Trying to get to Spin City...

Topics concerning the Tesla front and rear drive unit drop-in board
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espriev
Posts: 44
Joined: Mon Jan 02, 2023 5:32 pm

Trying to get to Spin City...

Post by espriev »

Rear SDU test bed so far:
I have plotted the pot 1 values (822 to 4395) from my Subaru e-pedal and entered the values, rebooted & refreshed and it reads the same.
I have four 12 volt 100 ah batteries in series for 48 volts feeding the contactors, and a 650 watt 120 volt light-bulb in series with the - side (that was convenient, I don't see how it would matter which side it is on?). I have UDCSW set to 38 and UDCMIN set to 0.
When I turn on +12 (ign) the pre-charge contactor engages, when I press START the main contactor engages (getting about 50VDC at the inverter).
I put it in forward or reverse, then press on the pedal even a small bit and the bulb lights up bright, no motor rotation at all. Traction voltage goes down to 1 volt. It stays this way until I put it in neutral. Back in neutral the light=bulb goes out and the voltage goes back to 50.
Motor does not spin in any pedal position.
I read 43 kohms across the inverter / motor DC connectors (batteries not connected).
All wiring has been triple checked, correct voltages from all switches at the 20 pin connector.
For the test set-up I am using a set of battery jumper cables cut in 1/2 to connect the traction battery to the contactors / light-bulb, and the other 1/2 to the inverter / motor. Might this be too weak of a connection (jumper cable clamps)? They are not heating up at all.
Any thought / ideas?

Thanks!

Update:
I replaced the jumper cable clamps with copper lugs, no change. So a weak connection was not the issue.
My next thought it to parallel a 200 amp fuse I have with the light-bulb, my thinking is if the fuse goes the bulb could provide back-up protection.
Am I correct that if an IGBT was shorted I would see that at across inverter traction battery connections, and if one (or more) were open I would get less current draw (the bulb lighting up bright and the B voltage going way down indicates high current draw to me)?

Update #2:
So I went ahead and connected the 200 amp fuse in parallel with the light-bulb and it spins in both directions!
No cruise control or brake switch action, but I am optimistic these features are not enabled in the default set-up and simply need to be enabled.
So of note to those who do not have convenient access to heater element wire for their test set up, the light-bulb suggestion has issues. Possibly a much higher wattage bulb may work. I can not state with confidence that the light-bulb in parallel with the fuse provides adequate protection, but it is certainly better than just a fuse.
The time, work, and investment it has taken to determine that the SDU I purchased actually works has brought huge relief!
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