Magic Pie Edge Questions

[Neven]

Hello last weekend I converted my cheap amazon commuter 700c bike with a rear wheel Magic Pie Edge kit and am loving it.  For a battery I ended up settling for a 52V panasonic GA 10 AH cell pack.  I installed 1 torque arm, and if the frame ends up being substandard and the droput snaps, I wont be too upset about having to replace it with a real frame.  Only went with a cheap bike 6 months ago because I hadn't rode one in 14 years.

I am just shy of 300 lbs and the kit can pull me 28 km/h up a 9.5% grade (with me pedaling not excessively), so I am impressed with its performance, the downside of course is the wattage was staying at 999 on the smart display, so I lowered the battery drawn current a bit since I figured I was straining the motor (now it goes 20km/h up).  One of my concerns is staying consistently at a high input wattage.  When i'm out of peak hours of transit I plan on taking the bike up the mountain I live on.  I have two routes I can take, one is 4 km at 5% avg grade, the other is 3 km at 9% avg grade.  I gave the 5% route a try today (mind you I had my panniers full of easter goodies for the kids), and I found the motor got pretty warm by the time I got home but it didn't kick out and I was still able to touch it with bare hands.  Should I be concerned about a constant load like this?  I will be doing this on avg 6 days out of 54 (shift work...yay...)

Now for the opposite question, on my way to work, I ride down that 3 km.  I average around 45 km/h down the mountain, 65km/h peak.  Do I need to be worried about damaging components braking at speeds like this?  also if I choose to go for a ride without the battery connected, is there some way I can dissipate the energy generated from the braking so I don't damage the wheel/controller.  I'm an industrial electrician with plenty of electronic repair experience so it does not need to be an off the shelf solution.

I plan on removing the throttle eventually and going PAS only but unfortunately the smart display gives an error 2 instead of the wattage when I disconnect the throttle.  Is there a separate harness made for European customers who require PAS only or perhaps a connector that will accomplish tricking the display into thinking I had a throttle connected.

Also what are peoples experience with the Magic Pies built in PAS controls.  I know its pretty harsh to use out of the box, and i've played with acceleration + ratio parameters.  With my weight, I cant really lower the battery drawn current further or I will need to turn off the system and go full manual on the steep hills  I plan on swapping out to a different magnet disk with more poles, has anyone done this without swapping out the sensor? In the end I may end up settling for a voltage mode PAS thats been linked before on this forum.  However it looked like the people who installed this used CA3 vs just the smart display, so i'm not sure I want to lose the PAS selection, however if people found it smooth enough to not need to adjust it, i'll be fine with it.  I wont be going for a CA3, I find it looks clunky and I want to reduce the amount of wires by the handlebars

Thank you to those who has read this far into my wall of text.

[Bikemad]

If your fame is steel, it shouldn't break the dropouts, but if you have the cassette version of the Edge (with 12mm axle instead of 14mm) I would strongly recommend a second torque arm to prevent the axle from spinning and damaging the motor's wiring.

Overheating of the controller should result in the power being cut until the controller cools down again. I have not heard of a Magic Pie motor being damaged from excessive heat.

Activating the regenerative braking at 65 km/h (500rpm) could produce very high current, which could result in excessive voltage for the controller if your battery's BMS disconnects the power going to the battery because the regenerative current is too high.

Perhaps something can be implemented similar to a wind turbine voltage regulator, so that the excess current is fed into a resistive load to prevent the voltage from climbing too high.

As 48V will drive the motor at ~360rpm, I would expect the motor to be capable of generating an open circuit voltage in excess of 66V at 500rpm.
This would not be good for the capacitors in the controller which are only rated for 63V max.
It's probably much safer to try and stay below 60km/h if you can. 

I plan on removing the throttle eventually and going PAS only but unfortunately the smart display gives an error 2 instead of the wattage when I disconnect the throttle.  Is there a separate harness made for European customers who require PAS only or perhaps a connector that will accomplish tricking the display into thinking I had a throttle connected.

After I tested an early BAC-601 Smart Display unit back in October 2014, I wrote to GM China regarding this problem and suggested that it might be necessary to supply a “dongle” (a dummy throttle plug containing a fixed resistance between the +5V and throttle signal pin) in order to overcome the error message when a throttle control is not fitted.

As I have never used my Smart Display without a throttle, I have never had to try this out, but I suspect that the throttle signal voltage needs to be ~1V to prevent the error message from being displayed.

If the signal voltage was too high it could prevent the pedelec from working.

It might be easier to simply connect a 10k potentiometer (preferably a small trimpot) across the 0V and 5V throttle connections and then adjust the throttle signal voltage (connected to the adjustable output from the pot) to 0.8~1V.
The potentiometer would allow for easy fine tuning (if needed).

Alan
 

[Neven]

Thank you Alan for the response,

I'll slow down a bit going down the mountain I guess   Now if I set the regenerative breaking to 45 amps and my battery can handle a 50 A continuous load, would this negate the current issue or is this two different things


As for the dongle, its a shame it doesn't exist.  My plan to go PAS was a bit more urgent due to my failed attempt to use the throttle switch as a enable/disable  switch.  Ended up snapping a hal sensor lead trying to get it back in place.  I decided to pull out the throttle cable and make my own dongle, just needed to find the resistor values to get this working.  I testing pinout continuity to determine the colors followed by a function of each wire.  With the differing versions of the harness wiring, I figured its best to double check.

i ended up with the following pin outs:

Light Switch Leg    o   o     Battery +
.        Battery -    o     --- 
Throttle Signal       o   o     4 Volts

With having a slow work afternoon, I decided to throw the bike on the bench upside down and try out splicing the 4V to the signal wire.  I expected the wheel to go full tilt but found the reverse to be true, no throttle at full voltage.  This made life easy, only need to splice those two wires in the dongle, no resisters needed.  Makes sense to me too, if the HAL burns full voltage, then you wont be stuck accelerated, if the HAL burns open, then you have 0V and an error state.  I ended up Using a scotchlock crimp, staggered the other wires, siliconed around the wires, heatshrink in several layers, and plugged in the dongle.  Works like I wanted it to.  Now I just need a better magnet for my PAS sensor.

