Tesla LDU Controller Stops Working with Aggressive Throttle

[eGrandpa]

My conversion is up and running. I'm using the equivalent of a Tesla Model S Sport motor with a 96s72p LI 400v battery (essentially the same as a Tesla S 85). I have tuned the throttle and reg. They seem fine and were close already. However, I can get the main HV contactor to turn off with an very aggressive throttle tip-in from launch up to really any speed. I have to stop and turn off / on the system to start again. Regular driving is fine even with some aggressive throttle input. The actual current draw doesn't seem to be the problem. I don't get any error messages. It's not the BMS as the issue is tripping the main contactor, not the BMS controlled relays. Any thoughts on why?

[P.S.Mangelsdorf]

Two thoughts:

1) Make sure that you have tripmode set correctly, it shouldn't be opening the contactors, it should just be putting the inverter to STOP. This will still require a power cycle to restart.

2) This is a known issue that we're working on a solution to. I believe I have sorted out the issue, but will be testing further this weekend. See: viewtopic.php?t=3774

Can you share your parameter file?

[eGrandpa]

That's exactly what mine is doing as well. Sorry I didn't see your post. I'm only into the test mode for a few days. Other than this issue, the controller seems to work fine. I converted a 2008 Corvette so there's considerable expectations / pressure to achieve an appropriate acceleration rate . I will attempt to share my parameter file if I can figure out how to do it. I will be following your progress with great expectations!!

[eGrandpa]

Here is my parameter file --

params.json

(1.25 KiB) Downloaded 52 times

[P.S.Mangelsdorf]

That's exactly what mine is doing as well. Sorry I didn't see your post. I'm only into the test mode for a few days. Other than this issue, the controller seems to work fine. I converted a 2008 Corvette so there's considerable expectations / pressure to achieve an appropriate acceleration rate . I will attempt to share my parameter file if I can figure out how to do it. I will be following your progress with great expectations!!

It's good to know that others are having the issue. I believe you're the 3rd confirmed car where its showing up. It's interesting that you have a sport unit, that answers one of my questions about whether its truly a hardware limit.

Looking at your parameters, you have ocurlim fairly low. Try raising that above 2000 (mines at 3500), and see if it persists. To the best of my knowledge the sport LDU is known to safely pull 1200+ amps. I think in your case, you might just be hitting ocurlim. If you are still hitting the shutdown with ocurlim at 2000+, then we know its some other part of the firmware or parameters.

[eGrandpa]

Put ocurlim to 2000. That seems to have been the issue. Works great. I will test some more. Thanks for the help!!

[catphish]

You have got tripmode set to 0 (AllOff)
Set this to 1 (Keep DC switch closed) immediately or you WILL destroy your inverter.

Next, the fact that this is happening means you are likely exceeding your current limit. You need to actually consider what current you are comfortable with, and either increase the limit, or tune the system not to exceed it.

[P.S.Mangelsdorf]

Put ocurlim to 2000. That seems to have been the issue. Works great. I will test some more. Thanks for the help!!

Great!

It's good to know that those settings seem to work on the sport LDU; it gives credence to the idea that we're just pushing the base units a little to hard. (and makes me optimistic about the sport unit sitting in my garage waiting for testing)

[eGrandpa]

Is there a correlation between ocurlim and actual current amount? Also, what do I have to do to detune. Looking for of course a good balance. I did change the trip setting to 1 after you mentioned it. thx

[catphish]

Is there a correlation between ocurlim and actual current amount? Also, what do I have to do to detune. Looking for of course a good balance. I did change the trip setting to 1 after you mentioned it. thx

ocurlim is the peak current that is allowed to flow through the inverter and motor. If this is exceeded even for a fraction of a second the inverter will shut down. It is a safety feature like a fuse (but much faster than a fuse). I don't know what a good limit is for the LDU as I don't have one, hopefully somebody else can answer this. Once the limit is set, if you are hitting it and the inverter is stopping this is harmless (with tripmode=1) but it means you need to reduce the tune a bit.

