John in CR wrote:From my understanding people have had trouble over the years matching BMC motors with controllers. It's been speculated that the issue is one of advanced timing placement of the hall sensors. You've called it a powerpack motor, but what motor is it exactly, because I see some different MAC motors at EVdeals? You should contact EVdeals, which seems to know some stuff since he mods motors, and maybe the manufacturer too. Hopefully the motor is neutrally timed, so the normal ebike controllers will work with it, since I don't think you're getting beyond the electrical rpms these controllers can handle. If the motors have some kind of advanced time in the halls, then I'm sorry to say but you may need Burtie's timing adjustment board to get the motor running optimally, or it could require a proprietary controller from the manufacturer.
Thanks for your detailed posting.
I get these "BMC"'/Powerpack motors as discards from a local bike shop that has a service arrangement with another shop that rents out ebikes with Currie/US Pro Drive/Synergy/etc. drive systems. The rental bikes are frequently abused, so there is a steady stream of burned-out controllers where the motor is in fine shape and only the controller is fried. These motors have a built-in controller that I remove and convert to a standalone motor. It is my understanding that the "600w" version of these BMC motors uses the same motor core as the Powerpack motor (Tim O'Brien's trade name). I have also played around with the smaller "300w" BMC motor that is identical to the "600w" motor in form factor and faceplate mounting but is half the height and on each tooth uses 15 turns of thinner wire instead of the 9 turns of thicker wire on the "600w" motor.
After cleaning out the non-working internal controller, I install my own Hall sensors positioned on the stator to give minimum current draw when the motor is spinning under no load at maximum throttle, or about 2 Amps at 24 volts supply. Most of my motors are set up for CW spinning and for the Infineon family of controllers. One of my motors is set up with two sets of Halls, one for the Infineon, the other for the Headline controller that I was also using with a Headline/Cyclone motor for a while.
You can see all of this in the photos at the links below.
Photos of "600w" BMC motor:http://mrbill.homeip.net/albums/mac_bmc ... index.html
Photos of "300w" BMC motor:http://mrbill.homeip.net/albums/mac_bmc ... index.html
You might notice that I position my Hall sensors slightly offset from the stock Hall sensors that are found in the slots between the stator teeth. The stock Hall sensor position did not result in the most efficient operation with either Headline or Infineon controllers and may be one reason why people have a hard time running this motor well. I recommend running your own Halls if you really want to tune it up.
John in CR wrote:I'm confused as to why you modded the shunt. Were you trying to get beyond the program settings available? Typically shunt modification is only done when you don't have a programmable controller, or if you need to fool the controller about how much current is allowed like I've done to increase regen braking force.
I believe that the BMC motor presents a tougher peak load than most motors, requiring higher peak current under partial-throttle, high-load conditions. I was not able to achieve smooth operation with the Infineon controller with these motors at partial-throttle, moderate/high load with system voltages higher than 24 volts nominal with the stock shunt on a 12-FET (EB312 board) controller without physically modifying the on-board shunt by decreasing its resistance.
The controller clearly has some hardware peak current limit that depends only on the resistance of the shunt not on its programming, and believe me, I tried modifying all of the programming parameters (Block Time, Phase Current limit, overall limit). Only by reducing phase current limit significantly was I able to reduce or eliminate the rough running, but it also made the motor quite gut-less when running at partial throttle. It would bog down very quickly at partial throttle.
After making this hardware modification it was then necessary to adjust the programmed current limits proportionally so that the original desired current limits were retained.
I made these changes to the shunt with Lyen's blessing--he had already added a third shunt wire to the board--after he consulted with his source for these controllers.
John in CR wrote:I'm also confused by your statements about a CA measuring the new shunt resistance, because a CA can't measure shunt resistance. In fact, unless you have the CA model with it's own shunt, you have to set the shunt resistance of the controller in the CA for it to give valid data about current. If you mean that you recalibrated the CA after you modified the shunt then all is good. Note that if you calibrate the CA by measuring actual no-load current from the battery and adjust the shunt resistance input until the CA reports the same as measured current, then to get it exact you have to account for the small current used to power the controller, which is a fixed amount, not variable like what runs through the shunt.
I have a power supply that into a dummy resistive load can supply a constant current, say 8 Amps. (It takes a minute or two for the large power resistors to settle down to a constant temperature before the current is stable.) I can measure this current with relatively high accuracy with an in-line DVM (not a clamp meter) set to measure DC current. I can also observe the current displayed on the CA and then adjust RShunt on the CA until the current displayed on the CA matches that of the DVM. It should not be necessary to account for the quiescent current of the controller (about 80mA) as that is included in the reading on the DVM. I want the CA to read the total current being drawn from the supply, including the residual load of the controller circuitry and the CA itself.
John in CR wrote:FWIW you divide the number of magnets by 2 to get the number of poles, and the tooth count is commonly referred to as the slots, so your motor is an 8 pole 18 slot motor. I bring this up in case you want to dig into some research, because the manufacturer may have done some special things with the windings that are possible with 8 pole 18 slot motors.
