Losing Servo and Throttle after running for a while

[kaladeth]

[Castle 1717 1650 kV Motor, Mamba MMX8S ESC, RCP Extreme Cool 2x40x28 Fans, Promodeler DS635BLHV Servo, 19/46, stock Limitless Body, 2xSMC HCL HP 6500 mah Batteries] [Build Thread]

So this happened once during qualifying yesterday and twice today in the main race. The car would be running fine for 10+ laps, and suddenly I would lose all steering and power. If you turn off the ESC, and power up again, the car seems to be perfectly fine and keeps going. On all three occasions I think the stop was accompanied by a little bump (into the center island or on a kerb) but it might just be because I already lost control.

On all three times, the radio battery was OK (hardly used), the car batteries were still > 3.7V, and the temps when checked with a temp gun seemed to be okay. I unfortunately do not remember if the lights on the ESC were flashing any code.

Here's a plot of today's last run:

Is the "Temperature" the ESC temperature (different from Motor Temperature), and is that what's causing the seeming shutdown?

I have a pretty low Cutoff Voltage, and Motor Temperature Cutoff is disabled:

Any suggestions on what to adjust so I can avoid this in the future?

 

[Dan B.]

Going out on a limb here, but would an overheating servo cause this? I’ve experienced some heat on older Reedy and Traxxas servos back in the day and was surprised by how hot they got, but I don’t remember if there was any weird behavior experienced from it. Still running that 635 PM servo? I wouldn’t think that would overheat, but who knows on a track like that in a 1/7 Lim?

 

[gotnitro]

Could be you hit the LVC. Even though you have it cut off low, you might have had enough sag to trigger it.

Resting batt voltages come back a little bit, how long before you pulled these numbers was that batt sitting?

 

[LibertyMKiii]

I wonder if it is the temps? The ESC temps were clearly trending up till it shut off...

On this 134mph 3s speed run the temps were headed towards melt down and it shut off the ESC. Notice I had a solid red bar on my graph where it fully shut down.
I was also pushing it waaay too hard at 666 amps.

The car remained powered off for several minutes (in the center of the highway) and once powered back on it was still up around 150+F

 

[kaladeth]

Going out on a limb here, but would an overheating servo cause this? I’ve experienced some heat on older Reedy and Traxxas servos back in the day and was surprised by how hot they got, but I don’t remember if there was any weird behavior experienced from it. Still running that 635 PM servo? I wouldn’t think that would overheat, but who knows on a track like that in a 1/7 Lim?

I think the servo is fine. Yes still running the Promodeler DS635BLHV. I was checking it too it didn't seem that hot or so I thought (maybe max 120oF?)

Could be you hit the LVC. Even though you have it cut off low, you might have had enough sag to trigger it.

Resting batt voltages come back a little bit, how long before you pulled these numbers was that batt sitting?

I thought about that, but if it's LVC, you usually get into limp mode where you can still steer and have limited throttle. I believe I've hit this once before on the Limitless and was able to drive the car back to the pit okay (there is a noticable decrease in power output, not a sudden stop).

I wonder if it is the temps? The ESC temps were clearly trending up till it shut off...

On this 134mph 3s speed run the temps were headed towards melt down and it shut off the ESC. Notice I had a solid red bar on my graph where it fully shut down.
I was also pushing it waaay too hard at 666 amps.

The car remained powered off for several minutes (in the center of the highway) and once powered back on it was still up around 150+F

View attachment 362529

Yes that's the main hypothesis at this point. Here are the two A-Main rounds side by side. The steadily climbing temps are visible right up to shutdown:

Waiting to hear back from Castle support too. If that is the case, I have a few options:

• Improve airflow and cooling (cut holes into body, install better ESC fan)
• Gear down from 19t to 17t maybe?
• Try a MAX6 combo and see if it performs better
• Others?

 

[Dan B.]

