Melting loop key? SOLVED

Magic smoke came from my new xt90 anti spark loop key.

This is my first time using this so I prob did it wrong lol I plugged it in and my motors were moving very slow and then the male “key” with the resistor started smoking.

What did I do wrong Do I have to have the live wire at a particular end of this ? Or can it go on either end

It might be a similar problem to @whitepony Something about the loop wire being to big.

I missed that thread let me look for it

It’s on ES somewhere. On one of his build threads I think.

This is what he said:

about the loop key: I know quite well why my loop exploded and yours worked: my loop was too large! most of you directly bridge the 2 soldering joints of the XT90s plug and then attached something to pull the plug out again. I thought I just use a cable and wind it in a slightly larger loop, so that I can use it to pull the plug out at the same time. the problem is, that the inductance of a single wire loop is increasing with loopsize (~ radius*log(radius)), so the inductance of my loop key was much larger than that of most others.

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Oh no way! So I have to do a direct bridge and it will work?

Do you know if it matters to which side the live wire is?

I don’t think it matters. Yeah, direct bridge. @whitepony probably knows more about it than me.

Gonna try it right now made a new key

Tell me how it goes.

Didn’t work melted again lol I tried a new one

I cut the red wire from the old loop key since its toast. I need to order more now hahah

What about trying the power from the batteries on the other side? Is there a resistor on one side?

This problem only happens with the XT90S. Could it be something to do with the resistor?

It might be that I need to put the power on the other side but I have no more to test it out. They cost 12 dollars for a pair lol I’ll have to order more.

I went ahead and made me a temp regular xt90 key so I can use the board it works fine

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Could it also be that you are doing it on the positive side maybe?

Shouldnt really matter what side… i have a sneaking suspicion that these XT90s are not up to task. They use only very small smd resistors. I don’t think high voltage e skateboards were in mind when they were designed. I have no proof of this… just a theory.

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only reason i got them is because ive seen them in a lot of builds I thought they worked pretty well lol.

@GhettoFab.rictation I installed one of these in your series connector so let me know if it works or not!

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I had wire about that long on my loop key, and everything worked fine-

I think it’s what @lowGuido said, that the xt90’s simply can’t handle it.

Hey. This XT90 work good with 12S, never had any issues with it when directly bridged:

In my Drift Trike with 20S they are reaching there limits :joy:


Does it have to be connected in a certain way? In terms of the live wire? Maybe live wire to positive? Not sure what I put it on tbh

ok, if i remember correctly it is not a resistor in there, it is a capacitor. resistors dont care about polarity, capacitors do.

swap the wires going into the plug on the board side and you should be good.