Tricky Elec. Issue - Need to pick your brains

[stang99x]

I install a digital LED voltmeter in all my cart builds. The factory led bar design is crap and half the time is wrong anyway. You can run a piece of speaker wire from the main positive and negative posts to the glove box for a temporary setup. The little gauges I buy from China and they cost about $3 each. They are water resistant, good to 100V and I've found them accurate to within .1 volts in 99% of units. I don't leave them installed as an "always on" type unit for customers, I put them into the ignition so they only come on with ignition on. But for you always on will work to diagnose. I would imagine that you will see a severe drop when it won't go or barely moves. As I sat and thought more about it, it could be so many things it's really hard to guess, but I have seen a motor that had worn out brushes act in a similar manner. But that cart saw daily usage for many, many years straight

[konakid]

Thanks again for your time and advice.

I hooked up the digital meter. to view when driving. And with the cart not fully charged it read 38v at rest. While going uphill full speed it dropped to 32.5v. So I guess that means the batteries are decent???

So, I am now set up to see what it reads during the next episode. Hopefully it will be something telling. I'll post again when something happens.

[stang99x]

A drop while accelerating is normal. I see up to 8 volt drops at full instant throttle on 48v carts. I think my 36v txt series drops to about 32-33 under full load from a dead stop, though I do have aftermarket controller and motor installed. That voltage should return to closer to pack voltage once you have achieved full speed

[konakid]

Well - don't know if this is good news or not.

After a full charge and a few spins around the property, it ran well with voltage dropping to 33-34v up the steepest hill - but went right up nicely, no effort.

Then - when going up the same steepest hill for a third time, and with the voltage dropping to the same 33-34v, it slowed and stopped. I tried again, and it just barley made it up - again with no drop in the voltage under 33v.

I spun around the loop and went up the hill for a fourth time. No problem at all - voltage the same, 33-34v - and it went right up.

I hope someone has a suggestion as to what to do now. Please.

Can I take the leads I have hooked up to the battery pack and meter and instead hook them up to the terminals at the motor? From the little that I know, if I have full voltage at those terminals, and it slows and stops (or if it refuses to move, even on flat ground), then wouldn't it have to be a motor problem - which I definitely don't want, do I?

Edit: I went ahead and did it - the results are as follows.

[konakid]

I hope a few of you guys are still reading this, if only for curiosity - because perhaps I have some more clues to help diagnose. Below are pics of my motor and controller.

I am getting four blinks and a solid green when turning key and flipping dash mounted F&R. However, sometimes I hear the solenoid click at the first blink, sometimes the third blink, and then occasionally not at all - but cart will still run. I have no idea what any of that means.

I hooked my meter up to the two fat wires on the motor terminals. And I'm getting the following results:
- when pedal to the metal it goes up to 30+
- when coasting very fast downhill, it goes up to 30+ (is that regenerating braking?)
- but when going up a steep hill it seems to hesitate intermittently with the voltage dropping under 20v
- and as a reminder, when I had it hooked up directly to the battery pack, the readings were much higher, and within an acceptable range from what I know.

I was just playing around before dark, so I don't have full readings yet when the cart stops altogether.

But I thought I would see if anyone has anything to offer until tomorrow, when I may have more info. I guess my biggest questions are - do any of these readings mean anything to anybody? And/or will any more readings from the motor terminals help figure things out?

[kgsc]

You may have a solenoid that is failing and making bad contacts inside. I didn't see it in the picture but did you replace it when you put the Alltrax in ? Also if it is failing the precharge resistor on the solenoid main post will get very hot.. You can also give it a good whack with a screwdriver handle to "adjust" it and try again.

[stang99x]

Under 20v is a problem. Not enough voltage to even run, the safety shutoff comes into play at, I think 26v? The alltrax should give you a code with blinking lights.....somehow I missed that you had an alltrax in the beginning. However you have eliminated a few areas and now know that the issue is in voltage from the controller to the motor (assuming that low reading at the motor was with normal voltage on the pack). I'll read further later as I'm on my phone at the moment.

[jjance]

I agree with kgsc. I think your solenoid is bad.

[stang99x]

I should have said between the solenoid output and motor.

[jjance]

when I had it hooked up directly to the battery pack, the readings were much higher,

When you are measuring at the battery pack you are measuring the no load voltage. When you are measuring at the motor terminals you are also measuring the voltage drop across the cables and connections including the solenoid. The difference in the two readings is what is being lost in those connections. My guess is still the solenoid. Next time this happens feel the precharge resistor and see if it is warm.