Did I kill my MMM V2?

[pasan]

I had a brain fart and hooked up 6S in reverse polarity to my MMM V2. Loud hollow sounding pop, very bright blue spark, and a mangled connector. So the obvious question is, have I killed it? I've attached a photo of the fried connector.

[pasan]

Please can anyone tell me if it's okay to give power (with correct polarity) to the unit? It was just one half of the edge of the connector which touched, and the ESC itself did not emit smoke nor the familiar odour of burnt plastic/ozone.

[BrianG]

TBH, I wouldn't try it. I would just play it safe and send it to CC with the appropriate check or M/O.

But, if you do get brave and want to try it, I would temporarily use a ~30A fuse inline with the power wire. That way, if the ESC is really bad and tries to pull gobs of current, the fuse will pop and you won't have to worry about flames. If all is well, hook it up without the fuse and see if it works.

Be warned though: even if the ESC doesn't pop the fuse on hookup, the BEC may have also fried and could send full battery voltage to your rx and servos. Before attaching other stuff, measure the BEC output as well.

[pasan]

Thanks Brian. I've got some automotive circuit breakers that I could use to test this. And I'll use my dying 6 cells packs instead of LiPos; I'm hoping 16 volts will suffice.

[BrianG]

Circuit breakers are too slow. Plus, they usually trip at around 125% of their value. Better to use a fast-blow fuse. 30A should be enough to handle the caps charging, but not high enough the let the ESC flame out.

[pasan]

Welp I couldn't find a dispensable 30A fuse anywhere, so I went ahead with the circuit breaker. All seems fine on 12 cells, the BEC shows a solid 6V at the outputs, all three LEDS are flashing in unison and the fan refuses to switch off because the boot sequence isn't complete until the thingy detects an Rx. Castle Link also works, I did a fresh F/W update and reloaded my saved curves. Tomorrow I'll attempt at driving the car with 12 cells, and then try it with 3S if all goes well.

[fastbaja5b]

My experience is a lot of the time reverse polarity kills the lipo not the esc

At least it did when I did the same thing on an LRP TC Sphere, speedy was fine, Lipo was dead.

[pasan]

The LiPos used during the incident are all showing 4.16V per cell (2S3S1P). There's no puffing either that I can see. I'll try them out tomorrow as they are.

[sikeston34m]

Originally Posted by pasan

The LiPos used during the incident are all showing 4.16V per cell (2S3S1P). There's no puffing either that I can see. I'll try them out tomorrow as they are.

I bought a used boat one time that had the deans connectors installed reverse polarity.

Well guess what. I plugged it up.

Lipos can discharge huge amperage. LOL

In my case, it fried the esc AND took out one cell in the 4S Lipo setup. The esc was a brushed esc.

I believe my lipos had something inside that was designed to let go before the battery had a melt down.

In your case, it sounds like you got lucky. Your Lipos are fine and it sounds like your esc is too.

Good thing you just touched it instead of getting it plugged in good.

[pasan]

Indeed, I have been extremely lucky with my MMM V2 so far. I hope it continues *knock on wood*.

[Sammus]

Yeah i've soldered on many a deans backwards in the small hours of the morning. A few of my ESCs have copped reverse polarity, all of them lived through it no worries :)

[What's_nitro?]

You may want to replace the capacitors on the ESC too. I'm sure they don't like being charged to full potential in reverse... Actually, that may have been what caused most of the sound/light show.