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Old 11-02-2008, 01:56 PM   #1
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Default Brushless Theory... I'm stumped.

So I head out to practice with my 8ight E. The battery is fully charged from yesterday, and I've got a decent set of tires, I'm ready to go, or so I thought. The first few laps, things go just as they did at the last race, perfect. Then it starts to slow down, like I'm out of juice. I put the battery on charge, and it's over 15 volts. I check it on the balancer, and all the cells are equal. Hmm, maybe it's not the battery. I'd already checked the ESC and motor temps, well within spec(140 on the motor, 130 on the ESC) It's got a ton of off the line power, but as soon as it starts rolling, little or no power/speed, as if the battery is dead. I check again, voltage good. We put a voltage tester on the battery leads and hit the throttle, plenty of voltage. Hmm...

So I give up and take the car back to my shop. I try a few things, programming card, radio calibration, etc... nothing solves the problem. So I try to reset the ESC itself, and initially, it seems to be on the 5S profile(I'm running the Losi 4S 5K mah pack). Hmm, I never changed it, so I change it back. I get the same lame performance. As I'm messing with it, wheels spinning free, I shoot the temp gauge at the motor, it's HOT, like 150 ish... I keep messing with it, and suddenly, the motor is running reverse rotation! Now WTF?! So, knowing what I know about brushless, I swap the leads to the motor. Now it's going forward, but seems to have the same issue. Killer... explosive off the line, then poof, it's slower than a T-spec! According to the blinking lights on the ESC, I have everything right. Did I brake the motor? I'm hoping I've just got the programming all goofed up. I ran through the instructions, but it's not working. I plan to call Tech Support when they open in the morning.

What sux is I have a race this coming weekend. So if my motor or ESC suddenly took a dump, I'm out of the race. I was pretty frustrated with it, so maybe I just missed something. I couldn't get the ESC programming software to install on my PC, so I'll try another one. Maybe there's something going on that I inadvertently caused...
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Old 11-02-2008, 02:43 PM   #2
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sound like 1 of the 3 motor leads has a bad connection.I had it happen once in my 1/10 truck.1 of the motor leads was unsoldered from a bullet connector I had in line so I could change motors without soldering at the track.It was fine off the line , but fell on it's face at the 1/3 throttle point. Worth investigating, I may be wrong.
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Old 11-02-2008, 02:47 PM   #3
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how smooth is the motor at low RPM?
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Old 11-02-2008, 03:19 PM   #4
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Worth investigating, I may be wrong
I appreciate any suggestions. The system was working perfectly, just not sure if I slipped, and pressed the program button turning it on... The motor leads seem good, they aren't getting hot, a sign of resistance. I can swap them because they are basically Banana type plugging into the ESC, but soldered onto the motor. I thought maybe the solder between the leads might have melted, but they look good too. I even pulled the heat sink off to look and see if I had melted anything, and nope, they look perfect.

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how smooth is the motor at low RPM?
It will cog pretty badly if you try to roll into the throttle super slow and with very little movement. But if you give it at least 1/8th or so throttle, it's fine, and smooth from then on. For whatever reason, for the first 10th of the acceleration, it leaps like its gonna work right, then falls on its face. I thought, maybe I cooked a capacitor, or my battery suddenly took a dump. Both seem fine, but I'd like to get Tech Support on the horn to see what they suggest. I've read about others having issue with their Excelerin systems, but theirs just quit working. Mine works, but feels like a 380 sized motor in a monster truck!

The fact that the motor gets so hot so suddenly, has me curious about the motor itself. I was well within operating temps up to this point, really not sure what's going on now. It could be as simple as having the wrong program... darn it! lol
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Old 11-02-2008, 09:07 PM   #5
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Be careful about running the motor unloaded for a long period of time. It is not good for the ESC.

I had one run unloaded for about 3 or 4 minutes while I was struggling to get it programmed. It just quit, so now I have to get it sent in. (It was an SS Novak.)
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Old 11-03-2008, 08:23 AM   #6
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I talked to Tech Support this morning. It's getting boxed back up and sent to IL for warranty repair.