[Bikemad]

Although your battery can happily supply 50A continuously, this does not mean that you can also charge the battery at the same 50A.

Without knowing the maximum recommended charging voltage for your particular battery, it is difficult to say whether high current regen will be detrimental to the health of the battery (or whether the BMS controls charging current returning through the power output wires). 

The throttle connections on the Edge should be the same as the Magic Pie 4 and Smart Pie 4 shown here:


The throttle signal is usually ~1V at rest (if it drops below 0.8V it triggers a throttle fault) and around 4.25V at full throttle.
The controller uses a working range of between 1.25V and 3.25V to go from minimum to maximum power/rpm.

If you had rewired the lighting switch to open and close the throttle signal circuit, it would still have produced the error on the Smart Display with the throttle turned off, just like unplugging the throttle connector does.

However, if you had rewired the lighting switch across the +5V and throttle signal wire (similar to your current setup, but switched instead of permanent) then the motor would be stuck on full throttle when the switch was pressed (assuming the controller was powered on before the lighting switch was pressed).

If the controller is powered on while full throttle is applied (like yours is) the controller has an inbuilt safety function that prevents the throttle from working until the signal voltage drops below ~1.25V.
Fortunately for you, it appears that this does not also prevent the PAS from working.

I suggest that you don't unplug your modified throttle cable and plug it back in again while the controller is powered up, just in case the low throttle voltage error does not disarm the throttle. 
Although, it might be a good idea to try this with the bike upside just to confirm whether or not it would be a problem if it inadvertently happened when the bike was the right way up. 

It could be embarrassing if the bike suddenly took off on its own while you were showing someone what you had modified, or even as the result of an intermittent connection caused by movement between the pins in the throttle connector, or between the metal blade of the Scotchlock and the thin copper (or copper coated aluminium?) wires in the repurposed throttle cable. 

Alan
 

[Tommycat]

Keeping an eye on this thread as I have the Magic Pie 5 and smart controller and it seems adding PAS wouldn't be too difficult...   
Although not convinced that I even want it. 

For safety so I could work on the bike with the power "hot" and not run over my feet...  I did wire the throttle switch in series with the 5 volt hall supply power. Disabling the throttle. (first removing the battery supply voltage wiring of course... ) I find it a benefit to have the error code show up as it reminds me whether the throttle is armed or not. 





Regards,

T.C.

[Neven]

I suggest that you don't unplug your modified throttle cable and plug it back in again while the controller is powered up, just in case the low throttle voltage error does not disarm the throttle. 
Although, it might be a good idea to try this with the bike upside just to confirm whether or not it would be a problem if it inadvertently happened when the bike was the right way up. 

It could be embarrassing if the bike suddenly took off on its own while you were showing someone what you had modified, or even as the result of an intermittent connection caused by movement between the pins in the throttle connector, or between the metal blade of the Scotchlock and the thin copper (or copper coated aluminium?) wires in the repurposed throttle cable. 

Alan

Gave this a test, started with the throttle unplugged, plugged in, no acceleration.  I also tried it with the throttle plugged in, disconnected, and reconnected.  No acceleration either.  So it seems safe to me, either way though, I always hold down my brake at stops.

[Neven]

Keeping an eye on this thread as I have the Magic Pie 5 and smart controller and it seems adding PAS wouldn't be too difficult...   
Although not convinced that I even want it. 

With the GM supplied PAS sensor/magnet combo, its pretty rough on the higher PAS settings, I tend to keep tapping cruise control until it lines up perfectly for when it the PAS kicks in.  I keep at my PAS ratio at 100 and my acceleration to 80 for now.  Now I just need to figure out where to pick up magnet disks locally.  I know GRIN is local, but not sure if they only sell to dealers.

Now as for my experience pushing the bike build so far:

I have have made 3 attempts at the full climb home (for those locals, im in westwood plateau, vancouver region).

#1 the 5% avg grade route, this convinced me to edge up the max current to 19 amps because I was exhausted after it.

#2 I attempted the 9% grade route...  this proved too much for the Magic Pie edge with my size.  after around 1.5 km of the 9% grade
followed by a short stretch (300meters) of 12%, the motor kicked out and it was hard to even push it.  I unplugged the battery.  rode down a short incline (luckily on route) to help air cool it, then flipped the bike upside down, reconnected, and had the motor run for a good 10 minutes no load to increase the air flow around the controller.  This worked and there no longer was any resistance.  so I rode the bike down further, and gave a running start to the next big climb.  Hopped off when I hit 15km/h since I didn't want to push the motor yet, walked the rest of the way home (15 minutes).  I learnt my lesson.  Stick with the longer 5% route.

#3 was to confirm the motor wasn't fried, I went for the 5% again, and it handled it fine, but still was a bit tiring near the end, so I upped my amps a bit more.

I'm pretty pleased with the results considering my size, and it looks like this bike kit will actually entice me to be more physically active as it makes the ruthless climbs (to a fat person) tolerable enough to attempt.  Also pedaling around with the kids today, I liked how little drag you feel without using motor, not cumbersome at all.

Now for my next endeavor, finding the right horn to connect, as I have no handle bar space for my bell now :/  I'm concerned more about alerting pedestrians so I don't want to scare the crap out of them.