A friend of mine has a very strange problem with his electronics. I wont mention brand names, but they are all well known.

Configuration, 3 batteries used around 50 times, esc used around 10 times, brand new motor (same brand as esc)
On a training session, the (-) plug that is next to upper deck unsoldered during his run. That happened 3 times, 3 different batteries. After that esc doesn't turn on and he also broke chassis and upper deck as car went straight full speed

Next training configuration, same 3 batteries used around 53 times, another esc used around 30 times, around 30 times motor (set was taken by another car that was fully functional) (same brand as esc, same brand as previous set)
This time the (+) plug that is next to upper deck unsoldered during his run. Again esc now broken, won't turn on

Any idea what might be the problem? He is scared to try any configuration as he has already too many broken things!

The only constant is the batteries, servo, receiver. I don't think servo/receiver can cause such issue, batteries could but WHAT could that be and isn't strange that all three failed same time?!?!

You know that carbon fiber is conductive right? The plugs shouldn't be in contact with any CF part so the current is not diffused in the chassis... Now, electric arcs can make the plug hot enough to unsolder it, but the battery hole should also have melted in the process...

yes, and this was my initial thought. Nor the plugs are long enough to touch the chassis nor the plugs touch the upperdeck. Especially, the later set had a plastic case on the plugs!

I'm only thinking that the batteries (as the only suspect or lack of any other?!) have an issue internally on both the internal female slots that might cause the arcing and hence the extreme heat, BUT all three batteries??? If this is the case, way too bad quality

If this is the case, is there any warranty?

id like to know exact setup pinion spur battery C rates and mah.. I can guess that the esc is pulling more amps than batteries can supply.. unless some1 has soldering issues.

110c 7.6v 6000mAh
116/30 ratio = 7.19 (it's normal ratio for our track 7.2-7.4 most people run)

Second set has been soldered and used for months! we just took it from one car and just put it on the other, no soldering in the process.

Oh you have no idea how much I wanted this ( bad soldering) to be the case as I would make fun of my friend for ever

Unsoldere wires sounds like too much current.

Too much timing or is there something with the motor (did you try a different one?)

timing is the default on the motor. on the esc he has less than me!

yes of course, he has tried 2 different sets. now both escs are broken! don't turn on! we are very scared on what to try next, as there are already 2 escs broken!

Check for seized bearings or parts in the driveline, if something is really jammed it might be causing the plugs to come unsoldered by drawing lots of current to make the car move.

Also, double check the ESC and the motor for any solder bridges joining the different terminals.

Check the motor for any solder/washers/rocks that could have fallen inside the can or been pulled in by the magnets.

Make sure the plugs and wires are soldered on properly. Once they've cooled down, try holding the wire and pulling hard on the plug. If it comes off, it wasn't soldered on properly to begin with.

we can all just guess. without seeing rc in use and knowing how rc cools down between batts .I have no real fixes.

Look closely at your wire connections. Bad solder joints on one end can cause heat issue on the other end.
And check your plugs. I had a worn bullet plug going into a battery. Wire came unsoldered a couple of time, I kept resoldering until i discovered that the loose buller plug into the battery was the culprit.

The problem occurred twice!
On first time I thought that the soldering was the case as he isn't very good at that, yet.

BUT on second time I took a COMPLETE set that was working on another car and put it on his. There was no soldering involved on that process, that system run perfectly for many batteries!

So, soldering isn't the issue

So the only common electronic piece common between both set ups is the servo? Try a new servo. I had a bad servo that worked intermittently that gave me issues like a bad esc. Could be your issue too.

Servo and receiver are the only things common yes. Could the servo cause such an issue??

Well I've never seen a bad servo cause an unsoldered joint. Usually it's caused by an old or worn battery plug(like a deans with a worn spring) which doesn't seem to be your issue, if I read correctly(I'm assuming new battery wires/connector on new esc). I've seen electronic/electrical issues where the issue of one is caused by the other, even when it's not logical.