Undocumented MagicPie behaviour

[Geoff]

I have 2 MagicPie's with 36V16A LiPo batteries purchased in late Feb 2010. The batteries finally arrived last week and I'm generally very pleased with the results. However I have 2 questions...

1. I have installed PAS detectors on both bikes. And PAS operates by default on both. Without specifically turning the PAS on. In fact there seems to be no way to turn it  off. After 2-6 turns of the crank the motors kick in... and power up to full straight away. Its a bit disconcerting. I'd like to be able to turn the PAS on and off without physically disconnecting the sensor.

2. Occassionally, after using regen braking one motor will stop functioning. If I turn it off and back on, (at the key), the hub will beep 6 times, the charge lights will come on but the throttle will not respond. If I leave it for about 5 minutes it will turn on normally and function fine. It doesn't seem to be overheating. I can place my hand on the motor housing and it will just feel warm.

Any ideas on these?

[Bikemad]

Geoff,

If you haven't used the throttle switch for lighting, it should be possible to use it to turn the PAS on and off by cutting the Red +5V supply lead going to the pedelec sensor, and connecting the two cut ends to the brown and yellow switch leads (make sure the joints are safely insulated).

The cutting out you describe does sound like it's temperature related. Although the hub casing may feel only warm, the stator inside the hub will be much hotter, but as is separated from the cover by air, it will take a while for the air to conduct the excess heat away from the stator. Hence the 5 minute wait. When it cools down to a safe level it will then work again as normal.

Is the one that's cutting out being ridden faster or does it have have smaller wheels or carry a heavier load by any chance? As all of these factors will have a noticeable effect on the amount of current (and also heat) being generated by the regenerative braking.

Alan
 

[Geoff]

Thanks for the response Alan,

If you haven't used the throttle switch for lighting, it should be possible to use it to turn the PAS on and off by cutting the Red +5V supply lead going to the pedelec sensor, and connecting the two cut ends to the brown and yellow switch leads (make sure the joints are safely insulated).

I'll give this a go. Though I wonder why its on by default. It seems to be counter to the documented behaviour. It would also be great if the amount of power applied to PAS could be controlled. My wife is getting back on her bike after sometime and finds it scary when it just takes off at full speed with no way of moderating the power.

The cutting out you describe does sound like it's temperature related. Although the hub casing may feel only warm, the stator inside the hub will be much hotter, but as is separated from the cover by air, it will take a while for the air to conduct the excess heat away from the stator. Hence the 5 minute wait. When it cools down to a safe level it will then work again as normal. Is the one that's cutting out being ridden faster or does it have have smaller wheels or carry a heavier load by any chance? As all of these factors will have a noticeable effect on the amount of current (and also heat) being generated by the regenerative braking.

I suspect that you are right here. I'm pretty heavy at present (110kgs) and the bike has 700c wheels. I'll ease back on using the regen. I've put the regen on a seperate switch instead of using the supplied brake levers.

Can anyone confirm if there is a way of changing the amount of pedal assistance supplied by the motor?

[Leslie]

Hi Geoff.

I can confer with Bikemad.


Those red buttons on the throttle have been used as PAS bypass on a few different bikes.

I would rid of it all together.

The point of PAS is to make people rely on the pedals by making the throttle unreliable.  Its a case you must pedal the bike because its got pedals but if you ever need the motor to save your dear life ever forget about it.  They say its safer not to have people rely on a motor that may fail.

Not using PAS IMO doesnt create a rely upon the motor at all times situation.

You just pedal when you need, the absence of PAS doesnt cut peoples legs off.

Ouch 110 kgs on a 28" wheel.  Your combined weight and bike = more than mine with 35kgs of lead strapped to my frame.

But I can tow another 50 kgs on top of that with a 26" wheel on a HBS..

Alan.

The regen on 28" wheel is perplexing me here.

The larger radius of the wheel obviously relates to torque vs regen current supplied to the FETS gate.  The 28" wheel would be more wheel torque vs regen, where as a 16" wheel would amount to more RPM vs regen.

How does the differences relate in the real world to the end user?

Those fets are a wide channel for current each.

Could it be when in regen mode, high RPM (16") stresses the controller and high torque (28") stresses the motor?

