"Runaway" voltage across solenoid DCS

[gwsmith1]

I went to finish up installing a SW200 solenoid on my DCS cart with a XCT48400 controller. When I went to test it the controller will not power up. No lights, no nothing. I can hook it up to my laptop and connect to it however (so hopefully no fried controller). When I check the voltage across the 2 top terminals I get runaway voltage..... .meaning that my voltmeter starts around 40 volts and just keeps counting up like I am filling up my gas tank (pack voltage is 54 volts and charging overnight). It does this with and without the regen diode as well as with the controller unplugged (meaning the white 10 pin connector removed). I am wondering if I blew a diode somehow or needed to upgrade a diode from the SW181 I did have installed or if I inadvertently yanked something loose that I am missing. I have an early morning so my troubleshooting for the evening is over, but not sure to go on this one. Any ideas or thoughts would really help until I can get back on it tomorrow evening. Thanks !

[JohnnieB]

The XCT-DCS will power up and run the cart with or without the diodes installed. they are protective devices, so they should be installed for normal operation, but okay without them for troubleshooting and testing.

What you are seeing on your voltmeter is the filter capacitors in the XCT charging. There is over half a Farad of capacitance between the XCT's B- and B+ terminals and for safety reason they have a bleeder network to discharge them so they don't stay charged forever when the XCT is disconnect from the battery. When you connect your voltmeter between the larger terminals on the solenoid, your are effectively placing a 1MΩ resistor between them and the capacitors are slowly charging through your voltmeter's input impedance.

Problem is, the filter capacitors are supposed to be kept charged to almost full battery pack voltage to reduce the amount of arcing on the solenoid contacts as they bounce to a close. I'm pretty sure Pin-10 is used to pre-charge the filter capacitors in a XCT-DCS.

Voltage source for Pin-10 is a small red wire the connects to the solenoid's battery side large terminal. That may have been left off when changing solenoid.

Also, that red wire splits inside the wiring harness and feeds the beeper as well as Pin-10. EZGO used something called a "sonic" weld that often fails and guess what, the branch that fails is the one the feeds Pin-10.


To get a XCT-DCS to power up, you need voltage on Pins 6, 9 and 10.

[gwsmith1]

Originally Posted by JohnnieB

The XCT-DCS will power up and run the cart with or without the diodes installed. they are protective devices, so they should be installed for normal operation, but okay without them for troubleshooting and testing.

What you are seeing on your voltmeter is the filter capacitors in the XCT charging. There is over half a Farad of capacitance between the XCT's B- and B+ terminals and for safety reason they have a bleeder network to discharge them so they don't stay charged forever when the XCT is disconnect from the battery. When you connect your voltmeter between the larger terminals on the solenoid, your are effectively placing a 1MΩ resistor between them and the capacitors are slowly charging through your voltmeter's input impedance.

Problem is, the filter capacitors are supposed to be kept charged to almost full battery pack voltage to reduce the amount of arcing on the solenoid contacts as they bounce to close. I'm pretty sure Pin-10 is used to pre-charge the filter capacitors in a XCT-DCS.

Voltage source for Pin-10 is a small red wire the connects to the solenoid's battery side large terminal. That may have been left off when changing solenoid.

Also, that red wire splits inside the wiring harness and feeds the beeper as well as Pin-10. EZGO used something called a "sonic" weld that often fails and guess what, the branch that fails is the one the feeds Pin-10.


To get a XCT-DCS to power up, you need voltage on Pins 6, 9 and 10.

That makes sense. I did not think about the filter capacitors. I had seem mention before that there were there but didn't understand the mechanism.... I will check the voltages this evening. Sounds like the place to start. Thanks for the help !