MMM Explodes into FLAMES! - RC-Monster Forums

jpoprock · 07.10.2009, 12:42 PM

Muted: WTF???? Whu happon? Just after arming? That's wild!

You know what guys... I remembered the other day that this last run where my MMM melted was NOT the first time I ran my Moabs. I ran them about a week before, on fine gravel, and ran it hard. It was sliding and skidding like mad. It was insane fun! I ran it much harder that time, then I did when it smoked. When it smoked, it was like half speed driving.

I still haven't looked in the tranny area, but I suppose there could some gravel lodged in there somewhere, causing binding maybe. I need to look still. But my MMM is off to Castle, so we'll see.

shaunjohnson · 10:42 PM

this is only what i have heard...i may have got it wrong but i'm sure one of the pro's will correct me...

i think your issue and muted's issue are related.

it isnt always the amp draw, it can sometimes be the braking that kills them.
when you use the breaks, power flows back through the MMM and into the battery, if the battery isnt a high enough AMP rating (say 80A cont or something rather than the recomended 150A) then the resistance causes the voltage inside the ESC to rize, in some cases this can destroy or damage the phase caps.
now when the phase caps die they seem to go quietly, like just before you finish off a battery pack and put it away.
the blown up caps wont always prevent it from running straight away, and the ESC can soldier on for a bit longer.

but next time you turn it on and it's armed itself, it trys to use hte caps and...oh no they arnt there...so BOOM

these problems seem to happen more often on 6s operation...because the voltage is already high so it is already getting closer to the 40v MAX braking voltage rating.

i belive the problem you guys both have might be related with the caps, jpoprock might have used the car a bit longer after hte caps went pop and as soon as the ESC needed the caps again...well....
but as for muted, i think his caps may have gone just before he brought her in for the day at the end of the pack or something, hence when he turned it on next time and hte caps were needed...fire

hope one of the more experienced guys can clear up weather i am right or weather i completely fecked up

sorry for the loss.
shaun

muted · 07.11.2009, 08:56 AM

Yea it was crazy. I just got it out of the car, connected the battery, turned it on, it made all the right noises, then when I pushed the throttle on, it cogged a bit, then started smoking, then snap crackle pop! A little fire shot out of it.
I disconnected the battery before even thinking about it, and my mate just started ripping the wires out of it. The wires ended up about 10 feet away!

Just turning it on, then 5 secs later turning it off, it shouldn't of even started to warm the battery, but even after 5 minutes, when we came back after searching for the wires, it was warm to the touch. Must of drawn some serious amperage!

When I took it out for a run the day before it ran perfectly, then the last bit before I went home it was cogging something severely. Took it home expecting to find some rocks caught in the transmission but nothing at all.

fastbaja5b · 07.11.2009, 10:18 AM

Quote:

Originally Posted by muted

Yea it was crazy. I just got it out of the car, connected the battery, turned it on, it made all the right noises, then when I pushed the throttle on, it cogged a bit, then started smoking, then snap crackle pop! A little fire shot out of it.
I disconnected the battery before even thinking about it, and my mate just started ripping the wires out of it. The wires ended up about 10 feet away!

Just turning it on, then 5 secs later turning it off, it shouldn't of even started to warm the battery, but even after 5 minutes, when we came back after searching for the wires, it was warm to the touch. Must of drawn some serious amperage!

When I took it out for a run the day before it ran perfectly, then the last bit before I went home it was cogging something severely. Took it home expecting to find some rocks caught in the transmission but nothing at all.

Was this on 4 or 6s lipo?

muted · 07.13.2009, 03:33 AM

Quote:

Originally Posted by fastbaja5b

Was this on 4 or 6s lipo?

Yep it was on 4s. The battery is a Zippy 4s1p 3500mAh. Stickered as 30c

shaunjohnson · 03:45 AM

Quote:

Originally Posted by muted

Yep it was on 4s. The battery is a Zippy 4s1p 3500mAh. Stickered as 30c

you must have had 2 of thoes packs wired in parellel right?

and as for the vast magority of 6s setups going bacg, yeah i guess it is pushing the envolope.
i run/race with 6s in my revo.
never had an issue but my setup isnt crazy either...not even trying to get speed runs.
geared 16/68 on a 3905 tranny and that equades to 40mph on std MTR tyres.
it just seems that people see 6s, and steriotypicaly assume it's ultimate speed and power with no drawbacks.

MABEY there should be a note in hte manual stating that 6s operation is recomended for advanced users only.

suicideneil · 07.11.2009, 07:11 PM

Quote:

Originally Posted by muted

When I took it out for a run the day before it ran perfectly, then the last bit before I went home it was cogging something severely.

You cooked and de-magged your motor, then the next time you used it > cooked esc.

Unless the motor wasnt hot after the last run, temps?