As a simple rule, if you hit the limit when going full throttle at 0mph then you should reduce the value of "boost". Boost is how much current it pushes though the motor at full throttle from a standing start. If it's too high, you'll be pushing too much current at very low speeds.

If you hit the limit going full throttle at higher speeds then the solution is to increase the value of fweak. Fweak is the speed (in Hz) at which full battery voltage is applied to the motor. If this is too low, you will be pushing too much current at medium speeds.

It is almost impossible to push too much current at higher speeds (>60mph).

[muehlpower]

ocurlim is the peak current that is allowed to flow through the inverter and motor. If this is exceeded even for a fraction of a second the inverter will shut down. It is a safety feature like a fuse (but much faster than a fuse). I don't know what a good limit is for the LDU as I don't have one, hopefully somebody else can answer this. Once the limit is set, if you are hitting it and the inverter is stopping this is harmless (with tripmode=1) but it means you need to reduce the tune a bit.

As a simple rule, if you hit the limit when going full throttle at 0mph then you should reduce the value of "boost". Boost is how much current it pushes though the motor at full throttle from a standing start. If it's too high, you'll be pushing too much current at very low speeds.

If you hit the limit going full throttle at higher speeds then the solution is to increase the value of fweak. Fweak is the speed (in Hz) at which full battery voltage is applied to the motor. If this is too low, you will be pushing too much current at medium speeds.

It is almost impossible to push too much current at higher speeds (>60mph).

"Fweak" also concerns me. Shouldn't it be lower with an empty battery than with a full one? So be dependent on the current battery voltage?

[catphish]

"Fweak" also concerns me. Shouldn't it be lower with an empty battery than with a full one? So be dependent on the current battery voltage?

It's not terribly important, but if you want that, openinverter will do it automatically, just set udcnom to your nominal battery voltage before you start tuning.

[eGrandpa]

If someone knows the recommended ocurlim for the Tesla Sport LDU that would be great. My worst fear is setting it too high and causing the inverter to sink too much current before ocurlim trips.

[Boxster EV]

I’ve always left the value of my Base unit at -2500.

However, when bench testing I used a value of -300 and gradually increased it until I was comfortable that there were no underlying issues.

[mane2]

I seem to have it -2500 too with my Sport unit. Have got overcurrent error few times, but only once when accelerating. And that time, the rear suspension started to bounce (wrong damper settings) so I think it caused a current spike and tripped overcurrent.

3-4 times I have had weird shutdowns (probably overcurrent too) when reversing off my yard, and switching direction .. I haven't figured out what causes that yet. As it's 1-way road and been busy getting the car to start again, not blocking the road.

btw, would be nice to have bit more permanent error memory. I think current one gets erased on when motor loses 12v power.

[eGrandpa]

It seems that ocurlim value is the same as the current in amps. So, 1000 ocurlim = max 1,000 amps. I set my ocurlim to 1500. I made my own battery using Tesla 18650 cells in a 96s72p configuration made with double Battery Hookup fusible links at the cathode. Given that, I didn't want to exceed the fusible link capabilities. I lowered boost to detune from 2500 to 1700. These two changes seem to make a big difference. I haven't exceeded my current limitations with some still pretty aggressive accelerations. Nice balance. I haven't yet tested full throttle at 0 mph, but I never drive that way anyway. Lowering boost also seems to have increased my range as well. I may tweak in the future, but I sense that I'm close now. Thanks again for everyones input.

[Troubled81]

I have a P90+ and it dynos 515hp to the wheels. I have logs of it pulling close to 1300amps and 300volt (it has one of the new 350v 90kWh batteries aka 7/8th a p100d pack). I am pretty sure that it will tolerate 1400+ amps but need to get around the rate of change limit the stock tesla board is locking me down with.