Club car Precedent left charging in the rain - now won’t move

[Jimmer76]

Hello,
I’m new to golf carts and had a massive brain fart.. I left my cart charging at my camper with no cover and through a huge rain storm. Now the cart won’t move and the pre-charge resistor smokes..

I’ve read a lot about the resistors burning up that I’d say it is a dead controller but I want to see if the OBC is dead too or causing the issue..

Resistor measures at only 158 ohms
Resistor gets extremely hot in tow mode within a minute of connecting the battery cable. Nothing else turned on.
Measured the motor for continuity where it is supposed to and open to the case where it is supposed to be.. ( so not a shorted motor)

I noticed the charger starts once plugged in but did not click off momentarily and restart like it usually does. This is why I fear the OBC is dead too, it I stopped looking into this since the controller seems shot.

Any ideas on how to confirm either it’s just the controller or if the OBC is done too. Or maybe there is something else I am missing

I took everything apart today and even the controller opened up but it didn’t have any signs of water in it and didn’t smell burned up..

I couldn’t smell anything bad on the OBC either.. just the resistor smells because of the melter lead covers..

Solenoid was clicking when I turned the cart on and pressed the go pedal.

Thoughts?

Thanks
James

[sthreatt]

Sounds like it has all the markings of a genuine nightmare, but if you can switch it on, hit the pedal and engage the solenoid, I wouldn't be too quick to write off the controller. I'd have to do some more digging before I jumped off that cliff. You could be right ... might just be my stubborn overly optimistic nature pulling at me.

[Fairtax4me]

Sounds like the controller bit it. The only two things that make the resistor smoke are a shorted motor, or a damaged controller.

Would have to be one hell of a rain storm to get something wet enough to damage the controller, but it could also just be coincidence.
Maybe it got struck by lightning?

[Jimmer76]

There was apparently a massive thunderstorm with lightning all around. The 120v outlet the charger was plugged into had tripped the gfci as well.

Next question is what controller to replace with. Navitas or Alltrax? Did I read the Alltrax has some sort or short cct protection?

I was geared up for a Navitas upgrade based on what I had seen on YouTube. But now I’m unsure.

[Jimmer76]

Honestly I can’t get past the change in operation of the charger and the fact that the resistor measured at 158 ohms. Isn’t this supposed to be a 470ohm resistor? At 150 it was running at around 15w so no wonder it melts things. If it were actually a 470ohm then it would be 4.5w ish.

Can a faulty OBC lock out the controller from operating? I read that it shuts down the controller when charging. That said can it shut down the controller but in a way where it’s calling for power?

And lastly, if these controller ps fail such that they roast the resistors because they are “on” why doesn’t the motor run when the go pedal is pressed?

I should have also mentioned there seemed to be some low speed surging and maybe a dead spot with light pedal activation. Not sure if that is a sign of something coming.

[Fairtax4me]

A bad OBC can lock out the controller.

How you describe the OBC working is normal. If you do a full charge, unplug the OBC and plug it back in without moving the cart, it will start an equalization charge cycle which it does not need to monitor the pack change, so it will not do the shut-off after the initial start.
The OBC does not pull power from the solenoid. So it is never the cause of the resistor cooking.

Resistor measuring 150 ohms is probably because it has already cooked itself.

The damage that happens in the controller is usually one of the field driver FETs gets shorted, and then it continues to draw power regardless of whether the cart is on or off. Since the controller pulls power through the solenoid, and the solenoid is Open, all of the current is being pulled through the resistor instead, which is what makes it cook.
With the field driver damaged it has no control of the motor field current, so it can't tell the motor to move.

If there was a thunderstorm then its possible it got hit by lightning or a power surge of some kind. In that case I would probably expect the OBC to not work at all, but since it still commands the charger on, seems like its still working to me.
The only way you're going to find that out if its really damaged is to be able to run the cart and run the batteries down so you can do a full charge cycle, and see if the charger behaves normally.

You can check the OBC interlock control to see if it is sending voltage to the controller. Unplug the charge cord, find the 6 pin connector from the OBC, back probe the Blue or Light Blue wire and see if there is 48V present. If so, the OBC is giving the controller command to operate.
If there is No voltage present on the blue wire, then jumper the White wire to the Blue wire, this will provide 48v input to the controller to disable the charge interlock.

[Jimmer76]

Thanks. I’ll give this a try. I have a 20w 400 ohm resister to put across the solenoid so that it doesn’t burn up. Any reason this wouldn’t work for normal operation instead of a 470?

With this on I was then hoping to see if it would take a charge. The batteries are down to 50.5v so they may take some charge as they sit. It was sitting there frying that resister for a few days draining the batteries ever so slightly.

[Fairtax4me]

It will take longer, but it will still get hot.
The resistor only provides current to the capacitors in the controller prior to the solenoid closing. When the caps are fully charged there is no more power draw, and then the resistors job is done.
The problem you have right now is there is a short in the controller pulling power all the time, and it’s pulling more power than the resistor is designed to handle. The controller is still damaged, replacing the resistor will not fix that, even though it will need to be replaced after the controller is repaired/replaced.

The only other possibility is a short in the motor, which can be determined by disconnecting the cables to the motor taping off the ends so they can’t touch anything, then reconnecting the battery pack to see if the resistor still heats up with all of the motor cables removed. If it still gets hot, the controller is the problem.

Charging has nothing to do with the resistor. But if the resistor is cooking it will continue to draw the pack down. To get a full recharge simply disconnect the pack negative, then remove the resistor from the solenoid, make sure the pink or red wire and the pack positive cable on the solenoid stay connected.
Reconnect the pack and the charger should work and charge fine.

[Jimmer76]

Didn’t go quite as planned…. Accidentally connected the battery in run mode. Nice big arc.. then put it back into tow and reconnected, another big arc…..

I just shut it down for the night after that…

[Fairtax4me]

Did you disconnect anything? Motor cables? Resistor?

Does the cart have a voltage reducer? Those will often cause arcing when you hook up the pack.