Can you help me figure out why I fried 2 times in a row my XT90S loop key ?
My battery is a 14s3p Samsung 30Q, the loop key is on the positive terminal of the battery.
I fried my loop key (big spark when connecting it, black residue, and now I measure a resistance way higher than 5.6Ω). I made another one, after 1 or 2 connections, it fried again.
Any idea why ?
I burnt one by not having the loop key all the way in during a quick test. Smelled it and pulled it out. Next time installed it went pop.
Not pushing the key all the way in.
Check the polarity of the XT90 connectors on the battery
@b264 well it wasn’t pushed all the way in, but it sparked before letting me a chance to do so 
@Linny I checked with a multimeter, the polarity is ok
It’s permanently broken because it was operated without being pushed in all the way.
Make a new key. You used the female side for the key, right? (male side on board)
The female side is the one that’s broken.
In the future, make sure you fully insert it, don’t just plug it partially in.
Yes I use the female connector for the key.
I’m pretty sure I pushed it all the way in since I knew it could damage the connector if I didn’t.
I’ve made a new loop key which fried too, so I’m trying to figure out what’s going on before killing more connectors 
It would be interesting if you could make a loop key with a tiny buzzer that would go off until it was fully inserted.
The only thing that will kill them is being operated while not plugged in all the way.
and using them for 20S voltages (84V)
AS150 is another option. I used one for quite a while on a board until I popped in an Antispark.
Is it possible that the black residue on the male connector because of the first spark, prevent the connection with the resistor on the female connector ?
How long does it take to kill while partially connected ? Maybe I plugged it too slow, I really don’t know 
It don’t take long… milli-seconds… your entire battery power will be flowing through that tiny resistor…
milli-seconds
Yeah generally the ESC filter capacitors charge in a couple milliseconds. You don’t want to apply throttle to the system without the key plugged in all the way. Not for any amount of time, not even for less than a second. The 5.6 ohm resistor inside the key would become part of the circuit and start dissipating huge amounts of power (more than the motors themselves) and get super-hot and fail in a very small amount of time.
Send a photo of the pin if possible. It’s likely to be okay
At least wipe the soot off it if you can, preferably with isopropanol, if you are even able to obtain isopropanol.
I have a problem. My loopkey sometimes sparks. Not always, like 1 time out of 5 tries… And the resistor is not burnt up because I can still measure the 5.6ohm resistance… Any clue on what’s going on?
Can you show us a high-res photo of it from this angle
and also a high-res photo of the male side you plug this into. I have a suspicion the pins on the male end are slightly compressed and may need to be spread out a tiny, tiny bit.
These are the highest res I can upload directly here (they got backscaled to 666x500, but I think it doesn’t look too bad) if you want I can also upload them to my drive in higher resolution
@Dinnye Are you able to measure the resistance between the socket and the ring? (with a multimeter)
My multimeter probes aren’t long enough to measure that way, but I can measure the resistance between the ring and the other socket.
Btw, 20ish more times plugging it in, today, it only happen once… seems like it’s a rare occurence.
