First ride! (yayyy) Loop key problems! (noooo)

Finally took my board out for a test spin- worked like a charm! Everything seemed to be just fine, I spent about an hour just riding around the parking lot. Once or twice I thought I smelled burning plastic, but I couldn’t see any damage when I looked so I figured it was something other than my board. When I was done I tried to pull the loop key only to find it stuck, and my first attempts to remove it did nothing. Getting it home and carefully opening the enclosure and disconnecting the battery, I got a better look at the underside of the key:

That wouldn’t be a burned resistor would it? At the moment the key is still lodged in there, I think it must have fused with the melting plastic. There doesn’t appear to be any other damage, so I’m hoping I can just replace that part:

Could my wiring have anything to do with it? I’m using what I think is about 16awg, but it’s unmarked: I’m planning to do a full build log soon but I want to get this straightened out first. Thanks!

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The only time I’ve seen a loopkey/ antispark connector get hot is when it’s not fully seated. Is there a chance that the 3D printed cover is preventing it from being fully inserted?


Possibly… there’s a 1mm lip around the opening to prevent plug housing from coming out when I pull the key. I can’t tell without taking it apart if that was too much. If so I guess I’ll remove the lip and glue it down next time.

1mm doesn’t seem like enough to cause that, but it might. Glad you’re board is up and running. Hope the loop key is an easy fix for you.

Thanks! I wouldn’t have thought so either, but apparently not. It just goes to show that even the smallest details matter.

If I’m not mistaken the anti spark connector has a built in resistor, it sounds like this could be getting really hot because the connectors not seated correctly so all current is going through it.

Theres definitely a gap between the xt90 female and male. The resistor can be quite hot if there is no cable attached and would definitely be untouchable. I think the vibrations of your board makes those antiloop not perfectly inserted. If the resistor broke, you will always get the huge spark.

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Thanks, that’s good to know. So I think I’ve gotten lucky and not had any sparks, mainly because I couldn’t even disconnect it. I disconnected the battery from the loop key circuit and I’ll fix that before I hook everything back up again.

Small gaps between contacts create arcs and therefore heat and burning. I bet that was the issue

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yea, plastic probably melted together nicely, take an xacto knife and cut the connectors apart (batteries UNPLUGGED)


Is this 12awg wire or better? Cause this looks like speaker wire to me… you probably build a portable radiator

I think it’s 16awg, as it’s just slightly thinner than the vesc wires, and those are marked as being 14awg. You think I should go for 12? Thicker? The loop key itself is the only part that seems to have heated up.

Depends on voltage, but you say vesc so max 12S for that i would recommend 10awg wire, for 6S builds maybe even thicker.

Here’s another thought: the wire you ran through your XT90 might be too long. That creates extra resistance, and therefore more heat which will definitely melt on 16awg wire after a little while. Make the bridge as short as possible…

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You need high strand wire, that doesn’t look like it, I can’t really tell from the pics

You can clearly see in the picture that you didnt insert it properly. That is why the resistor fryed.

Okay, so with my battery being 10s (36v) is 12awg enough or should I go straight to 10awg? Definitely agree about keeping the wires short though.


I would say 12 is enough. 10 allows for a lot of headroom and is bulkier too. when I built my battery I used 10g for discharge and 12g for charging because I like headroom.

i honestly don’t think it was the wire. yes 16awg is too small. but I used long ass 16awg on my first loopkey without issues. the key wasn’t plugged all the way in, all current went through the resistor, resistor heated up, melted they connectors together

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