What causes greater than 5v diff across solenoid?

[tsmith_co]

So I’m my random issue I’m trying to understand how power is supplied.
(2000 ezgo series motor)

Batt + goes into the right larger terminal.
Left to B+ on controller.
Resistor between the 2

Small terminals on solenoid:
Right: red on Alltrax as well as red to peddle.
Left: black in alltrax
Diode between them with stripe on right side.

This is all setup correct. However, on 2 occasions now, my cart randomly hasn’t gotten solenoid clicks (tried 2 diff solenoids). The reason is, the left large terminals has too low voltage. (Sometime 10-14v difference).

After the cart has sat overnight, the problem usually has gone away.

So, the big question: what is actual long providing the voltage onto the left (controller side) large terminal on the solenoid?

The click is the actual connection of left and right terminals, thus passing the voltage from the right on through to left, correct?

So, is the resistor allowing to voltage over (to pre-charge the controller) or is the voltage coming in from the smaller terminals on internal workings in the solenoid? (I’m actually not sure how the little terminals work).

Thanks

[JohnnieB]

Which model of Alltrax controller is installed?
There have been several for series drives over the years. (AXE, SPM, SR, etc.)

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There is no direct electrical connection between the small terminals (Solenoid coil) and the large terminals (Solenoid contacts). Technically, the two circuits are in parallel across the battery pack, but one passes low amps to energize the solenoid and the other passes high amps through the solenoid contacts to the motor via the controller.

The voltage drop across the pre-charge resistor between the large terminals is determined by the amp flow through it and if you know the Ohmic value of the resistor and the voltage applied, you can calculate the amp flow ( V / R = A ). Normally the amp flow is determined by the bleeder network on the filter capacitors in the controller, so a jump in the voltage drop means something inside the controller is drawing more amps.

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When the cart won't run, is the LED on the controller flashing an error code?

[tsmith_co]

Thanks JohnnyB.

It’s the sr48500. 400amp solenoid.
Resistor is 470ohm.

The error when it happens on the controller is 1green,6 red - precharge failure. (More than 5v difference).

It’s not doing it now (of course!). Measuring voltages, I get full voltage across the resistor when it’s not connected to the controller side of the solenoid. When connected, the controller side of the solenoid is around 5v less than battery. When the problem occurs, I’m 10-14v less.

The resistor is measuring 460ish ohm - I’m assuming that’s close enough to the 470 rating?

[JohnnieB]

So the voltage when measured from one of the solenoid's large terminals to the other large terminal is normally 5V and is 10V to 14V when it is misbehaving?

When there is a 5V drop across a 460Ω resistor, there should be about 11 milliamps flowing through the resistor and the flow is about 22ma for 10V and about 30ma for 14V.

Where the additional 10 to 20 milliamps of current flow is going isn't apparent and it being intermittent makes it more of a mystery.

Cleaning all the connections might eliminate the problem or connecting the black wire from the solenoid coil to B- instead to the controller might work.

Give Alltrax a call, maybe they have heard of this problem before.

[tsmith_co]

Update: I’m pretty sure it’s 2 issues. My solenoid hasn’t been clicking lately and I think it’s the pedal, as when I do get a click, I get a surge of power, and not a small accel like normal.