MMM v3 up in flames!!!

[BrianG]

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.

[lutach]

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.

[johnrobholmes]

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.

[BrianG]

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.

[mtfly2000]

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.

[transtalon]

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.

[BrianG]

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.

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

[transtalon]

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

[BrianG]

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

[Arct1k]

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!

Originally Posted by mtfly2000

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.

[transtalon]

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.

[BrianG]

Originally Posted by transtalon

...Maybe you can even run AA nimh with one of those.

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

[mtfly2000]

Originally Posted by BrianG

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

yeah and then charge them back up

[What's_nitro?]

Originally Posted by clowkoy

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

Awesome.