Krio

iTrader: (159)

What speed control are you using? And what settings?

If you can hold your finger on it for even a half second without getting a burn, it isn't too hot. Something else is wrong. Do you have a temp gun you can borrow to confirm its exact temperature?

NedHogan

Thanks. It's a 120a HW sct Pro. Punch as low as possible. Lvc 3.2v. 0 timing. Haven't tried removing the sensor cable yet. My last esc was 60a and sensorless. It would overheat or at least stop for a break after about 10mins or so.
I'll aim to get a temp gun.
The car rolls very freely and all wheels turn without resistance. The only thing is the dog bones and outdrives are old but wouldn't think they are causing to much problem. The gear mesh is almost too loose.
Batteries are 5000ma 45c Peak racing
I am starting to think the it might be the Lvc but I don't think the batteries are 'wrong'. They should be good for 225a. And they do not get warm. Also no wiring gets warm that I have noticed. Had a dirty connector one time that heated the battery wire but that's clean now and cool.
I have heard the sct Pro can be funny with its Lvc.
Any ideas are welcome.
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Krio

iTrader: (159)

My initial thought is that the batter just isn't up to the task and is tripping the LVC. You can't really trust the C rating of a pack at this point and most packs rated under 60C are low end packs and ones rated 80-120 are high end packs. That's about all the C rating can tell you without more extensive testing. Also, the pro4 motors can easily pull a couple hundred amps at low rpm for a split second. It's interesting that your 60A esc could go longer before cutting out, though.

Do a test run without the sensor cable. Sensorless operation will be closer to the optimal timing than the sensors, so it should run a bit cooler. At the same time, it won't cut off due to temperature because it will lose access to the temp sensor in the motor. I would have a temp gun on hand just to check every couple minutes that it is staying under 180 degrees F. Do you have someone you can borrow a battery from to compare?

NedHogan

Thanks for the reply. I will probably buy a temp gun some time soon but in the mean time I think I will try a couple of different things to get to the bottom of the cutting out, like lower the lvc to 3v or remove the sensor cable etc. To narrow down what it can be.
Apparently the HW SCT Pro esc doesn't monitor motor temp so that is one off the list.
Also apparently that motor is expected to run quite hot (not my main concern at the moment. Obvs not over 180f)
I wonder whether the old sensorless 60a esc as it didn't alter timing couldn't make the motor demand quite as many amps therefore lasting a bit longer before cut off. Saying that I am a bit confused as to what the sensor cable is for on my sct Pro esc if you keep the timing at 0deg as I have; you'd assume it isn't doing anything but at low revs it does seem smoother with it.
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NedHogan

OK so it is definitely the lvc as I lowered the cut off to 3v and it was much more consistently lasting at least 5mins on 4000mah batts. The red light was flashing each time it died.
It was barely lasting 3 laps before.
Need better qual batteries (or a gentler motor) as I measured the voltage as soon as in the pits and it was 7.3v and each cell equally charged therefore they are dropping voltage under load.
Would be interested to see what HW motors are like on amp draw compared to the pro4 motor or whether mine has been heat damaged compared to an off the shelf pro4 motor.
I have heard on other threads that a 5000mah 30c batts lasts fine for some people in an losi scte using a 3800kv motor. It shouldn't be a million miles away from a 4000kv motor. Then again others say you have to have a 7000mah 70c plus.

NedHogan

Also it runs cooler without the sensor cable.

Tekin Prez

4wd drive shortcourse is the hardest load in RC !! It is basically 1/8 buggy but with only 2S lipo... so it pulls double the current. A dumb setup to say the least and a mistake in my opinion that the rules require it. This is part of the reason the class struggles and has died off in many areas. Too hard on batteries. If your area will allow it go to a 3s or prefer 4s setup with half the kv motor and you will be much happier.

Yes the motors run cooler without sensor cable, sensorless mode, with most esc's. 4pole motors do not need any timing, and in fact do not like it and it just causes extra hear. If you use Rx8 it will run the same as sensorless but still use sensors to get a smooth start. Our dual mode automatically changes to sensorless mode once moving.

Krio

iTrader: (159)

Unfortunately, KV only tells part of the story and you can only use it to compare motors that are from the same line under the same manufacturer. The battery voltage you measured was without any load on it. Keep the voltmeter on, hold the bumper, and apply some throttle to put a strain on the system. You'll see the voltage dip a ton. The fact that you could read 7.3 in the pits but it was cutting off at 6 tells me that particular pack isn't great. I'd bet you a good chunk of change that a new, quality pack will erase all your issues. Look for something over 6000mah and 80C or higher. I used these packs in 4wd SCT without any issues in the past: https://hobbyking.com/en_us/turnigy-...-approved.html

jlog

iTrader: (1)

Sorry if this has been discussed further back in the thread but has the current limiter been discussed? We I use to tune for many 4x4 SCTs I would dial that way down and drivers went faster and the guys who paid attention NEVER burned up any thing. My drivers on the east coast found that turned down to 45 worked great for them. Here in Michigan 65 was the magic number. The Tekin ESC has some many tuning options that will help you excel past your completion. Enjoy the hobby and explore what this ESC really has to offer.

Krio

iTrader: (159)

Hey, good to see you on these forums again. Making a return to RC?

Ned is using a different ESC, so I haven't brought up the current limiter since I'm not familiar with the options on his speed controller. I agree, the current limiter (now called torque control) is a tool not used enough by most racers.

jlog

iTrader: (1)

Not as of yet. There is a new track that is opening up a few miles from me in the summer and depending on the type of program they have I might. I just never want to get back to where I was before.
And I was just checking out old accounts and seen this thread and was hoping to help a little.

NedHogan

Thanks everyone. And thanks for the link. Those batteries seem a bargain for their spec. I have found it hard to come by such a high quality battery before.
Also yes 3s would be a good idea for these!

NedHogan

Well I got that new battery 7500mah and 90c by turnigy and that has pretty much solved all my problems.​