Building an e-bike: Generic MP4 questions

[Chris2015]

I am looking at getting the Magic Pie 4 along with the 48v 10ah battery with the MP4.

1# Is there a good cheap bike you recommend I buy to make this kit work with (my current cheapish $250 full suspension canadiantire bike is getting older, and might as well replace it)?

2# Do you recommend a thumb or twist sensor? Ive read that some people say thumb is a bit safer as its harder to accidentally max it if you slip or hit a bump, but on the other hand, twist is more comfortable.

3# How does cruise control works? It says "Control switches for cruise control and optional horn and lights.", does that mean it can do cruise control, but it won't work unless I buy something else like the "Smart Display for Magic Pie 4 and Smart Pie 4"?

4# From what I could tell there was 4 wires coming out of this kit. One would be brakes, the second would be the throttle, the third would be the LCD device and the 4th would be the battery… Is this right?

5# Does this kit come with a torque arm or usb cable?

[Bikemad]

Hi Chris andto the forum.

The choice of bike will depend upon your own preference but I would go for something with steel dropouts for the rear wheel rather than aluminium.
If you buy one with the gear changers combined with the brake levers, you will need to use different gear changers when you install the GM brake levers.
A bike fitted with hydraulic brakes also means that the GM Brake levers with the safety power cut off switches cannot be used.

I much prefer to use a twist throttle as I find the thumb throttle can be a bit too jerky to operate at times. The biggest problem with a twist throttle is trying to use it when you also have a twist grip gear change. I consider lever style gear changers and a twist throttle to be the best combination:



The cruise control is standard on the MP4s and SP4s and operates by saving the throttle signal voltage at the time the cruise button is pressed.
In normal use you would set the throttle to maintain the required speed and then press the cruise control button allowing you to release the throttle and still maintain the set speed. Pressing the cruise button again, or applying the brakes, cancels the cruise setting. On the earlier versions of the Magic Pies and Smart Pies the throttle was disabled while the cruise control function was in operation, but on the later MP4s and SP4s the throttle will override and automatically cancel the cruise control function.
The Smart Display is very useful if you are using the pedelec sensor as it allows you to select different levels of assistance as you are riding.

The wiring of the MP4 is basically the same as the MPIII even though it has different connectors to the ones shown in this diagram:



The kits do not come with the USB programming lead or torque arms, and I don't think GM China even sell torque arms, but you should be able get them locally from GM Canada.
The programming lead is an optional extra but is essential to have it if you want to to be able to change the controller settings for different battery voltages or to reduce the maximum speed and power to comply with legal requirements.
Dependant upon your riding style, you might also want to reduce to acceleration setting to provide a smoother throttle response or even reduce the available motor power to extend your range.

Hopefully this will have answered most of your questions.



Alan
 

[ElectricEssence]

I had the smart display and PAS sensor installed with my Magic Pie 4 but I can't get it to work. I've talked to Gary and he was also unable to get his own cadence sensor working with his 48v systems and he suggested  maybe the cadence sensor doesn't work with 48v batteries.  Alan can you shed any light on this?  I've since returned the smart display for a refund and plan to buy the torq sensor next.

[Chris2015]

Maybe ill try my current bike and see how it works.... I think its steel (magnet seems to stick to it, even tho its rather weak compared to how it sticks to my shelf).

By the way, how well does this kit work with freewheels? By the sound of it, this does not come with a freewheel.... So id have to transfer the one from my existing bike.... By the way, what are the dimensions of this? Im worried my freewheel + the width of this motor = too wide for my bike.

If you buy one with the gear changers combined with the brake levers, you will need to use different gear changers when you install the GM brake levers.

Don't think ive ever seen a gear changer combined with a brake lever (so maybe im misunderstanding you?). Right now im thinking of using my own bike, or something like this:
http://www.canadiantire.ca/en/pdp/schwinn-suspend-mens-26-hardtail-mountain-bike-0711381p.html#.VU6lfZPW4Vc

A bike fitted with hydraulic brakes also means that the GM Brake levers with the safety power cut off switches cannot be used.

Why not? Arent those brake levels just pulling a wire and sending the brake signal to the motor? My current bike has disc brakes on the front only (buth both brake levers look the same). Also wouldn't the MP4 have some sort of internal braking if it can also do regenerative braking?

I much prefer to use a twist throttle as I find the thumb throttle can be a bit too jerky to operate at times. The biggest problem with a twist throttle is trying to use it when you also have a twist grip gear change. I consider lever style gear changers and a twist throttle to be the best combination:

Ok, I will lean towards twist then.

The kits do not come with the USB programming lead or torque arms, and I don't think GM China even sell torque arms, but you should be able get them locally from GM Canada.
The programming lead is an optional extra but is essential to have it if you want to to be able to change the controller settings for different battery voltages or to reduce the maximum speed and power to comply with legal requirements.
Dependant upon your riding style, you might also want to reduce to acceleration setting to provide a smoother throttle response or even reduce the available motor power to extend your range.

Those prices are crazy tho I usually spend about $2 on a usb cable, the idea of spending that much on a cable.... It's hard to swallow.

Hopefully this will have answered most of your questions.

That a good chunk of them, thanks for your time.

[Bikemad]

I had the smart display and PAS sensor installed with my Magic Pie 4 but I can't get it to work. I've talked to Gary and he was also unable to get his own cadence sensor working with his 48v systems and he suggested  maybe the cadence sensor doesn't work with 48v batteries.  Alan can you shed any light on this?

