Charred bullet connectors on controller side

[medusa569]

After experiencing some "sputtering" or shuddering of my hub wheel I was double checking my connections for a loose one and I noticed that all of my 3 phase wires on the side near my controller are charred. The wires near the motor are fine. This may or may not be related to the hub sputtering. They are covered with plastic so some shortages aren't likely. Any idea of the cause???

 

[Beachcruzer]

Looks like you straight-up melted the insulation. What amperage are you pushing and what gauge are those phase wires? Were you riding harder/longer than usual? Maybe poorly crimped or soldered connectors creating resistance/heat?

 

[neptronix]

Too much resistance on those connectors.. you must be pushing some serious amps - or that connector has always been loose.

 

[Jeremy Harris]

This is a very common failure with those nasty bullet connectors. They have a pretty high resistance and don't tolerate more than a few amps before getting hot. They are just about OK for a standard low power ebike, say a 250W to 350W one (which is the power that the vast majority of Chinese made motors, controllers and wiring were originally designed for), but they can't take more than around 10A before they cook.

Replace them with something better, like Andersons or RC type bullet connectors and you'll probably not have any further problems. The bike will go better, too, as there's often an appreciable voltage drop across those cheap bullet connectors.

 

[amberwolf]

Almost any "bullet" connector or any other kind of pin connection that uses a thinwall "C"-shaped pin (split-tube) is prone to having the soft metals bend away from the split, leaving the connection loose, and much higher resistance than intended. The male pins get squished making them smaller, and the female pins get spread making them bigger, and nothing fits right.

 

[dogman dan]

Just to make it perfectly clear, perhaps to the lurkers out there, what happens is once a connection becomes loose, or just making partial contact, all the current has to flow trough less metal.

So it's like having a too thin wire, and it starts getting hot, melting the plastic covers and such. If the controller is high powered, then of course even more current is flowing though the weak spot in the wiriing.

It can happen to nearly any kind of connector, but the cheaper bullets and blade connectors tend to get the problem worse than larger bullets, andersons or other higher quality plugs.

Chances are, one of those connectors started resisting the flow enough to cause the motor to judder under load. Or lost contact completely.

 

[medusa569]

Thanks guys for your input and information. I'll change them out for other substantial bullets. FYI I am running 30 amps and a 500w motor with new size 12 flexible silicone wire. I suppose usually there must be failure at one end as the hub connectors showed very little heat residue. The charred ones were very much spread apart. Now I know what I was smelling every now and then. My question is this..with so much heat being generated then where in the future will the heat go to or affect since there is no fuses in line with the phase wires??
Am I looking at a then easier fried controller?
BTW apologies if my posting came across as a PM...I did not intend that.

 

[dogman dan]

Just upgrade to a better quality connector, and the heat in the connector will go away. shouldn't be any danger to your controller or motor, but if you melt off the insulation and short the phases, that can blow controllers.

 

[medusa569]

Thanks Dogman ! I was wondering if this silicone wire was an ill conceived choice. I'll just have to keep an eye on the wiring.

 

[parajared]

This happened to me too. I switched to 45a anderson power poles, and they were better, but still kinda suck because grit gets into the connection and causes the shorts again. I have had the best luck so far with the gargantous pa75 connectors, but those are probably too big for most people.

http://www.hobbyking.com/hobbyking/store/__15422__PA75_connectors_6pcs_bag_.html

 

[Ykick]

I stagger phase wire 4mm bullet connectors so that in the event insulation begins to melt there's less chance shorting between phase outputs of the controller.

 

[dogman dan]

That's a pretty good idea. Keeps the bundle slim as well.

 

[salty9]

Does anyone other than the manufacturers recommend using connection lubricant?