I'm using nomenclature consistent with this chart:http://forumrc.alexba.eu/nutpol_e.htm
from this web site:http://www.bavaria-direct.co.za/models/motor_info.htm
The box on the chart corresponding to "16 poles" and "18 teeth" gives the exact winding of the BMC "600w" and "300w"motor.
John in CR wrote:Have you tried running the motor with no accessories connected like the CA, cruise control, etc? It's possible they could be creating your issues. Personally I don't use the speed or current limit functions available in the CA, so I don't connect the CA wire for the throttle. I use the CA only as a measurement tool and don't want it ever overriding my own input. The CA does this only through the throttle wire.
Yes, I have tested the controller/motor without the cruise control attached. The problem still exists (or existed, as I think I've fixed it now).
I set the controller current limit to a figure that is just above what I feel is reasonable with these motors. Trying to push more than 55-60A through these motors results in more heat than motion, so I set the controller limit to 55A. On the CA I set the limit to 50A as I feel that is enough for my enjoyment, and I don't want to be enticed into running wastefully. My recommended limits are lower for the smaller "300w" motor. I listed them in a prior message.
John in CR wrote:You also mention efficiency. How are you determining that? To know efficiency you need to know output, but our tools like the CA only give us input along with speed and distance results. Without a dyno efficiency comparisons can only be made over the long haul by comparing consumption at different settings, and creating identical loads is virtually impossible due to outside influences unless you're using some kind of pony brake in lieu of a dyno.
To measure power output at the rear wheel I use a PowerTap rear hub with a rim brake (my "pony brake") to generate the torque. It works reasonably well.http://www.cycleops.com/products/power-meters.html
I calculate efficiency by measuring power "out" with a PowerTap rear hub and dividing by power "in" with a calibrated CycleAnalyst. Absolute accuracy is around 3-5%, but relative accuracy is better. So using the same equipment and set-up I can easily discover changes that improve efficiency and changes that do not.
Unfortunately, I have been unable to test the efficiency after the most recent shunt modifications because I'm getting too much RFI from the motor/controller that is interfering with the PowerTap signal. But, I don't expect the full-throttle efficiency to change nor do I expect much change for the partial-throttle tests.
I have tested my BMC "600w" and "300w" motors here:http://mrbill.homeip.net/albums/mac_bmc ... ta_Inf.pdfhttp://mrbill.homeip.net/albums/mac_bmc ... lta_HL.pdf
and even using a Wye connection for the motor phases:http://mrbill.homeip.net/albums/mac_bmc ... ye_Inf.pdf
Other motors tested:http://mrbill.homeip.net/hybridBike.php ... encyCurves
John in CR wrote:
You should read MWKeefer's posts here http://endless-sphere.com/forums/viewtopic.php?f=2&t=18675#p272438
. The motor inside the geared hubbies he runs is a lot like the motor you have (assuming yours is neutrally timed). Your phase/battery current limit ratio seems out of whack. I think you should start over on your program settings and do like he does with a new motor and start with a 1:1 ratio and go from there. Especially now that you've modded the shunt so much you'll want to be careful with Block Time to make sure your current overshoot isn't out of hand by going too high for the controller and/or motor, but it's a valid tool otherwise in tuning your controller for optimum performance.
Thanks. I did read that thread some time ago. Most or all of the advice is about tuning the controller for hub motors rather than mid-drive or crank-drive motors, but upon re-reading I think I might experiment with a lower phase current to overall current ratio. Right now I'm using 2.5x for phase current limit (about 140A), and that seems to provide plenty of pull at partial throttle. My memory of reducing the phase current was that it reduced the torque too much at partial throttle, leading to a gut-less feel when, say, riding up a hill with a varying grade. As the hill steepened momentarily, the motor would bog down more easily with a lower phase current. At 2.5x, the motor power would increase to compensate for the increased load, keeping the bike speed constant, or nearly so. Still, I might try experimenting with it again.
I use the shortest Block Time available, 0.1 seconds. Since I'm running through the gears, I don't ever want to have the motor pulling with "infinite" torque. I'd choose 0 seconds if I could. I occasionally and accidentally "slam" the throttle when there's backlash in the drivetrain, and I'd rather not abuse my components this way.
John in CR wrote:Regarding the speed switch settings, I'm not sure what you're trying to accomplish. I don't consider any above 100% to be valid. While they may increase top speed for some motor/controller combos, there's definitely a cost in the form of decreased efficiency and more heat in the motor and controller. There are better ways to increase max speed. I only use the speed limits for 2 things, since below 100% all it does is apply that ratio to the throttle voltage. I use it to limit the max speed for people to test ride my bikes, since they're too fast for inexperienced riders. I also use a low % like 50-60% to tame a twitchy throttle response on high powered bikes.
My original thought was to see how I could use throttle limits >99%. Maybe a could have a "turbo" option for those rare occasions when I need a quicker boost off the line. In the end I decided it wasn't worth the trouble or risk.
I agree with you re: >99% speed limit settings. i.e. Set limits no higher than 99%. I use the switch to set the limits lower so that I can ride more easily with un-assisted bikers or if I hook up a higher voltage battery. I normally run at 24 volts nominal system voltage.