Before I gave up last night, I got it to do some pretty weird stuff. First, it started running backwards... I didn't reverse the motor leads, it just did it on its own. I swapped them, to see if there was something wrong with the motor, and it will run forward, but the motor got pretty hot. So I swapped the leads back. Now when you turn it on, it'll run for about 1 second. Then, it just cogs. I've checked and rechecked my battery, and I'm pretty sure that's not it. So, it's headed off to service, and I'm trying to figure out what to race this weekend.
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Old 11-03-2008, 08:50 AM   #7
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I talked to Tech Support this morning. It's getting boxed back up and sent to IL for warranty repair.

Before I gave up last night, I got it to do some pretty weird stuff. First, it started running backwards... I didn't reverse the motor leads, it just did it on its own. I swapped them, to see if there was something wrong with the motor, and it will run forward, but the motor got pretty hot. So I swapped the leads back. Now when you turn it on, it'll run for about 1 second. Then, it just cogs. I've checked and rechecked my battery, and I'm pretty sure that's not it. So, it's headed off to service, and I'm trying to figure out what to race this weekend.
Hi, have you checked if you have turned the screws too far into the motor such that the windings are shorted?
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Old 11-03-2008, 09:23 AM   #8
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I didn't check that, the motor has never been off the car before. I did slide it out pretty far to get the new pinon on, but beyond that, the mount has never been removed, and this happened mid run. It basically slowed more and more, as if the battery died. I'm thinking it either shorted internally, or the programming is all screwy. I give up for now, Losi Tech Dept gets to take a shot at it.
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Old 11-03-2008, 03:25 PM   #9
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that sucks to hear. Do you have access to another motor to test with the ESC or are you the lone gun at the track with a 1/8 scale brushless setup?
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Old 11-03-2008, 03:28 PM   #10
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Well, I started to hook up my Novak 4.5, just to see if it would spin. But I feared the issue was with the ESC, and the last thing I want to do is break that motor too! I shipped it off today; should arrive at Horizon's Losi Tech Dept. by Thursday. If all goes well, I might have it back in a couple weeks. If not, I have to go buy some nitro fuel!
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Old 11-03-2008, 05:58 PM   #11
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i did something pretty 'tarded on a sensorless system once.... i thought id make it look "neater"by braiding the three motor wires together,as they were pretty long.when you do that it really seems to confuse the esc.

anyways,thats too bad hope you get it fixed!
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Old 11-03-2008, 06:11 PM   #12
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Originally Posted by dethklok151 View Post
i did something pretty 'tarded on a sensorless system once.... i thought id make it look "neater"by braiding the three motor wires together,as they were pretty long.when you do that it really seems to confuse the esc.

anyways,thats too bad hope you get it fixed!
In reality, you did confuse the ESC. Even sensorless ESCs are sensored. Instead of using a separate sensor array and cable, the sensorless ESC picks up feedback voltage generated on the windings by the magnets of the rotor passing by them. Look up Faraday's Law on the internet for an explanation of this. By braiding the wire, you actually caused phase cancellation of this feedback voltage. Preventing the ESC from properly detecting the rotor position.
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Old 11-03-2008, 06:14 PM   #13
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Quote:
Originally Posted by R40Victim View Post
I talked to Tech Support this morning. It's getting boxed back up and sent to IL for warranty repair.

Before I gave up last night, I got it to do some pretty weird stuff. First, it started running backwards... I didn't reverse the motor leads, it just did it on its own. I swapped them, to see if there was something wrong with the motor, and it will run forward, but the motor got pretty hot. So I swapped the leads back. Now when you turn it on, it'll run for about 1 second. Then, it just cogs. I've checked and rechecked my battery, and I'm pretty sure that's not it. So, it's headed off to service, and I'm trying to figure out what to race this weekend.
Sounds like the ESC had a bad phase. One of the three sections of FETs may be malfunctioning. I had a similar problem with a different brand of ESC, but they all operate on the same principle.
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Old 11-03-2008, 09:25 PM   #14
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I thought about that, and looked at the FETs (removed heat sink), and no apparent damage. I'd seen a pic online of melted FETs...

I sure hope I can get it back soon, and that this is a minor bug to work out of a brand new system.

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Old 11-04-2008, 07:06 PM   #15
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The damage may not always be visible to the eye. Good luck with everything.
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