How-To: Anti-Spark XT-90S Loop Key

May I have not on/off switch but only this anti-spark loop key and f.ex setup my vesc, ride and so on?

Thanks for answers!

yes you can use this loop key instead of a switch, i use it on 2 boards

1 Like

I killed it, but it was user error. Vaporized one of the bullet connectors. :exploding_head: I plugged it in while i was parallel charging. :flushed::face_with_symbols_over_mouth::sob:

It was not that hard to replace as the glue was sort of rubbery. It was tricky to glue in the new one though, trying to keep the glue from getting into the wrong spots.

I think people who kill the resistor early are not pushing them 100% all the way in before riding. I always made sure of that.


I can confirm this, happened to me my first time out. The plug wasn’t fully secured so it slid a bit as I was plugging in. Make sure to brace or secure your plugs, a glue gun works great for this.

Just to clarify, is it ok to leave the BMS plugged in at all times, even if you don’t have an on/off switch on the BMS? So the loop key would be in between the VESC and everything else, on the positive wire.













What size cable braid is that boss?

I´m not the boss, but i can say it´s three layers of 0.25" tinned copper braid :wink:


Thanks boss #2! Is there a specific length you shoot for to achieve a specific fuse rating? @b264, @Andy87, or anyone else knowledgeable on the topic?


Just choose diameter according to the fusing current you want.




If I wanted it to fuse, I would solder an actual fuse to it. I made that specific one rated for 135A+ continuous because I don’t want it fusing. Ever.

I’ve thought a lot about this, and everyone differs, but me personally, if the board starts severely malfunctioning while I’m at-speed in heavy traffic, I would prefer the battery stay connected as long as possible so I still might have brakes to stop while the board is burning-down. If you’d prefer the loop key fuse-out to possibly save your expensive electronics instead, that’s personal preference but I’d rather have the extra couple seconds of throttle response myself. Once it fuses, you’ve got no brakes.

Basically it’s ME > BOARD or BOARD > ME

I prefer to give the benefit of the doubt to myself over the safety of the board/battery itself.


Thank you for the confirmation

1 Like

Dumb question, but how did you urethane it so well?

About 30 coats heh heh heh. No, I’m not exaggerating.

I mean like, did you dip it, or brush it on.

My initial thoughts would be to dip out of a larger can, your bottle just seemed like it didn’t have a large enough opening to dip it in though.

The other angle is, if something goes wrong in storage or charging, the fuse might save your house, family, and multi-unit domicile co-inhabitants. :slight_smile:

1 Like

That’s why I fuse the charging :wink:

For wires and loopkeys and things needing physical abrasion resistance I use

MG Chemicals Urethane Conformal Coating in the 55ml brush-on bottle

But for PCB waterproofing I prefer

MG Chemicals Silicone Mofified Conformal Coating in the 55ml brush-on bottle

except on heatsinks, then

MG Chemicals Acrylic Conformal Coating in the 55ml brush-on bottle (because it’s super-thin)

1 Like

You just put a fuse of a rating slightly higher than your charge rating on your positive charge line?