Controller heat and wires/connectors melting

[ebike11]

Hi guys
Im having a problem with my KU93 controller. The shunt is modified to 25-28A or so for more torque.
I have a lower coded ,high rpm Bafang 8fun geared rear motor and battery is about 59V or so after a full charge.
At first I was melting the butt connectors from the heat but even with different connectors, the heat is still melting the wire coating and onto other smaller wires as well.
Would any of you have a heat solution that worked well for you ?

Thanks!!!

 

[DAND214]

more information would help.
Wheel size, wieght, hills no hills. Did it melt prior to the mod?

do you have the correct ccolor ombo or is this a self learn controller?

Do you know the no load amp draw?

No binding in the wheel?
Anyone else got ideas?

Dan

 

[ebike11]

Pretty sure the blue yellow and green match up correctly on the bmsbattery KU93
The bike runs well and smoothly.
Bike is a regular 26" MTB

On long straight flats, how long do most of you keep your throttle wide open or 3/4??

Thanks

 

[Gregory]

I bet most people run WOT all the time.

What type of connector and gauge of wire do you have?

 

[ebike11]

The Ku93 controller wires look to be 12guage and are short.
As you may or may not know, the wires coming from the Bafang 8fun motors are very thin, but they are melting/burning even on the wires coating themselves. Its difficult to seperate all the wires from contacting each other because on the KU93 there are a lot of wires coming out from it.

 

[ebike11]

Any more ideas??? Anyone have problems with Bafang 8fun wires??
They are really thin!!

 

[dogman dan]

I have seen some pretty thin wires on controllers. It's possible you have upgraded your shunt enough to start heating the wires some. Previous heat could have toasted the wire itself some.

For sure, with the shunt mod and the fast motor, you pull massive amp spikes.

 

[d8veh]

You should solder the phase wires at the controller. It's just as quick to cut them if ever you need to disconnect them. I suspect that the heat is travelling down the wire from the connector. Those bullet connectors are OK up to about 22 amps. After that they overheat.

You also need to check the large traces inside the controller. They often don't reinforce them in the KU93. They'll blow if you go over 25 amps. If they're flat, reinforce them with some wire and lots off solder. like this one:

http://www.linushelgesson.se/wp-content/uploads/2011/12/power_traces.jpg

 

[Gregory]

You didn't mention the connectors.

If the wires are heating up near the connectors I'd be more inclined to view them as a high resistance point than the wires. If not then fatter wires will have lower resistance and sink more heat.

 

[ebike11]

Yeah mainly near the connectors. I might just solder them together and see what happens. I even put an xt60 on two of the phase wires and the heat even lossened up the solder. Perhaps it wasnt soldered correctly

As for the shunt, i soldered two small pieces of wire on the shunt and can trim the wire if I want higher Amps. The pieces of wires are about an inch and a quarter long

 

[Lebowski]

no load current at high rpm ?

 

[ebike11]

no load current at high rpm ?

Sorry how can I test that???

 

[Lebowski]

no load current at high rpm ?

Sorry how can I test that???

you put your bike upside down with the wheel in the air and give full throttle so it spins at max speed. Measure the the current from the battery.
It is an indication for whether the halls are connected correctly and how good the timing (hall placement) is.

 

[friendly1uk]

The shunt is modified to 25-28A or so

Thanks!!!

Do you actually know, or are you just messing about?

 

[ebike11]

Oh there are no halls...only phase wires from the Bafang 8fun

My friend soldered the wires and the max. On the Turnigy, the highest I seen with wide open throttle was 28A
I didnt want to trim the wires to go over 30A

 

[dnmun]

since there is no picture of what wires you meant i will assume you are talking about the phase wires to the motor and they are overheating at the connector and the insulating sleeve is melting?

you should cut off the connectors, slide heat shrink tubing over one end of the wire and then twist them together colinear and solder the connection, then slip the heat shrink over the joint and shrink it.

i always wrap a joint with black electrical tape at least one turn before i put the heat shrink over the joint and shrink it. that makes the tape stay in place and adds to the protection from a piece of the wire strand from puncturing the side of the heat shrink tubing.

