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Hi everyone. I’m running a Tesla model s ldu. For the precharge I am using a Zeva high voltage smart precharger. For 1000 miles of local starts and stops the controller worked well. Then it started going into a permanent error- tried a precharge but would not flip the main contactor at the end of the precharge cycle.

After checking all the wiring of my system and the resistors in the unit, I concluded that nothing had gone awry.

To try to isolate the problem I did a test where I hooked up one module (chevy volt 168vdc) instead of a complete pack and the precharge controller worked as it should. I tried the other two lower modules in the pack and they also worked but once the whole pack was connected or even two module in series (220vdc) the precharger would no longer work.

I made a temporary manual precharge switch with a 50ohm resistor and the drive unit still comes on and operates normally.

My questions are-
1. What could have changed to make it stop working correctly?
2. What would the difference be to the precharger running at 168v or less vs 200vdc or higher?

hopefully there’s and electrical engineer on here who understands the capacitor inrush properties at different voltages that could lead to a diagnosis and repair.
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