Hi Doug

That cable was just a quick solution to let me connect the ESC to the battery without repeating yesterday’s fiasco while I sort out a fused link. After writing off about £60 of kit I’m just being ultra careful.

Hi Neil,
Sorry, but I don't think that your cable 'Switch' will cut the mustard.
If anything is wrong the damage will be done 💥 long before you can even think of reaching for it.
And those connectors are not so easy to get apart in a hurry.
What you need is a quick-blow fuse in the + (red) wire.
Fit a fuse rated at about 90% of the max rated current of the ESC or the motor, whichever is the lowest.
That will react a zillion times faster than you (or I) ever could.
A lesson many of us have had to learn the hard way☹️😭
Cheers, Doug😎

Hi Neil that certainly looks like a MOSFET and to the right is possibly the BEC chip. The MOSFET to the left has also burnt on the same three pins(drain). The single pin to the right is the gate control with the four pins on the other side of the chip being the source. It is possible to add protection and some of the better chips have built in protection. You could use a simple high current Schotty diode across the supply with a fuse between the diode and battery. If you connect the wrong way the Schotty will provide a dead short and blow the fuse (needs to be a quick blow type). It will certainly disconnect the supply quickly but not sure it would always be quick enough to save the electronics.
I think you will however now always stop and look to check all is correct before connecting a battery, I know I do.
cheers
Dave976

Removed some of the cover - photo should show the melted component with some blackening to the circuit board.

Made a cable switch this afternoon, should prevent me from doing it again!

Hi Neil glad to have helped. Whilst the result was the same I think I should point out that Reversing the polarity even for a microsecond will cause a failure in the internal substrate that all Mosfets etc have. Basically they have a high resistance in one direction and low in the other. Control is via a low voltage applied to the substrate and if exceeded it either destroys (breaks) or fuses the substrate which is what I believe happened in your case as the Mosfet melted. So it may not have been the BEC that shorted but a MOSFET. Either way the result was the same.
Cheers
dave976

Neil,
I did a burn out with my fumble fingers some years ago. It was an expensive lesson for me.
Since then I am very careful about my initial wiring.
The worse thing that can happen is not being able to figure out what the problem was.
I feel your pain!
Barry

I agree with Dave. I might add checking voltages of your battery relative to the BEC that you are using.
BTY, you are not the first, if you did, to mix up battery polarities. Not something you do twice.☹️

Thanks dave, that makes sense. I suspect I may have fumbled connecting the battery to the ESC, as the battery I was using to test was a larger footprint than the one I usually use so was balanced on the battery box. Won’t make that mistake again. Have checked all wiring and no problems, the boat has been running fine and the batteries all get used without problems in other boats.

So assume that the wrong polarity even for a fraction of a second had an instantaneous impact on the ESC and blew the BEC and the first Rx - no smoke from the ESC with the first Rx. With the blown BEC I fried the second Rx and while thinking about the issue the BEC short caused the heating and smoke in the ESC.

That’ll teach me not to have a switch or fuse in the circuit.

Hi Neil, how unfortunate. Only you know how you connected everything up so it is difficult to reach a definitive answer. That said you have cooked the ESC. This is usually caused by wrong polarity but connecting the motor and battery to the wrong connections will also cause the same problem as will a direct short on the motor connections. Having cooked the ESC the BEC was also kaput and as a result your battery supplied 11+ volts to the Rx which for the IA6B only needs 4 - 8v.
I doubt if the jammed rudder would have caused the complete failure but would have caused heat in the Rx. I always check BEC outputs with a metre before applying to any Rx as I have suffered similar fates in the past. Many of my models are fitted with a separate UBEC as I find they give a more reliable power source than ESCs. I disconnect the red leads from the ESc's to the Rx.
Unfortunate that you damaged a second Rx but I doubt if you will repeat this in future.
Cheers
dave976

Have had a rather expensive afternoon.

I did a simple job in moving the water cooling outlet pipe from the side to the transom for the RTTL. Put a Y section in the pipe work to have twin outlets so disconnected the rudder linkage to gain access. Reconnected after fitting pipe work.

Thought I’d just make sure everything worked so grabbed a 5000 Mah 3S, connected the battery and the Rx stopped working. Checked it was paired, took Rx (Flysky i6) out of boat, put another battery on it, dead Rx.

So, tried another Rx.

Connected battery and the 60amp ESC decides to produce smoke, now have a dead ESC and the replacement Rx also burned out, sniffed both Rx and they both had a burned smell.

Did what I should have done when killing the first Rx and looked for any issues, found the rudder linkage was way too tight after I’d reconnected it and was causing the the rudder servo to chatter.

Checked the battery, found I’d picked up one with a low charge of 42%.

So, I freed off the rudder linkage and tested again, this time outside with a spare Shark ESC and another Rx, borrowed from my BYMS. All works.

Would a jammed rudder have caused an Rx to burn out? Would this have caused the issue with the ESC burning out? I use Deans connectors so no chance of reversing polarity into ESC.

Any opinions welcome!