 

[DAND214]

Oh there are no halls...only phase wires from the Bafang 8fun

My friend soldered the wires and the max. On the Turnigy, the highest I seen with wide open throttle was 28A
I didnt want to trim the wires to go over 30A

Is that 25amps at full speed or from a start? If from a start did it drop down to what?

A no load test is done with the wheel in the air and the throttle WOT, then you read the meter to see what it says at NO LOAD.

Dan

 

[ebike11]

since there is no picture of what wires you meant i will assume you are talking about the phase wires to the motor and they are overheating at the connector and the insulating sleeve is melting?

you should cut off the connectors, slide heat shrink tubing over one end of the wire and then twist them together colinear and solder the connection, then slip the heat shrink over the joint and shrink it.

i always wrap a joint with black electrical tape at least one turn before i put the heat shrink over the joint and shrink it. that makes the tape stay in place and adds to the protection from a piece of the wire strand from puncturing the side of the heat shrink tubing.

Yes they are the phase wires overheating at the connectors and sometimes the insulating sleeve is melting in certain spots.

Should i put shrink tube on the entire length of wire?? I had some wires melting onto others as well
Thanks!

 

[dnmun]

if the wires have melted where they pass through the axle into the motor then they may be shorted or will short inside the axle yet. so you should consider rewiring the motor to increase the size of the conductors going into the motor through the axle.

i can imagine your phase wires are the little 18AWG or so wires so it is almost impossible for them to carry the increased phase currents you are now pushing without overheating.

but the connection you have now in those little connectors produces the most heat so if you can get by with just soldering the connection to get the resistance down inside that connection, it may not produce enuff heat to melt the wire insulation on the wires next to it.

so you might try that first and see how it turns out.

 

[dogman dan]

I was assuming it was the wires from battery to controller.

Cut your phase wires 6-8 inches from the axle, and attach, with robust connectors or solder, much much thicker wire. At least 12g. This will carry current better, and it will also heatsink a bit of that heat out of your axle.

It's a pretty standard modification, that should have been done when you did the higher amps.

Now go have fun melting that motor.

 

[ebike11]

Ok dogman......
Well i stripped the insulation off of the phase wires and blue wire only looks like a copperish/ corroded color to it where the yellow and green are just fine, shiny silver.
Was it the heat that turned the wire color?? Or something else?

Thanks

 

[d8veh]

Take things one stage at a time. Cut the connectors off the phase wires at the controller. Then solder and insulate them. See if that solves your problem before doing anything drastic. It probably will.

 

[spinningmagnets]

I doubled the stock Bafang BPM wires inside the axle, and it was fairly easy (Tutorial in the thread-link below). For the wires on the outside of the axle, do as dogman suggested and use the fattest wire you have laying around, 12-Ga at a minimum. Since you seem to like pushing the envelope, perhaps add a $2 temp sensor while the motor is open? Even if you don't add a readout for a while, the sensor is cheap and easy to glue onto the stator.

Bafang BPM teardown and pics
http://endless-sphere.com/forums/viewtopic.php?f=16&t=51237

 

[ebike11]

Thanks so much guys!!!
@d8veh, I did as you mentioned but no signal, motor didnt respond uggggghhh,
so thats why i stripped the wires a bit to look for a possible problem. Thats when I noticed the blue wire
heated so much its notw a copperish/brown instead of silver.
I think it was from the heat
Thx spinningmagnets for the link!!! I may need it

 

[ebike11]

Hmmm i think wires inside the motor might be shorted or something. There is no signal when I connected my controller and battery but i put the controller on another motor and it works so i think its not the controller.

Is there a common area to look around the 8fun wiring that I should check?? Should I open up the side motor cover to access the wires??

Thanks!