MMM V3 Dead Short on Lipo!
 

So I got my V3 from castle last week as a replacement for one of the dead earlier version MMMs I sent in. I went to set it up in the truggy on Friday night. It had a MMM V2 in it so it was just a matter of unplugging the motor and battery wires from the V2 and plugging them into the V3 and then mounting it into the truggy. Simple and very nice easy swap out. I like the 6.5mm sockets for this.

Anyway, I went to plug the battery in for the first time and the instant I touched the deans plugs together WHAP!!!!! I got a HUGE spark. I mean HUGE!! it melted the ends off of the deans plug prongs. Like the power of a dead shorted lipo. If you have ever dead shorted one by accidnet you know what I mean.

At first I was like WTF did I screw up. Thinking I wired something wrong or pluged something in wrong. After cleaning my pants out... I went back over everything to see if I could find what was wrong. I couldnt find anything, so like an idiot.... I tried plugging it in again. WHAP!!! another HUGE spark. Scared the poop out of me again even though I was mostly expecting it. Well now i'm pisssed an I pull the whole thing back out of the truggy and redo all of the wiring thinking something has to be screwed up even though it was the exact same wires and all that I had just unplugged from my V2 and they worked perfectly.

After redoing the wiring again, this time I figured I wouldnt punish my poor lipo any more so I got out an old 6 cell stick pack to try plugging into the controller. And again.... HUGE sparks. This time a bit less because the 6 cell NiMH didnt pack the punch of the 5000mah 5s lipo. Well at this point I just diconnected the motor wires and pulled it back out of the truggy. I figured the thing is just screwed up and I figured it was probably already fried so with the MMM just sitting on the bench not attached to anything else I attampted to plug the 6 cell NiMH pack back in just to see what would happen. This time the spark was a little less than the previous time. So I tried it again and a little less spark. After 4 or 5 more times plugging it in I got no spark at all any more.

At this point I figured the thing was probably dead, but Id try it and see anyway, and to my surprise it fired right up. I ran it on Saturday at the track for about a pack and a half and it all ran normal with no issues.

The only thing I can guess is I got one with the heat sink dead shorted against the battery input 6.5mm sockets and when I plugged in the battery it was a dead short and after few good jolts it just burned away the heat sink aluminum like Patrik said it would on a different thread around here.

So now it seems to be working normal, but I have very little trust in it and I am now wondering what kind of long term damage the dead short did to my lipo. It didnt swell, but I know I have had a pack in the past that I accidentally shorted out for a slpit second and it didnt last nearly as long as its matching pack that was never shorted out.

I'm rather pissed about all this, and I'm not even sure that it was the heatsink causing a short, but its my only guess since I cant open it up to check anymore without voiding my waranty. And I'm certainly not going to void it on this one after what it just did to me.

Just wondering if anyone else has seen anything crazy like this. I'm gonna try and call CC tomorrow about this. I had a nuts day at work today and just coulnt get the time to do it today or I would have already called.

Wow...that's seriously bizarre. Sounds like a manufacturing defect...maybe a stray blob of solder? Patrick's insistent that the heatsink couldn't cause a short like this, as it would just ablate almost instantly...though CastleMike said he was also going to work with manufacturing to prevent any more touching plugs.
Castle won't have a problem with you opening up the case to take a look, as long as you're careful about it.

I'm gonna wait for them to tell me that at this point.

When i'll recieve mine, i'll take a multimeter and test the conductivity between the plug and heatsink:gasp:

Fair enough.:wink:

They said in the other thread that if you open it carefully, they will warranty it. They have had a problem with Traxxas forum members :oh: jamming screw drivers into the ESC to open it damaging the brain board.

I know it was said that on the motors it wouldn't hurt, because the resistance in the motor is lower that the alumnium. But the battery is a different story, Is the resistance of the whole esc low enough to redirect a dead short on the leads? From what i can see, this is the absolute worst case, But it does show that the dead short testing at castle, that the esc would survive, that is a good thing

Well, I have the same problem with the positive bullet touching the heatsink. I'm just going to run it this way and like you, I don't trust it either.

http://www.rc-monster.com/forum/showthread.php?t=16432

I just got a shipping notice from Castle today. Maybe I'll connect it to the 2 Optimas in my 1:1 truck to the Monster first to make sure everything is nice and ablated before I connect a lipo to it.

:lol:

what?:oh: are you trying to say that the members on the cough "idiot forum" cough would acually do that?? no way:lol:

Yeah... I find it hard to believe too.:whistle:

Just bend the heat sink fins away from the bullits, put some shrink tube on them & run it. At some point Castle will listen to us about this problem (& the fan wire issue).

My v2 did the very same thing!

