Alltrax going bad???

[gsf35099]

Hi gang,
Anyone seen an Alltrax controller have intermittent problems that stops the cart and after some time sitting idle begins to work again?

Details:
Alltrax 500A made in 2004, 400A solenoid, 2 gage wiring, 48v (6 -8's)

My batteries were 7 years old and the first time the problem happened I heard a small pop and the cart died. Voltage gage on dash read 50.7 volts (had been on the road for a while) and every time I stepped on throttle the volts would drop to ~33 volts & no movement.
Measured the batteries and had a center battery only reading 6.9 volts.
Replaced all bats with same Trojans 875 and cart began running like it should. Only drove it a short time maybe 15 min & parked to move on to other projects thinking problem was fixed.

Drove cart today a few times with no problems, then last time I heard that same pop and cart stopped & volts drop from 52v to 33v. Every time I step on throttle the volts drop hard. I measured all bats and they are 8.8-8.9v. Everything is clean and tight, so I figured the controller must have died causing the voltage drop.
After the cart sat for ~4 hours, it's working fine again.
I'm thinking the controller is flaking out on me and looking for some confirmation before I drop money to replace it. or at least some inputs of maybe how to further check that it is the controller when it happens again.

Thanks

[scottyb]

I think you do have a controller problem but I'm not sure exactly what goes pop and still allows the cart to move, usually the pop noise is followed by no movement. You may want to call Alltrax tech support and ask Will or Ron what they think is going on.

[gsf35099]

Thanks scottyb.

I also thought the same thing & the first time thought it was that low battery that maybe lost a cell. Then yesterday the pop. It's not real loud and I could have sworn I could smell an electrical burning smell, but real faint. Thought for sure controller died.

[scottyb]

Check all the batteries too.
Check individual voltage at a stand-still and again under load (while accelerating)

[gsf35099]

I did check them at stand still and they all in the upper 8's. Didn't check them under load, but pretty sure they are okay since the cart is working again and here's why.

Watching voltage meter on dash for pack - When cart is working like now, I accelerate (solenoid engages) and volts stay in the 50's while moving slow or just keeping a slight load on them. Will test top end here shortly, but normally runs ~25mph with a fresh charge.

When having issue like yesterday, as soon as the solenoid clicked, the volts would drop as I pushed on accelerator into the 30's with zero movement like there was a huge drain on them not going to the motor. As soon as I let off accelerator, the volts snapped back to 51+ volts.

Weird problem. Normally solid state electronics die & don't work again, but maybe something like a resistor/scr/cap in the controller is getting hot and malfunctioning until it cools down. Still a strange one.

[dundeebarnbuggy]

Taking a shot in the dark here. Are you sure it is not the motor that is sucking up all the amps? I'd clamp your meter on one of the motor cables and check. I've had a couple of bigger, [5hp] AC brush motors do that here in the past. One was an easy fix, the brushes had come out of "time" and the other got it's retirement.

[gsf35099]

Thanks, that's a good idea to measure the volts coming out of the controller to the motor when it's having a problem.
Would the motor be intermittent though? Would think that if something went wrong it would stay wrong and not recover from sitting.

[dundeebarnbuggy]

From my experience for this problem, volts can give a clue but amps can give a better one. I have had motors/an alternator and numerous coils that work fine cold but fail/short when hot. Assumed it had to do with the insulation softening/melting in the fields or coils. I'm sure someone here with more experience working inside these motors can confirm or deny.