[GM Canada]

Hi Geoff

I also would say just unplug it. I had it hooked up on my first conversion and also found it difficult to use. It would kick in at full throttle after a little peddling and the scary part was it would continue to go full throttle for a few seconds after releasing the throttle.

I vote, unplug it!

Gary

[GM Canada]

Ouch 110 kgs on a 28" wheel.  Your combined weight and bike = more than mine with 35kgs of lead strapped to my frame.

But I can tow another 50 kgs on top of that with a 26" wheel on a HBS..

This weight should still not impede the use of his Pies. I did a rough calculation of my weight, bike weight, conversion kit with 2 batteries and gear carried to go to work and it came out to over 160kgs. Thats on a HBS 48v1000w , the pie should still have more torque and should still be able to handle this. I'm not recomending this but sometimes reality takes over.

Gary

[Leslie]

Ouch 110 kgs on a 28" wheel.  Your combined weight and bike = more than mine with 35kgs of lead strapped to my frame.

But I can tow another 50 kgs on top of that with a 26" wheel on a HBS..

This weight should still not impede the use of his Pies. I did a rough calculation of my weight, bike weight, conversion kit with 2 batteries and gear carried to go to work and it came out to over 160kgs. Thats on a HBS 48v1000w , the pie should still have more torque and should still be able to handle this. I'm not recomending this but sometimes reality takes over.

Gary

Thats what I meant.  If my meagre HBS36 500 watt (200 watteva) can do the weight it pulls home some days a 28 inch pie should find it easier.  And doesnt he have dual drive?

Right now I think we should look at a few things more carefully and explore all the possibilities of whats going on here.

Not a bad idea but some variables cn be explored.  Like the rubber brake for the front rim's brake switch slows the rear and the reversed.

Crossing the braking action can make it smoother for both wheels.  If regen and brakes are applied over the frame evenly the regen maybe shared more evenly.

Geoff

I have 2 MagicPie's with 36V16A LiPo batteries purchased in late Feb 2010.

Interesting combination.

Geoff can I ask a few questions.

These are Lipo not lifepo4?

Two packs or one and how are they configured to the controller?

This is a dual drive?

If, so it wouldn't be by any chance its the front wheel cutting out?

And what is the C rating on you lipo's?

Thanks.

[stijn]

Hello, just for the record, I've got my Magic Pie just a few weeks now. My bike with 700C front wheel Magic Pie and 4 12V SLA 10Ah batteries is just over 50kg. Add my weight (75kg) and the kids trailer (50kg) and the pie has to pull over 170kg. Fully loaded at 24V I'm getting 20km/h and a range of +50km. At 36V 30km/h and +30km and at 48V easily 40km/h and +20km.
At the start the batteries give 54V and I must say the torque is huge. Without trailer and with heavy pedaling I easily reach speeds of +45km/h. I didn't install the PAS and find the regenerative braking hard to use as it slows down the bike real quick (almost immediately to full stop). Nevertheless it's so much fun to pass by and leave behind a group of trained cyclists with two kids laughing at them in the trailer...

[Bikemad]

I would not hesitate to go for the Magic Pie, because it has plenty of torque making it ideal for your needs.
The Pie may be heavier, but its large diameter and extra poles/magnets give it much greater torque.

I must say the torque is huge.

I was just going to say that you made the right decision in buying the Pie, but it sounds to me like you might already know that!

Alan.

The regen on 28" wheel is perplexing me here.

The larger radius of the wheel obviously relates to torque vs regen current supplied to the FETS gate.  The 28" wheel would be more wheel torque vs regen, where as a 16" wheel would amount to more RPM vs regen.

How does the differences relate in the real world to the end user?

With a small wheel, the regen is far more effective at actually slowing the bike down quickly, so it only works harder, but for a shorter period of time.

A larger wheel exerts more leverage, making it more difficult for the regen to slow the speed down, and it therefore has to work for a longer period of time, but at a reduced rate compared to the smaller wheel.

The velocity, gradient of the hill and the total combined weight of the bike and rider will ultimately determine how much load is put upon the regen. The higher the load, the greater the generated current (and also the heat) will be.

