MMM Explodes into FLAMES!

[shaunjohnson]

did you even read what i wrote?

[suicideneil]

Originally Posted by shaunjohnson

did you even read what i wrote?

Yes, you talk about blown caps due to over voltage, I talk about a dem-magged motor due to excessive heat, that then causes massive current draw trying to get the motor spinning; that much current will cook the fets.

Blown caps due to over voltage seems unlikely as:

A) Its a 25v esc, the caps are spec'd for 35v- I dont know where you're getting 40v from, but it aint happening. The voltage being put back into the batts as a result of regenerative braking is no more than a few mV, as proven by a nice eagletree graph someone did back along as a practicle test.

B) I dont need a B as my A was so great

The hot lipo packs would seem to support the 'massive current draw as a result of trying to turn over a dead motor theory'. Could be something else that is going pop though, but aparently castle (and HPI...) can access some sort of data recording chip inside the esc to do an autopsy....

[BrianG]

Originally Posted by suicideneil

...but aparently castle (and HPI...) can access some sort of data recording chip inside the esc to do an autopsy....

lol, an ESC "black box" (like they have in airplanes).

[shaunjohnson]

these type of failures MUST be caused by setups
i cant get my MMM over 150 (fan is on very briefly after stopping) under HARD load and on 6s.
but i also USE the punch control and the throttle curve so no standing backflips for me, it will wheelie if i mash the throttle but i avoid that cause the tyres cant take it (center diff)
my motoer never even hits 120 and it's geared for 45mph on 6s.

i wanted to go up to 40 series on the reace truck...but needless to say gearing down is on order, but then regen brake load is increased from the extra enertia.

and personaly i have never heard on anyone killing one of the castle/neu 2200's from overheating

kinda need a recomended setup in the boxes of traxxas and HPI since both company's are speed obsessed but in reality, unless treated nicely and you are running great lipo's then the future looks overcast...
and the standing backflip video's on HPI's forum...they cant have possibly done that geared for 70mph

[suicideneil]

Thats what I thought.. Mind you, that is according to the numpty on the HPI forum who blew up his flux the other week, so it'd be nice to hear from a Castle dude about said data recorder.

[TexasSP]

Better hush hush on the black box or the unmarked black suv's will be pulling in front of your house soon......

[jpoprock]

Honestly... I think that run I did on the gravel, with the Moabs... is what did the ESC in. I shut it off in the nick of time (unknowing anything was wrong), then when I drove lightly around the yard in grass, the caps let loose from braking. Not OVER braking, but just regular braking. The ESC just couldn't take it.

A friend of mine fried two MMM V3's (not fire), from driving them in sand he thinks. So, I gather that sand is NOT your friend with a BL system huh? I can't believe how touchy these MMM's are. Overgeared, too much braking, sand, low C rating, etc causes failure. I get it that there are certain basic rules that have to be followed.... esp when you're pumping 6s thru the thing. But now I'm going to be all paranoid when I get my new one back, and I should have to feel that way.

[BrianG]

TBH: I don't like running ESCs to their max voltage value. There just isn't enough headroom for me. The TVS on the MMM is rated for 26v IIRC, and at 6s, a system can generate enough EMF when braking to stress it and blow it. And when the TVS blows (which is probably not noticeable to the user), all that EMF energy is no longer being clamped and the FETs, caps, and batteries have to cope with it instead. I like to run 1s below the rating, so, for the MMM, that's 5s. No problems so far on either of my two MMMs. Even on a Quark (which is rated for 6s too), I run 5s max in any of those systems, and those have been solid.

The only ESC I run at over it's advertised spec is the MM (on 4s), but that is because I feel it is underrated. 25v caps and 30v FETs. The only limiting factor IMO is the built-in linear BEC, which is easily remedied with an external switching BEC.

Should the MMM be totally reliable up to its rated spec? Sure, but as said, everything has to be "ideal" when running that close to the edge. Any one thing out of whack can cause "issues" as we've seen. Why is it that some people (maybe the majority) can run fine all day long on 6s? I dunno, maybe they are lucky, happen to have cream of the crop components, or simply not as hard their stuff.

[e-mike]

¸¸¸¸ I don't like running ESCs to their max voltage value. There just isn't enough headroom for me. The TVS on the MMM is rated for 26v IIRC, and at 6s, a system can generate enough EMF when braking to stress it and blow it<<<<<<.





castle should put a higher devise to prevent some failure????

[BrianG]

Originally Posted by e-mike

...castle should put a higher devise to prevent some failure????

Maybe, but that would involve a total redesign. Not sure if they are willing or see the need for it. As long as people understand the limitations, 6s should be ok.

Besides, the reasons I stated are just MY opinions/theory. It doesn't mean they are correct. But, the evidence sure supports it. How many 4s or 5s setups have you heard of flaming up vs 6s setups? I'm sure there are some, but those are probably just the normal statistical failures.

[Arct1k]

FYI back voltage is a lot more than that the HV BEC can take 50v input for non braking air use but only 6s in cars due to voltage spikes under braking...

[BrianG]

It's like anything else that is high-performace; cars, computers, audio, etc. The closer you run to the edge of the envelope, the more chances for failure. Most people who fit this category understand this and expect failures, but these systems are made available to the average joe who thinks they can open the box, plug in any old battery, and gear to the moon for subsonic speeds. And those same people wonder why things fail.

I agree though, TRX and HPI should definitely provide recommendations for various uses along with warnings if the user departs from those recommendations. The trouble is that there are so many variables to account for; tire size, drive style, ESC settings, battery quality (real-world, not whatever sticker the manufacturer decides to slap on to improve sales), voltage, and so on. Would make recommendations either too general to be effective, or too detailed for people to follow.

It's nice that HPI and Trx has these systems available right out of the box, but I don't think the masses are ready for it TBH.

[jpoprock]

Hey guys... I can't take any pix, cuz my camera is at the in-laws! But I pulled my Neu the other day to take a look at it, and noticed something peculiar. Here is a picture from Neu's site showing the copper wires:

http://www.neumotors.com/Site/Picture_gallery.html#1

Well, on MY Neu 1515 2.5d /f, a particular section of winding is much darker... almost brownish black in color, and the other section of windings is the copper color. Like a 1/4" braid. If you took both colors and wrapped them like the picture shown. 1/4" section is copper, the next brown, the next copper, the next brown.

What could this mean?? Could that ESC fire have somehow burnt up my motor? Or did something go wrong w/ the motor causing the ESC fire??

I NEED MY CAMERA!

[suicideneil]

Bad motor > dead esc, not the other way in 99% of cases I've seen around here. Seems more like you may have gotten something nasty inside your motor, that caused a shorted phase > cooked esc. Running in gravel you say? With a motor that has lots of holes in both ends?... (Im a bastard, but at least I try to be humerous at the same time....).

[jpoprock]

Originally Posted by suicideneil

Bad motor > dead esc, not the other way in 99% of cases I've seen around here. Seems more like you may have gotten something nasty inside your motor, that caused a shorted phase > cooked esc. Running in gravel you say? With a motor that has lots of holes in both ends?... (Im a bastard, but at least I try to be humerous at the same time....).

Ha ha. Touche. I'm nearly positive that nothing got inside my can. I was running on gravel yes, but it wasn't like rocks were bouncing off the chassis. They were being thrown 20ft from the rear. Now... DUST was flying around, but dust shouldn't cause a motor to konk out should it? I mean... people race on DIRT which is far worse then the 10min gravel session I had!

I have a crap camera here I'll try and use to get a pic. But I have a feeling it ain't gonna be good news. I'm going to contact Neu as well.