BMC 50A controller & 1000W V3 motor

[oatnet]

While this negates my previous joy, it reiterates that the factory phase wires are too small on the BMC motor. Even at 1000W continuous, we'll pull 87.6 A per phase. As a reference, a sufficiently long copper 10 Gauge wire has a continuous rated ampacity of 55A; the factory wire is rated somewhere around 28A. That's a 1.59 times overcurrent with 10 gauge and 3.12 times overcurrent with the stock wire.

What is the continious load for 8gauge in the run you are trying to achieve, minus 6"? What is the continious load for 6" of the factory wire soldered to the 8ga? Just curious if my solution would meet the requirements of your test.

-JD

 

[TylerDurden]

That has definitely been my experience with ebike controllers. However, when choosing Kelly DC controllers, I was suprised to find that they are rated motor-side. When sizing contactors for my Bus battery pack, Steve from Kelly said that the draw by my 500a controller would never get up to 400a. The 400a silicon fuses on the pack have never blown, so I figure that is accurate. At some point I took it as a given the DC controllers were all rated motor-side, am I confused, was that just a marketing technique?-JD

I wasn't sure myself...
From Ev digest:

• > FWIW the 600 amp rating on motor controllers is motor
  > current, not battery current.

While this is approximately true for Curtis controllers, it is not true
for DCP, Auburn, and EVCL controllers. These controllers are spec'ed
for battery current and can deliver substantially more current into the
motor, at least for brief periods.

The "600A" controller in question is almost certainly a DCP600 Raptor
since I recall Damon once posting that it had a peak motor loop current
of about 3x its nameplate battery current rating.


For 'mudder' and others, I was referring to "current multiplication" that occurs when controller duty-cycle is less than 100%. i.e.: at 50% duty cycle, motor current will be 2X battery current.

 

[liveforphysics]

You read my mind Tyler.


Mudder- If you're going to be seeing battery current limited to 50amps, your phase wires to the motor will be seeing as high as 150-200amps under conditions where the controller is current limiting with PWM%, or partial throttle situations.

It works just like a current boosted bucking power supply. Pin must equal Pout (minus a few percent for controller heating).

An example: Take 50v in at 50amp, if the PWM happens to be at 50%, the V-out bucked to the phase wires is 25v (the motor windings are an inductor of course), and to make the power equation balance, the current is 100amps.

 

[full-throttle]

Copper is the ideal conductor

except for silver

This is a big no-no in PCB land because vias (the holes in the PCB) do not take tensile forces well and tend to crack if you strain them.

those 5 wires do not exert force strong enough on the PCB to crack the vias and certainly the force in not tensile, besides the vias are likely to be filled with solder

how exactly the cassette would transmit any torque to the hub?

 

[Mudder]

What is the continious load for 8gauge in the run you are trying to achieve, minus 6"? What is the continious load for 6" of the factory wire soldered to the 8ga? Just curious if my solution would meet the requirements of your test.

-JD

The continuous load for 8 gauge would be 73 amps. Note that I'm talking about the wire that runs through the axle; I've replaced the stock wire with 10 gauge enamel coated wire. I've got beefy wire once we get out of the motor all the way to the controller.

 

[Mudder]

Copper is the ideal conductor

except for silver

Ha, you got me there . The price difference is enough to keep me from going with silver .

 

[Mudder]

how exactly the cassette would transmit any torque to the hub?

As someone originally suggested (and I countered , I guess we'd have to break the wires out on the disk side. Or just not use the cassette .

 

[ebikes-sf]

Great ideas and testing info!
However, the weakest link of the motor remains freewheel/clutch assembly. 30-33A is maximum it can handle at low speeds (under ~ 7mph). Going over 35A, especially up steeper hills, will eventually result in bent axles on green gears or stripped one way bearing.

 

[nicobie]

I still have one spare sprag bearing assembly for my 600W-S. If I blow that one I'm just going to weld it together and put up with not having a free wheel.

 

[bkwilless]

I had the same problem with spokes breaking. It was not the wheel builders fault. It was the fact that I weigh 290 lbs. I replaced them three times with better spokes and nipples that allow a greater angel, etc. Then I had the stupid thing build with a one lace pattern for kicks. I have put three times the mileage for when it would break with the three lace problem and absolutely no signs that there is any problem.

Thanks mudder for all the photos. I busted my wire at the axle and need to replace them. Those photos are priceless since I am not a savvy engineer.

 

[ebikes-sf]

Finally got error codes from BMC (red LED on controller PCB):

1. Continuously ON: Everything is normal
2. To glitter twice: Braking issue
3. To glitter three times: open circuit or wrong component value between Sense Resistor and LM358
4. To glitter four times: issue of mosfets at low circuit
5. To glitter five times: issue of mosfets at high circuit
6. To glitter six times: issues of 60/120 degrees or motor HS sequence
7. To glitter seven times: over current, too long Sense Resistor Wire, too low setting voltage for short circuit protection
8. To glitter eight times: low supply voltage
9. To glitter two times more quickly: Throttle is not released or over voltage of output of throttle
10. To glitter three times more quickly: lock rotor protection on ( motor is locked )
11.To glitter four times more quickly: disconnection of phase wires
12. To glitter five times more quickly: over temperature protection on

When issues occur, LED will glitter for some times as indicated above and glitter again at regular intervals.

 

[fechter]

Good work on getting the codes! Very helpful.

I did some measurements with my BMC scooter (non-hub) motor a while back. I was seeing up to 3.5x the battery current on the motor phase wires during heavy load/partial throttle. When the duty cycle of the controller drops below a certain point the output becomes discontinuous, so the 'multiplication factor' no longer follows the duty cycle at very low settings.

 

[Chuleo]

Sorry for digging out an old thread but I've got the same problem with my BMC 50A controller as the guy in the post before.
The led blinks once then two seconds pause and over again. Does someone know a solution to this problem?

Everything is connected correctly (it used to work that way). I was did a short test ride (max 3 miles) when the motor began to make weird noises like it was out of synchronization. I then shut down everything.. The next day I tried some differet setups (slow/high speed, 30A max/40A max, soft start/normal start) and it was working again. Now on the third day nothing works. If I move the throttle the motor just makes a clicking noise and spins about 90° then stops. The whole setup is brand new (20AH Ping, V4C motor, BMC 50A controller). Every wire is where it should be..

 

[fechter]

I would suspect a bad hall sensor or connection to the hall sensors. Check the connections first. Make sure the pins are fully inserted in the body.

You can test the hall sensors by using a voltmeter and turning the wheel slowly backward. With the controller on, but no throttle, you can measure the voltage on each hall signal wire. You should see each one alternate 5v on/off as you slowly turn the wheel. Best to measure at the controller to test all the connections between.

You could also have a bad connection on a phase wire or some kind of failure in the controller.

I wish we knew what the blinking codes for the LED are.

 

[mr.electric]

I found a loose pin in the hall sensor plug but that was not the issue. I was so frustrated with my bmc failure 3 days into a new set up that I switched to using 9c. I have several Ebikes , sold my bmc motors. I think the controller was bad on mine.