Tow/Run switch and solenoid

[Ezgo - N]

As I a buddy and I finished installing an Alltrax XCT500 controller onto my 04 Ezgo, the positive battery cable arched when I went to attach it back. This has caused the regen diode to blow. I had the cart in tow mode but had left the key on My question is this. While in the tow position does power still go to the solenoid with the key on or is there a chance I have wired something incorrectly? After spending a good chunk of change on a new controller, I certainly don't want to fry it.

[Andy4639]

There shouldn't be any power on a 04 PDS cart in tow.

[Ezgo - N]

That was my understanding as well but there was was enough current going to the diode at the solenoid to melt the wire down.

[JohnnieB]

Since the filter capacitors in the controller were completely discharged, if the regen diode was installed backwards, you'd most definitely get an significant arc when the last battery cable was connected.

Which wire was melted down? The diode lead?

[Ezgo - N]

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[Ezgo - N]

JohnnieB to clarify the situation, I did charge up the controller before I realized that I failed to put on the diodes. Also, I'm not sure if it makes a difference but I put my 400 amp ann fuse on my negative lead

[JohnnieB]

Originally Posted by Ezgo - N

JohnnieB to clarify the situation, I did charge up the controller before I realized that I failed to put on the diodes. Also, I'm not sure if it makes a difference but I put my 400 amp ann fuse on my negative lead

If the Run/Tow switch had been it Tow, or the battery pack disconnected for more than about 5 minutes or so, the filter capacitors would have been discharged, or close to it. For safety reasons they have a bleed network that discharges over a few minutes so an unsuspecting person won't get zapped if they touch the wrong places on a disconnected controller.

On the XCT, the capacitors are normally charged via J1 Pin-5 and inside the controller there is a resistor in series between Pin-5 and the capacitors, so the peak inrush of amps is held down to an amount that is within the specs of the Run/Tow switch contacts.

If the regen diode was connected with the banded end connected to the solenoid's controller side large terminal, the unrestricted inrush of amps would have been in the hundreds if not thousands for the microseconds or milliseconds it took to vaporize the ring connector.

As for the fuse, anywhere within the battery pack or on either end is fine. When I was running a DCX controller, the fuse was on the controller end of the B- cable.

[Ezgo - N]

JohnnieB I appreciate the information! I'm in the process of making up another diode now and I'm going to give it another go.
Would there have been any concern from damaging the controller when the diode melted down or did it sacrifice before this was able to happen?

[JohnnieB]

Originally Posted by Ezgo - N

JohnnieB I appreciate the information! I'm in the process of making up another diode now and I'm going to give it another go.
Would there have been any concern from damaging the controller when the diode melted down or did it sacrifice before this was able to happen?

Probably not. The capacitors are connected between the B- and the B+ buss bars which are designed to carry at least 500A in an XCT48500-PDS, but it would be best to check with Alltrax.

Be sure to have the banded end of the new diode connected to the solenoid's battery side large terminal.

FWIW: The purpose of the regen diode is protect the controller if the solenoid contacts open while regen braking is occurring. During regen braking the motor acts as a generator and the resulting electrical energy is fed back into the battery pack. When the solenoid contacts are closed, the battery pack keeps the voltage down to whatever the pack voltage is at the time, but if the contacts open, the voltage output from the motor (generator) skyrockets and the controller can get hit with a lot more than the 62V it is designed to tolerate. The diode keeps the motor's generated output connected to the battery pack in case the solenoid contacts open.

Turning the key off while slowing down will open the solenoid contacts during regen braking and so will certain wires breaking, but for the most part, it is a rare event.