I think the voltage generated at high speed (before regen is used) may be more of a problem for the controller with a small wheel than with a big wheel.  The voltage being generated will be relative to the wheel speed, therefore a 16" wheel will produce ~75% more volts than a 28" wheel running at the same road speed. If the voltage goes too high, something is likely to fail. (ie. the FETs or capacitors etc.)

I have 2 MagicPie's with 36V16A LiPo batteries purchased in late Feb 2010.

Interesting combination.

Geoff can I ask a few questions.

These are Lipo not lifepo4?

Two packs or one and how are they configured to the controller?

This is a dual drive?

If, so it wouldn't be by any chance its the front wheel cutting out?

And what is the C rating on you lipo's?

Thanks.

The clue was in the initial post: 

I have installed PAS detectors on both bikes

I suspect the batteries are LiMn not LiPo.

Alan
 

[Leslie]

Hello, just for the record, I've got my Magic Pie just a few weeks now. My bike with 700C front wheel Magic Pie and 4 12V SLA 10Ah batteries is just over 50kg. Add my weight (75kg) and the kids trailer (50kg) and the pie has to pull over 170kg. Fully loaded at 24V I'm getting 20km/h and a range of +50km. At 36V 30km/h and +30km and at 48V easily 40km/h and +20km.
At the start the batteries give 54V and I must say the torque is huge. Without trailer and with heavy pedaling I easily reach speeds of +45km/h. I didn't install the PAS and find the regenerative braking hard to use as it slows down the bike real quick (almost immediately to full stop). Nevertheless it's so much fun to pass by and leave behind a group of trained cyclists with two kids laughing at them in the trailer...

 

Thats awesome.

I have a dirt bicycle comming together with a 20" wheel at the back.

I hope to own one soon too.

[Geoff]

1 MP per bike.
1 GM supplied 36V16A LiFePO4 battery per bike.
One bike is a Giant Suede (26" wheel) http://www.giant-bicycles.com/en-au/bikes/model/suede.slate.blue/5321/39386/
The other bike is a Giant Cypress 2 (700c wheel) http://www.giant-bicycles.com/en-au/bikes/model/cypress.2/5329/39116/

The Cypress 2 gave me around 50k range over varied terrain with speeds on the flat of around 25-30kph I'm pleased with that.

It's cut out on me 4 times now with around 150K of use. Each time it dies with no warning and comes back after about 5 minutes of rest. After it fails it will beep 6 times. I can't find in GM's documentation, or on their website, or within this forum what 6 consecutive beeps means as a diagnostic code.

After it has failed once and recovered it will then continue to work for up to 30 minutes without problem. From memory each time it has failed has been on flat terrain but after using regen braking.

I'm happy to accept that overheating is the problem but some information about the diagnostic beeps would be helpful

[Geoff]

Its not much point trying to convince me on the facility of PAS or the desirability of turning it off. Its a given for me that it work as advertised.

I've ridden other bikes where the PAS works very well. It was part of the MP feature set that helped me make my purchasing decision.

Currently it doesn't work as advertised. I'm wondering if anyone knows if there is a reason why this is the case and if there is a way of making it work properly.

Switching it on and off is one solution, but a kludge.

Making it work as advertised, (ie turn on by pressing Cruise twice and off by cycling power) would be better.

Best of all would be finding a way of changing the amount of assistance it provides.

Has anyone else noticed this behaviour and interested and wanted it to work properly?

[GM Canada]

Thats what I meant.  If my meagre HBS36 500 watt (200 watteva) can do the weight it pulls home some days a 28 inch pie should find it easier.  And doesnt he have dual drive?

Whoops! Sorry Leslie, I guess there were to many beer bottles in front of the screen and I didn't see your entire post.

Gary

[GM Canada]

As far as I know, the only PAS that GM has that actually works is on the "Cruise Ebike". If you look at the picture you can see there is some sort of hub between the pedals and the crank.

Gary

[Geoff]

As far as I know, the only PAS that GM has that actually works is on the "Cruise Ebike". If you look at the picture you can see there is some sort of hub between the pedals and the crank.

"True Torque Sensor Pedelec" I wonder what that really means and if its for sale seperately?