1st test drive in the car!!!!

[spiff]

So I finally did some more diag and found that my 100W 50ohm precharge resistor was blown. This was after many, many starts. I initially replaced with 100W 100ohm resistors and realized I was going the wrong way as they blew as soon as I turned the system on (again never got out of precharge).
I swapped with a 100W 30ohm resistor and it worked several times. However, when I turned the system off, and then turned it back on but just let the precharge run out while I was checking some parameters on the inverter, I went to turn it on again and it looks like the resistor died.

I haven't changed anything else since it was working fine last before the first resistor blew.

Am I using the right resistor value? Could there be anything else I'm missing? Could the parameter settings have anything to do with this?

Thanks in advance!

[arber333]

So I finally did some more diag and found that my 100W 50ohm precharge resistor was blown. This was after many, many starts. I initially replaced with 100W 100ohm resistors and realized I was going the wrong way as they blew as soon as I turned the system on (again never got out of precharge).
I swapped with a 100W 30ohm resistor and it worked several times. However, when I turned the system off, and then turned it back on but just let the precharge run out while I was checking some parameters on the inverter, I went to turn it on again and it looks like the resistor died.

I haven't changed anything else since it was working fine last before the first resistor blew.

Am I using the right resistor value? Could there be anything else I'm missing? Could the parameter settings have anything to do with this?

Thanks in advance!

There is something on the line that is always draining into precharge. Can you list your devices that consume current and go from there? Is it possible your precharge relay stuck closed? That would explain resistor death.
You need to find what component is drawing power in the 1s - 2s time precharge should happen and make that stop.

I have Eltek charger always connected on the line because it doesnt like going through precharge. But this means i need one extra 30A fuse to cover any incidents and servicing actions...

[spiff]

Thank you! The devices I have connected are:
- DC-DC converter (Tesla)
- Cabin Heater (but connected via contractor triggered by HVAC system and not on)
- LDU
- AC (Tesla, but not connected currently)
- OBC (Tesla Gen 2) - 12V disconnected for now when I’m not charging the battery to help diagnose.

I wonder if the DC-DC being connected is doing this. This is the one thing that I think has changed recently, but already in place when it last worked.
It’s turned on with 12V ignition so would definitely be on during precharge. Would that make a difference? I’m not super happy that every time I try turning it on, I blow another $5 on a resistor……

[P.S.Mangelsdorf]

I'm pretty sure this is the resistor I have. I know it was recommended by someone on the forum, but I don't recall where or whom. I would also note that this is only precharging my drive unit, the charger/dc-dc are precharged separately, which was a personal choice most don't do.

EDIT: Wrong resistor, see post below.

[spiff]

Wow. 0.5ohm 100W is 14amps peak vs 1.8amps for the one I was using (100W, 30ohm).

What is your HV battery voltage? Not sure how much of an impact the DC-DC on the same curcuit would affect things but I’ll try changing the resistor to what you’re using if it doesn’t.

[P.S.Mangelsdorf]

Wow. 0.5ohm 100W is 14amps peak vs 1.8amps for the one I was using (100W, 30ohm).

What is your HV battery voltage? Not sure how much of an impact the DC-DC on the same curcuit would affect things but I’ll try changing the resistor to what you’re using if it doesn’t.

Wait wait wait, I went back and double checked, and found the original invoice. THIS is the resistor in my car. 50 Ohm, 100W

Also my fully charged pack voltage is 398V.

[spiff]

Thanks. That would make more sense…. So next step for me is to disconnect the DC-DC and see if it helps pre-charge. Will let you all know what happens.

[spiff]

So I swapped in a 100W 40ohm resistor, but found the original params file I was using before. After I kept thinking about it, I realized that the car started blowing pre-charge resistors after I updated the parameters. So I uploaded the original params file and it started working without blowing resistors! One other question I have is that now it feels like regen is on, but it gives such a howl when regen is happening. Is this normal?? Take off, cruising and acceleration feel great!! Almost there, but I don't want to take it too far without confirming the sound is okay. Previously, when it felt like regen wasn't on, it wasn't making any significant noise when coasting or slowing down.


For the record, here are the two files for your records, (incase anyone wants them). Anyone know what the specific parameter that would have caused the pre-charge resistor to blow?
Here is the original one (with boost, fweak, fslipmin and fslipmax copied from Boxster EV's file):

params-new.json

(1.37 KiB) Downloaded 2 times

Here is Boxster EV's file that kept blowing the precharge resistor:

params-new.json

(1.37 KiB) Downloaded 2 times

As far as I could tell, these are the parameter differences between the original one ("Orig") and the Boxster EV one ("New"):

New: "sincosofs": 2048,
Orig: "syncofs": 0,

New: N/A
Orig: "minpulse": 1000,

New: "udclim": 410,
Orig: "udclim": 490,

New: "throtramp": 15,
Orig: "throtramp": 5.84,

New: "ampmin": 10,
Orig: "ampmin": 0.34,

New: "slipstart": 55,
Orig: "slipstart": 35,

New: "ifltfall": 3,
Orig: "ifltfall": 0.06,

[P.S.Mangelsdorf]

One other question I have is that now it feels like regen is on, but it gives such a howl when regen is happening. Is this normal?? Take off, cruising and acceleration feel great!! Almost there, but I don't want to take it too far without confirming the sound is okay. Previously, when it felt like regen wasn't on, it wasn't making any significant noise when coasting or slowing down.

I have a decent amount of gear noise from mine, but I've not noticed a significant change when in regen. I assume you checked the fluid level? Also check your CV joints and axles. I've had issues with mine.

Also for reference, my "street" tune is attached if you want to take a look through. This is for a Sport LDU, but I've mostly only changed fslipmax and fweak when changing between base and sport.

[spiff]

So I was continuing to do some testing (topped up the oil) and the noise was still there. So I turned off regen for now to keep testing other aspects. Slowing down is fine without it, both in coasting and braking.

But unfortunately, I almost blew another resistor. After a 5 minute spin, it was pretty warm, almost hot. It still worked, but I could tell it would fail soon.

Is there a parameter that controls letting it stay on after the main contactor closes? Is there some reason the pre-charge contact would continue to stay open?

[P.S.Mangelsdorf]

Is there some reason the pre-charge contact would continue to stay open?

Is it possible the precharge contactor is welded? Check for continuity with the car off. (be very careful. Checking contactors with a multimeter is how I damn near let the smoke out of... myself)