Issues with precharge, precharge lets go after 5 sec

[Permag]

Greetings. Yesterday we had the car at the track. We unloaded the car, tooled around about 500 feet at low speed. Rolled into the throttle then DEAD. After, precharge would come on for 5 seconds then it lets go. Udcsw was set properly, but I have moved it down to 300 volts. Precharge occurs and brings motor voltage to 365 ~ 2 volts from pack voltage. Then it shuts off with a precharge code of 501. Damien has helped me eliminate a few thing
Any suggestions?
-Thanks

[arber333]

Greetings. Yesterday we had the car at the track. We unloaded the car, tooled around about 500 feet at low speed. Rolled into the throttle then DEAD. After, precharge would come on for 5 seconds then it lets go. Udcsw was set properly, but I have moved it down to 300 volts. Precharge occurs and brings motor voltage to 365 ~ 2 volts from pack voltage. Then it shuts off with a precharge code of 501. Damien has helped me eliminate a few thing
Any suggestions?
-Thanks

This feature is in code because of me . It is a failsafe that prevents you from starting the car into precharge or burning your precharge resistor or even your main fuse because of some DC switch problem. Your precharge should be able to raise voltage in some 3s. 2 remaining seconds are there just because...

Try inspecting the ULN2003 chip for burned transistors or abnormal behaviour.
I never use ULN2003 chip to switch DC contactor directly. I allways use another small relay. Preferably 2 12V arduino relais, one for precharge and one for contactor. That prevents high loading on ULN2003 chip. Also Johannes reported some strange behaviour of reverse diode on that chip, so i just clipp that leg off the chip before i install it. That diode is supposed to absorb back EMF from large relay coil discharge. But i use a small relay instead and never had a problem since.

[Permag]

Well as it turns out, the negative regulator just above the 8 pin connector was bad, not allowing the board to see voltage at all, If it were a bit cooler, quieter at the track we may have figured it out before leaving. We couldn't even see our screens at the track it was so bright.