I think the servo is fine. Yes still running the Promodeler DS635BLHV. I was checking it too it didn't seem that hot or so I thought (maybe max 120oF?)



I thought about that, but if it's LVC, you usually get into limp mode where you can still steer and have limited throttle. I believe I've hit this once before on the Limitless and was able to drive the car back to the pit okay (there is a noticable decrease in power output, not a sudden stop).



Yes that's the main hypothesis at this point. Here are the two A-Main rounds side by side. The steadily climbing temps are visible right up to shutdown:

View attachment 362624

Waiting to hear back from Castle support too. If that is the case, I have a few options:

• Improve airflow and cooling (cut holes into body, install better ESC fan)
• Gear down from 19t to 17t maybe?
• Try a MAX6 combo and see if it performs better
• Others?

I saw again in your build thread that the ESC fan is basically right up against the lid. Also, your temp on the logs was 170°? So yes, under load it isn’t too much of a stretch to surmise that the temp spiked enough to thermal. Next time watch for blinking lights for sure! If you’re concerned about aero you could fit a backwards facing scoop above the ESC so it could breath, or just a 40mm square cutout above it. I’ll bet that would do it. What were ambient temps on the track?

 

[LibertyMKiii]

Yes that's the main hypothesis at this point. Here are the two A-Main rounds side by side. The steadily climbing temps are visible right up to shutdown:

View attachment 362624

Waiting to hear back from Castle support too. If that is the case, I have a few options:

• Improve airflow and cooling (cut holes into body, install better ESC fan)
• Gear down from 19t to 17t maybe?
• Try a MAX6 combo and see if it performs better
• Others?

Honestly I don't think any ESC can run cooler than the XLX2. Probably just a matter of adding some better cooling to it.
If space is limited you may be able to run a fan across in stead of on top of it.

 

[King blitz]

So this happened once during qualifying yesterday and twice today in the main race. The car would be running fine for 10+ laps, and suddenly I would lose all steering and power. If you turn off the ESC, and power up again, the car seems to be perfectly fine and keeps going. On all three occasions I think the stop was accompanied by a little bump (into the center island or on a kerb) but it might just be because I already lost control.

On all three times, the radio battery was OK (hardly used), the car batteries were still > 3.7V, and the temps when checked with a temp gun seemed to be okay. I unfortunately do not remember if the lights on the ESC were flashing any code.

Here's a plot of today's last run:

View attachment 362504

Is the "Temperature" the ESC temperature (different from Motor Temperature), and is that what's causing the seeming shutdown?

I have a pretty low Cutoff Voltage, and Motor Temperature Cutoff is disabled:

View attachment 362506View attachment 362505

Any suggestions on what to adjust so I can avoid this in the future?

I'd check your lvc settings

 

[jbeech]

You can troubleshoot by running the receiver and servo off a 2S pack. These fundamentals never change, begin by eliminating components until you suss out the issue. I do all but beg folks to abandon the toy-like scheme Traxxas innovated 30 years ago of parasitizing control power from propulsion. Traxxas did it then to save, and do it today for the same reason. Note; no mention of performance as a reason. it's all about saving money. However, to this day, folks value convenience over performance. Can't be helped - sigh.

 

[Dan B.]

You can troubleshoot by running the receiver and servo off a 2S pack. These fundamentals never change, begin by eliminating components until you suss out the issue. I do all but beg folks to abandon the toy-like scheme Traxxas innovated 30 years ago of parasitizing control power from propulsion. Traxxas did it then to save, and do it today for the same reason. Note; no mention of performance as a reason. it's all about saving money. However, to this day, folks value convenience over performance. Can't be helped - sigh.

I’ve seen more and more builds lately that either use a standalone BEC or a dedicated battery to the receiver and not relying on propulsion packs via the ESC. The people doing that in the world of surface vehicles are a minority at this point, but interest in doing it “the right way” is definitely growing. Keep the faith, John!