BMC Motor Burnout!

[Jonathan]

I finally got the extended battery back to my bike mounted properly. I decided to make a run to the local hill to test out the performance of the batteries.
About 6 miles into my trip up a 1500' ascend the motor cuts out. No pop, no nothing. I still got power to the controller but no throttle response what so ever.

I went through fechter controller diagnostics with the following results.

1. Power to the controller with LED lit. CA registered 33V
2. Voltage regulator works, +14VDC & +5VDC & CA is active
3. Throttle works. Sense goes from 0-4.2V
4. FETs check are all open between GND & phase while I get a -3.8M Ohms between (+) & phase
5. gate vs drain diode check ... 0.3V seems good.

I then proceeded to check the motor side. Hall sensor looks good at ~700 Ohms vs GND. GND & +12 and all the phase wires were shorted together? HUH!

Opened up the BMC motor and look what I found.

A bunch got welded together.

The culprit ... one of the phase wire with insulation completely vaporized! ... Yes Completely Vaporize!

The funny thing is I was running with 36V battery pack & 35A controller with the Cycle Analyst current limit of 25A.

So you guys with BMC expecting to run > 1000W I would highly recommended that you review your wires, especially if you're going to just shorten the stock.

The good thing through this entire ordeal is I got an intimate look in my motor & controller. Not so mystique as it used to be.

Thanks fechter & Doug for helping me through the troubleshooting process. Hopefully my controller is OK and a quick rewire (beef up to 14 or 16 AWG) would get me back on the mountain.

 

[RLT]

Well, crud. Sorry to hear it.

I had to beef up my BD36 wires too (to 12Ga silicone). You'd think they would install something heavier than 16 ga at the factory.

 

[safe]

I've got a small motor that I'm going to trick out with overvoltage and was wondering about the small wires they were using. I guess I'll go ahead and do the upgrade before I even assemble the bike.

Good information...

 

[solarbbq2003]

were did the motor come from? ( ebikes.ca, evtech, teamhybrid, superkids, a few places in australia supplying bmc also the 250w ( alias 350watt version)
)was it 500watt version?

 

[dirty_d]

looks like war

 

[fechter]

Guess it needed those upgraded wires like Maytag and others have done.

Nice 4th of July display. Thanks for the great pics.

 

[A1234LIFE]

Same thing happened to me on Friday. Worked on the bench and then went bad in the first hundred yards of test ride. I replaced the wires on the motor and it is working fine now.

Steve

 

[knoxie]

Hi

The wires will heat but i ran 48V 35A on one for 2 years with no problems, I have seen the joints inside go though, they are often poorly soldered and can/will melt the solder if pushed over 1 KW or so, the thing to watch also is your magnets! High power for long runs can sometimes melt the adhesive and cause the magnets to spin in the rotor!! so fit a temp stat in there.

Knoxie

 

[A1234LIFE]

Anyone have the definitive, "How to hook up a Clyte Analog Controller to the BMC motor". I used the pinout from Doug which is:

Phase Wires:

Controller Motor
Yellow Blue
Blue Green
Green Yellow

Hall Wires:

Controller Motor
Red Red
Black Black
Yellow Green
Blue Yellow
Green Blue

It does run this way but it just doesn't seem to have much power.

 

[Joey]

Hey A1234LIFE,

I believe you have the motor to controller phase wires wrong. See the attached photo obtained from another E-S thread.

-- Joey

 

[A1234LIFE]

I saw that diagram and can't remember if I tried that or not.

Jonathan,

Would you let me know if you have an analog or digital Clyte controller. Also, did you wire it the same way I have listed. I ran mine at 36V with a hard limit of 25A and it seemed fine until about mile 5 and that was it. Same problem you describe except I had already rewired mine with heavier gauge wire from the first problem with the included controller. It looks like it cooked the motor this time. I think the windings are done.

Steve

 

[Joey]

I would like to upgrade the phase wires on my EVTECH BMC rear hub motor. I previously shortened the original wires and replaced the connectors with Anderson Powerpoles and mini-XLR connector for compatibility with a 24-72V 35A Crystalyte analog controller from ebikes.ca. I think I toasted the existing motor phase wires during a recent stress test when I was trying to observe voltage sag of a 2s3p Milwaukee pack near end of discharge by repeatedly climbing a steep hill after a lengthy speed run on flat ground.

I'm trying to determine whether I should attempt the upgrade myself or pay someone else to do it. I suppose the choice to have someone else do it depends on their experience, the cost including shipping, and estimated turn around time. Is there someone willing to do this conversion for a fee? I'm in Albuquerque, so a Southwestern or Western US "repair" location is preferred.

If I have to do it myself, I am in need of detailed step-by-step instructions for disassembling an EVTECH BMC rear hub motor and rewiring it with lower-gauge phase wires. There are a number of people on this site that have made this conversion but I am having trouble finding a concise description of how to do it. Close-up photos of the disassembly steps would also be very helpful. I'm particularly unsure about the mechanics of disassembly. I haven't bought any wire yet but am leaning toward mil grade 14 gauge teflon coated stranded wire for the phases. I'm not sure what gauge the hall wires should be and where to purchase them. I'm also not sure what sort of insulating sleeve to use for the wire bundle. Standard heat shrink seems too fragile for this. If someone has some extra wire (phase and hall) and insulating sleeve from a similar conversion I would consider buying it from them.

-- Joey

 

[knoxie]

Hi

Bad luck on that!! check this thread out it should detail all you need to know, its not really that hard to do it.

http://endless-sphere.com/forums/viewtopic.php?f=6&t=4189&st=0&sk=t&sd=a&hilit=kmx&start=15

Cheers

Knoxie

 

[Joey]

Hi knoxie,

The link you gave me for rewiring an EVTECH hub motor shows the wiring steps but starts with an opened up motor. How do I get the motor open? Does the sprocket assembly have to come off first? What is holding it on?

-- Joey

 

[Jonathan]

After rewiring my motor still doesn't work. I think the winding is fried. I might have to do a rewind.

As for the wire upgrade, to open it's fairly easy.
Just unscrew the dozen or so philips screws on the freewheel side. This will expose your wiring.

To swap out the wiring is however a PITA. 16 AWG is pretty much the largest you can get in their w/o modification. The biggest problem is doing the 90* bend. I plan to machined out the short opening a tad bit on the next unit to ease the snaking process.

After this burnout I plan to use 14 AWG high stranded cable. Remove the silicon insulation and replace it with heat shrink. The idea is to keep the wire cool enough so I don't have to worry about the heat buildup.

Now as for the color code, mine's a little different than Maytag. I think they changed out their wiring since last year.

Clyte Controller ... BMC Motor Hall
Red ... Orange
Black ... Black
Yellow ... Yellow
Blue ... Blue
Green ... Green

Clyte Controller ... BMC Motor Phase
Yellow ... Green
Green ... Yellow
Blue ... Blue

It's not a big deal regarding the phase colors combo since there's only six different combination. Just use < 36V & low throttle when you test.

 

[Joey]

Hey Jonathan,

I assume that I need to remove the sprocket assembly from the axle before the cover can come off. How do I get the sprocket assembly off?

-- Joey

 

[Jonathan]

You need to remove the wheel/motor from the bike.
The freewheel does not need to be remove.

You'll see the screws when you remove the wheel :lol: trust me.