What causes those "Instant On" ESC fires?

[ta_man]

Been using Castle ESCs for 4 years or so now and had my first catastrophic failure (MMP) this past Saturday.

Car & history:
Running a CRT.5 with RC-Monster chassis powered by a MMP controlling a Novak HV7.5 or HV6.5 with a Racers Edge 30C 3400MAHr 3S LiPo. This car is only used for racing, running our 1/10th scale Truggy class. Class ran 7 times this season, total of 18 heats & mains plus some practice, for a total runtime on the system of about 2->2.5 hours.

The Event:
This Saturday, ran my first heat, no problems at all. Second heat, put the car down at the end of pit lane and walk up the steps to the top of the driver stand. Give it a little throttle to move onto the track but it doesn't move. Turn the wheels left and right to see if it was still on or there was a radio problem. Wheels turn so I give it a little (emphasize "little") throttle again. Flames instantly erupt under the body (what I meant by "instant on" fire) which I can see through the windows. I yell "Fire" and a buddy of mine runs to the car, takes body off and yanks on battery wires - which pulled right off the battery ESC connector because the solder melted! Wires also pulled out of ESC side of connector and positive battery wire also came out of the ESC.

So what causes stuff like this? Is my 30C rated battery not enough? (An aside: a buddy runs a SCT Pro system on an OFNA 4wd SCT with one of these packs.) My gearing was 13:46 with the HV6.5 (running in "blinky" mode) which ends up at a calculated 38 MPH (loaded KV of 3000, from prior experience with this motor) and doesn't seem excessive. Setup was always good for more than 10 minutes of runtime (ran a 10 minute main and still had juice left in the pack). Motor temps usually ran around 120F and the ESC never seemed warm (fan was never ran except at startup).

Is this combo overstressing the MMP? I ran last year with a Novak Havoc 3S but that needed an external BEC (and thus two switches) so I changed to the Castle ESC with the switching BEC. MMP programming was left at all defaults except to reduce brake strength. The system had enough power for racing so I didn't need to play with the settings and was running in "Blinky" mode (no timing advance). I put under 1500 mAHr back in the pack after the first 5 minute heat, so my average amp draw can't be more than 18 amps. Battery never gets warm in normal use (of course it puffed because of this short).

One possibility occurs to me. A few weeks ago I was running the HV7.5 in a race and, because of dirt, the bearing seized and the car stopped. When this happened, I did not try to give it any more throttle. I just picked it up, brought it back to the staging area and checked it out. Neither the motor nor the ESC was hot. Found the seized motor bearing and swapped out the HV7.5 for an HV6.5 (going down a tooth to the 13). Ran the HV6.5 for the rest of that race session (another 15 minutes of race time plus 5 mins of practice). Then ran the HV6.5 another race day before this past weekend for a total time of about 1/2 hour+ on the MMP/HV6.5 combo. Could the ESC have been damaged by the frozen bearing and run for another 30-40 minutes before deciding to give up?

[_paralyzed_]

Nothing is forever. While electronics in general have become very reliable, especially in recent years with new technology, everything everywhere will fail at some time or another.

And flukes. A million units might have an incredible long life span, and a few dozen from the same batch will fail instantly, or at some random time.

I hate seeing the term "bulletproof" used on mechanical items. Everything fails at some time.

It is impossible to design an electronic device that will last forever, and the more you use elelctrical items the bigger the odds are that you will see failures.

[_paralyzed_]

Also- your battery is fine. Just check the temps (like you are) and if temps are reasonable you have done everything you could to safeguard your system.

After that it's a crap shoot