any dust. Clean the brush guides thoroughly too.

[jonequest]

I was wondering if I needed to sand them with some 800 or something since they are so tight.

[jonequest]

I fixed the problem! It was the motor brushes not sliding. They were pretty much stuck in place and stayed in the same place when I pulled the armature. Two were even hard to push out. I removed them and "wet sanded" them just a tiny bit lightly with brake cleaner and 1000 grit sandpaper. I mainly sanded the inside of the brush holders that seemed to have some burrs. Then I did the same to my armature to remove the graphite buildup by spinning/wet sanding it with 1000 grit and brake cleaner as well. I put it all back together and got up to 27mph on a quick run. My top speed ever was 28mph and it takes a while to get there so I would say that is a total fix. I am sure the brushes need to settle-in a bit too. since I cleaned some tiny scars off them and the armature. I would like to blow out any build-up after the first several uses since I think that will be when they wear in and give off a good amount of dust. I am thinking of going in the little window with a long blower and skinny vacuum tube hooked to my wet vac. That sure beats pulling the whole motor again. I am attaching some photos in case they can help anyone else in the future.

[scottyb]

Excellent work
Clean and service every 5 years - who would have thought of that!?

[Dixie Chopper]

Nice work! Did you change that bearing? How hard was it to pull the shaft out of that bearing?