I did find that at 115% throttle I was able to coax a little more power out of the motor before it stalled. I also measured a slight efficiency improvement at high output power (top 1/3 of its power range), but there is a price. I didn't published the results on my website because I don't believe this operating region is safe for this controller and motor combination. The controller shuts down after a number of seconds just below the stall load--gave me a scare the first time, and while I was running a test under this condition it blew out my cruise control. I had been using the cruise control to "hold" the throttle, freeing my hands for other tasks.
John in CR wrote:You asked about long term durability. Once you get it running smooth in all circumstances (jerks or pulses of power or other symptoms you mention are unacceptable), then as long as the controller isn't getting hot it should be durable in the long-term. What you'll want to be most careful of is partial throttle or modulating your throttle going up hills. That's how phase currents can get out of hand and fry a controller. This is another instance where a much lower ratio of phase current limit to battery current limit will prove beneficial for you, and since you have lots of hills keeping Block Time at the lowest setting is probably a good idea.
I agree that smooth running without hiccups or untoward noises is a good sign. I've already got Block Time as low as it will go. I will take your suggestion and see if I can reduce the phase current so that performance is still acceptable, especially if doing so reduces the likelihood of damaging the controller under unusual operating conditions.
I find that the motor gets warm in proportion the power it is called upon to produce (or transform). The controller gets warm the higher the power as well, but it also gets warmer if power is held constant while the throttle is reduced. In practice when there's a little breeze on it from forward motion neither the motor nor controller get more than warm. Even after slowly climbing a steep hill on a hot day, the motor and controller are not so hot that one can't grasp either firmly with a hand. Bench testing is always hardest on heat-generating parts because there's no air movement around the parts that get hot. Sometimes when I'm testing it helps to set up a fan to blow on the motor and controller.
John in CR wrote:The last thing I want to bring up is regen. Since you use brakes so much that you're worried about rim temps, then you really need regen. If you ride your ebike always under power and not sometimes pedal only, then you will absolutely love regen braking. It's a tremendous safety factor coming down hills, because brake fade is non-existent so your mechanical brakes are always fresh and cool and ready for emergency stops. It also greatly reduces brake maintenance. Start with the lowest setting which is 0, and if the braking forces is still too strong you'll need to modify your shunt in the other direction to lower the actual regen current limit. On my extreme power ebikes (one at 12kw and the other now at 20kw), I need all the regen force I can take to help get these bikes stopped, but on my moderate power ebikes I like a nice gentle regen force. It takes a bit of time to learn how far ahead of a turn or stop to activate regen, but it's silky smooth, and the light force works great coming down hills to keep speeds down without using the regular brakes.
I've looked into regen a number of times. It isn't practical on my bikes for a number of reasons.
1) I'm using a through-gears mid-drive or crank-drive, so I can't put braking force through the drivetrain. It would require braking tension be transferred through the "return" chain run, through a derailleur cage that isn't designed to handle a tense chain. It would also require an unavailable locking freehub that can be locked remotely by a cable connected to a lever on my handlebar so that my rear wheel cluster doesn't freewheel when braking is engaged. Too complicated.
2) I could add a second motor, say a DD hub motor the front wheel and a second controller. But, then I have to live with the added drag when I'm not braking and the added weight of the additional hardware. My batteries would also need to be able to handle the substantial reverse current. I often ride with more than one battery in parallel connected through Schottkys, so that would block any regen current. In the end it's not practical.
If braking and not recapturing energy is the objective, I'd probably do better with an aerodynamic brake, a parachute or drag flaps, but that also requires additional hardware, levers for deployment and complexity.
I've settled on using a large disk brake on the rear of one of my bikes, and on the other a rim brake with a sturdy, wire-bead and well-fitted tire that has no bead damage from too many installations/removals. An easy and relatively cheap. I haven't had any blow-offs since I started this protocol. When I replace my rims I will choose wider, heavier rims with more metal, preferably with an "aero" profile as these dissipate heat better than box cross-section rims.
John in CR wrote:Whatever you learn about your motor, please share, since they seem to be good quality motors, but controller matching has been an issue that keeps many away from using them.
These are excellent motors for the price if you're willing to get your hands dirty and clean them up for your use. So far they're the most efficient motors that I've tested, with a conveniently broad efficiency peak. They were, after all, designed for single-speed systems (Currie, US-ProDrive, etc.).
One advantage as I see it is they do not use rare earth magnets, just a composite magnet ring held closely to the stator teeth, so there is less danger of overheating the motor and destroying the magnets. I did overheat one of the smaller 300w motors once by pumping 60A through the coils, and the result was cooked enamel on the wire. The motor still worked fine afterward, but the wire looked burnt.
The only thing that could be improved is the ability of the motor to dissipate heat better. As it's an out-runner all heat generated in the coils is transferred through the central core to the face plate. That may be one reason the internal controllers fried easily on these motors as they are mounted and potted on the inside of the faceplate.
The heatsink fins on the cover rarely get hot enough to do any good as the cover has little metal in contact with the faceplate. Fortunately, if it's set up right the motor runs efficiently, so it doesn't generate too much heat in the first place.