MMM v3 up in flames!!!
 

Well... title says it all. Gorilla Revo, 6-cell, 2200kv castle motor. I was at the track today and wanted to try out the new combo as well as the one-way from RD I just put in. Happened to forget a jumper that allows me to use just one 3 cell, figured it's rated for 6-cell so I decided to run it with both packs. about 1.5 laps and the smoke started to come out and then some brilliant white/yellow flames shot out about 4 inches tall! With a little luck I was able to remove the power before the lipos were effected. So now it's in the back room stinking it up! Castle will be getting a call Monday!

i think your the first to have a v3 who caught in fire...sorry for your lost....maybe the positive and negative bullet plug had toutched the heatsink..so castle offer a good service..like you said call them .they will replace your unit for sure:yes:


im really think that the v3 is a solid esc (30hours each of my 7mmmv3)

yeah, but the v3's don't have bullet connectors on the power leads, at least not mine and my buddies. I know, the heat sink seems like a bad idea rubbing against the bullet connectors. But after telling Bernie about having to open my v2 and pry the heat sink away from those connectors to get it to work again, he said they've bench tested them and it's fine. I'm glad they offer great service. that's one of the main reason's I own so many Castle products.

Mmm V3
 

Mine also fried after converting an OCM Kaos buggy on BL. I ran it didn't seem real fast at the topend. I charged the batts just to get a full charge, plug the batts connector then the smoke came out. I was waiting a long time due to the conversion and weather sub zero temps and rain. Now I am sending it back for repair. I might have to get another one so I can see how good my conversion turned up to be.

Were you geared for use on 3 cell lipo? What was your rollout?

I was using the pinion they come with on a 70t spur. Mine is a Fastlane 2 speed tranny, I had it in low gear since I wasn't able to run on just 3 cell. It had a ton of power for that lap and a half. For tires that don't like to wheelie on clay, it was making it stand up on end; can't even put the hammer down on the strait-a-way. I'm a bit curious what you mean by "rollout".

Rollout, the final drive of the vehicle. Motor spins 30 times per 1 revolution of the tire = 30:1 rollout.

OK. the rollout looks to be right around 28:1. of course it would seem that this "rollout" test doesn't take the tire diameter into account. I'm using the Duratrax RT-X27 tires that claim to be 5.5" OD. So it'll be a bit lower "geared" than if I were running big 'ol 40 series tires that can be around 7" OD.

You can also figure rollout in relation to the tire. Just figure out the circumference of the tire, then you know that it takes 28 motor rotations to travel 17.27" on 5.5" tires. We can assume no ballooning for now.

Said another way, it takes 19.44 revolutions of the motor to roll one foot.

So assuming 4v/cell under load we have 2716 feet/ minute speed. Close to 1/2 mile per minute or 30mph. Seems very reasonable gearing to me.


Running 40 series tires with 7" od we can just take that 30mph and multiply by (7"/5.5") to get 38mph. Still very reasonable.

BTW: all this tedious math is what the R/C Calc site does.... :wink:

wow, you're taking me back to high school here with 2pi(r) and cross multiply divide! Even though it was pretty insane to have on a smaller track, it was pretty tame for what this system is supposed to be capable of.

The tedious math is the fun part!

had a nice little talk with Thomas from Castle today. of course, another one is on the way. but he suspects my batteries were allowing ripple current since the red power wire was the first wire to unsolder itself. seems plausable. 5000mah 20c zippy's. they worked great on my v2 and Nemesis motor as just 3-cells before.

ripple currents? did he explain what that is or how it happened or how to prevent them?

Ripple current is from batteries that drop voltage under load. Causes a ripple in voltage and current. If the batteries are bad enough that the Caps can't keep up, things get hot really fast.

Quick electronics lesson:

Caps have two functions: To pass/block certain AC frequencies (like in audio crossovers, oscillator tank circuits, timing, etc) and storage (like filtering power supply output). ESCs are using the main low-ESR caps (Equivalent Series Resistance) in "storage mode".

All caps have a "resistance" and when you quickly charge/discharge a cap at high current (due to the motor), the resulting high charge/discharge currents ("ripple current") along with the caps resistance creates heat. Lower resistance means less heat.

Lower quality batteries will drop voltage under load more, causing the caps to charge/discharge deeper which increases the current flow (and heat) in the cap. But, even low-ESR caps have limits and if they have too much ripple current, they will overheat and not do their jobs. Component failure and circuit instability can result.

So, you can either add in a bunch of extra low-ESR caps to help compensate, or just use a better quality battery that drops less under load.

EDIT: All that and JRH answers the question in less than two lines. :oops:

I find it strange that only the Mamba Monster is having this problem. This might also have been the cause of the Schulze ESCs to go up in flames as well. I haven't heard this happening to any other brand of ESC (I might be wrong). There's got to be something else causing this problems. You can't just blame the batteries. I had my Schulze go up in flames, but with the same set up no other ESC has done that. Even though the Zippys might use lower grade lipos they are still better then NiXX, so will the Mamba Monster fail all the time because the NiXX can't supply enough current?

I'm just curious as I still haven't used my Mamba Monster, but I would like to know if something else is causing the problems.

I like your explanation better Brian :D More informative. If we really wanted to get into it, we could explain how switching frequency affects ripple current, along with wire lengths and battery quality. I don't have a silly scope to make those measurements with though. Easy way to explain it is that ESCs get hotter under partial throttle, and ESCs run cooler under full throttle.

I have seen plenty of mamba's and sidewinders go up in flames too. The only way to REALLy figure out what is going on would be to hook his setup onto a scope and run the rig under load.

Although, I think the hotter ESC with partial throttle is more due to the PWM signal and FET slew rate than anything. At WOT, the FETs get switched on and off far less times than when at anything lower, and so the slew rate losses are reduced.

I think that the more recent Castle ESC's (sidewinder/MMM) caps aren't as big or capable. I know when using Nimh on a sidewinder or Monster it'll cause the radio to cut out; requiring a glitch buster. whereas the Mamba Max seems to work great no matter what. Not sure if it's related, but I have a feeling it is.

Mmm V3
 

So if I add like one 2000 uf 35V 105(HT)degree caps on the input side will there be any side effects on doing this, bad or good. Thanks for the great info.

Adding more caps can't hurt. Don't know if they will help too much if the battery isn't up to snuff. If you added a total of 1F (1,000,000uF), then you could get away with lower quality batteries since it will absorb the high current pulses. :smile:

The only downside to larger capacitance is that you'll get a larger spark when you connect your battery to the ESC...

Just wondering if that will cause the MMM V3 to fail. Thanks Brian, appreciate all the technical tips you are posting.

No, if anything, it'll help by reducing the ripple...

Nothing directly to do with the power caps this would be the bec voltage dropping or interference.

Indirectly it might be the bec dropping voltage as the input voltage dropped very quick which wasn't smoothed out by the power caps but if you are getting to that point your esc would be suffering with the bad batteries and close to smoking!

Hope it helps
 

http://i328.photobucket.com/albums/l346/clowkoy/cap.jpg:lol::party::whip:

Caps
 

Wow, I used to have those caps long time ago. Just make sure you don't accidentally short nothing out. Maybe you can even run AA nimh with one of those.:yes:

Just be sure to give those AAs a little while to charge that thing. :smile:

yeah and then charge them back up:wink:

Awesome.