I had it all set up and drove it for about 10mins in our caldisac, at 10pm at night...I then came in and updated to the new 120 version film ware....the next day I was about to leave for the track and I thought I had better try it be for I leave. I pluged in the 5s flight power( the same pack I ran the night before... I turned on the power switch and:gasp: melted the wires off at the conector to the battery and conector at the ECS, melted the shrink wrap along the side of the battery pack where the one wire runs the length of the pack..:cry:

I then checked the + - post on the ECS and there not touching.

I got one more pack and touch the conector and VERY large sparks... I didn't even bother messing with it, as I had one other to send ...I packaged them up that night and OFF they bolth went to castle.

Yes this 5s has gone down hill fast.. I have only 4 cycles on it since this happend and it's very soft now.

that may not be enough in any case. sometimes the plugs touch the heatsink not only on the fins but also at the bottom plate of the heatsink. so you can not just slip some heatshrink around it after bending the fins away.

this is all interesting information. short the esc to burn away the plugs from the heatsink before you can use it properly....:oh:

bye
rhylsadar

And that was my issue with it since I noticed that when I inserted the male connector, undue load was being put on the female connector as it was being forced away from the heat sink.

At least mine didn't give those sparks.

\


and then they void your warranty and your stuck with a dead v3:diablo:

V4 MMM here we come...

Wrong, I did not open the case or solder on the board so how could my warranty be void. :na:

I don't think castle is that stupid.... yet...

how did you bend the heat sink fins?

Just push the close ones away from the bullit. They are very soft & bend real easy.

Talked to CC. Tech support guy agreed that it was probably a short accross the heat sink. They are sending me out a replacement. He told me to open up the case and just put a little shrink wrap around the 6.5mm socket. But there isnt any room to do it. Its tight against the plug. Looks like they are using the solutions developed on here as their tech support solutions now. LOL

Hopefully this one is good. I'm really getting tired of this.

good to read..i hope cc could fix this kind of issue:yes:

why ???the v3 old so far...simply other kind of problem come out....

Chicken Little...

:lol::lol:

im hard on the mmmv3 and the only thing that ive broke is



























......DRIVING SHAFT:whip:(traxxas c.v.d and plastic driving:surprised:)

Come on castle....please get it right!!! If I have to buy a 400.00 mgm for everything I own I'm gonna wind up in the soup line at our local shelter!

Which is what he should've done after the very first spark.

:lol::lol:exact

Hind sight being 20/20, I agree. Easy to loose you head in the heat of the moment when the panic and frustration set in. LOL

I did throw a multi meter on it after the 2nd spark, and before the repeated sparking with the 6 cell NiMH pack, but got a really wierd reading. I couldnt get it to give me a consistent measurement. It started off with a very low resistance reading at almost infinity and then over a few seconds kept going up and up to a very high number. It was strange. I also measured the resistance between the plugs on the working V2 I pulled out of the truggy and got some "dancing" numbers. Not sure why that would be, but that little test basically didnt tell me anything. so I went back to the "brute force" testing . lol

What you saw was a capacitor charging up. In resistance-measuring mode, meters output a small voltage through a precision resistor and measure the resulting small current (actually it looks at the voltage drop across the internal precision resistor), and then use that to calculate the component resistance being measured. At first, they have ~0v (which would look like ~0 resistance to a meter). As the cap(s) charge, the difference in voltage is less, which reduces the current in the meter's resistor, which appears as higher resistance. At some point, the meter will read infinite resistance because there is no current flow. Actually, you could use this to calculate the meter's output resistance, but that's another story. :smile: Anyway, this is why measuring resistance is sometimes useless while the component is in a circuit.

The fact that you did see the resistance change tells me that there is no short circuit. But that still doesn't explain the "huge" spark. :neutral:

If the capacitors are at 0 volts, and you plug in a 5s pack, YOU WILL see a decent spark. That's normal, but usually the second time you try to plug it in there is no spark. Maybe there is just low enough resistance so that the capacitor drains rather quickly on its own and will always cause a spark every time you plug a pack in. Or maybe castle just decided to use mega capacitors on the V3s. Lol

No... It wasnt a normal spark. Trust me Ive plugged in more than my share of these things in my day. lol It was huge crack like when you accidnetally short a lipo. It melted the ends of the deans plug. It was like an arc welder not capacitor spark.



The fact that it works now is the thing thats totally freaky to me.

:rofl::rofl::rofl::rofl::rofl::rofl: :mdr:

Somehow that was one of the funniest things I've read in a while... :rules: sorry man!!! :whistle:

So this MMM is still working now???

Yep. Ran it again yesterday. 2 and a half more full packs through it and its still running.