I originally tested my MP4 with the Smart Display and pedelec sensor using a 48V battery and it worked fine. The pedelec sensor only operates on a 5V circuit so the 48V battery shouldn't make any difference to its operation.
If the pedelec or the Smart Display unit does not work it is more likely to be due to the controller itself, as some versions of the vector controller are not able to support the pedelec function.

By the way, how well does this kit work with freewheels? By the sound of it, this does not come with a freewheel.... So id have to transfer the one from my existing bike.... By the way, what are the dimensions of this? Im worried my freewheel + the width of this motor = too wide for my bike.

A 6 speed freewheel unit fits most frames but some 7 speed freewheels may require an additional spacer washer and steel frames can usually be spread slightly with a bit of gentle persuasion to allow the axle to fit inside the dropouts.
 
This 18 year old 15 speed bike was only fitted with a 5 speed freewheel and the rear dropout spacing was just 125mm instead of the 135mm width more commonly found nowadays, so I ended up using a scissor jack to widen this steel frame 10mm to accommodate a Smart Pie:







I have a Shimano 7 speed "Megarange" freewheel fitted to my MP4 and it did not require any additional spacer washers or widening of the dropouts:



If your bike is currently fitted with a cassette and you need to buy a freewheel, I would recommend finding one with an 11 tooth sprocket as it will help your legs to keep up with the motor without having to pedal ridiculously fast.

The GM hubmotors require the use of the older style threaded freewheel, not the more modern splined cassette that is fitted to a freehub axle:

Don't think I've ever seen a gear changer combined with a brake lever (so maybe im misunderstanding you?).

Unfortunately, I have this trigger action style of changer fitted to one of my bikes and it is a real pain to use:



I have had to fit a separate brake lever to operate the regen and because the gear change is sequential I can't change through the gears fast enough to keep up with the acceleration of the motor on the level.

A bike fitted with hydraulic brakes also means that the GM Brake levers with the safety power cut off switches cannot be used.

Why not? Arent those brake levels just pulling a wire and sending the brake signal to the motor? My current bike has disc brakes on the front only (but both brake levers look the same). Also wouldn't the MP4 have some sort of internal braking if it can also do regenerative braking?

Hydraulic brakes don't have cables, they use a small piston on the brake lever to transmit the pressure through fluid filled tubing to a larger piston in the brake caliper. the difference in piston size multiplies the force that is actually applied to the brake pads, and the fluid in the pipe does not suffer from the friction that is caused by the inner cable rubbing against the outer cable on conventional braking systems (especially if the cables get rusty).



Although your bike has a disc brake, it is operated by a mechanical caliper and cable not hydraulics, which is why your brake levers look the same.

The Magic Pie does not have a physical internal brake, it simply opposes the magnetic force of the magnets to produce an electromagnetic dynamic braking effect which slows the wheel down and can also produces surplus energy that is used to charge the battery at higher speeds.

Those prices are crazy tho I usually spend about $2 on a usb cable, the idea of spending that much on a cable.... It's hard to swallow.

It is not just a cable with a plug on each end, the large USB connector plug contains a circuit board populated with electronic components which basically translates the data flowing between the controller and the PC/laptop.

Alan
 

[Chris2015]

So mine looks like 13.5cm, so I guess that is a good sign.

But if I (need) to replace the freewheel/cassette thing, then that means id also need to replace the mid cassette along with a new chain so it all fits right?

Also thanks for the 11 tooth sprocket tip. I will keep an eye on that. Funny thing is, my current 21 speed bike is so slow, even with just leg power.... Looks like it has 13 tooth sprocket, while the 'casette' in the middle of the bike is only 7" (while my previous bike it was 8"). So I am more than happy to replace it.

Although your bike has a disc brake, it is operated by a mechanical caliper and cable not hydraulics, which is why your brake levers look the same.

Ah, I understand now.

The Magic Pie does not have a physical internal brake, it simply opposes the magnetic force of the magnets to produce an electromagnetic dynamic braking effect which slows the wheel down and can also produces surplus energy that is used to charge the battery at higher speeds.

So it sounds this regenerative breaking thing is more of a marketing thing then, as I cannot imagine much energy is saved using this method. Also aren't batteries designed to be charged using the charging port and not output port?

The cruise control is standard on the MP4s and SP4s and operates by saving the throttle signal voltage at the time the cruise button is pressed.

In normal use you would set the throttle to maintain the required speed and then press the cruise control button allowing you to release the throttle and still maintain the set speed.

If I use a 48v battery, wont the motor be using 48v 100% and only the amperage changing? I am not an electric guy, but I always thought voltage stayed the same in a circuit and only amperage was decreased/increased as needed.

Either way, are you sure it works the way you described? That if I set a speed, the controller will maintain that speed even up a hill (assuming its powerful enough to do it). So in other words, if I set it to ~~10 KPH and went up an incline, it would be smart enough to increase the power to maintain that ~~10 KPH by increasing the wattage? Or similarly, if I set it to ~~10 KPH on a flat surface and started pedaling so I was going 20KPH on my own, it would be smart enough to cut back the power?

Also another question... Any whispers of the MP5? I tried sending an email about this to GMC late last week, but haven't heard back yet.

[Lewis Balentine]

...
The programming lead is an optional extra but is essential to have it if you want to to be able to change the controller settings for different battery voltages or to reduce the maximum speed and power to comply with legal requirements.
...
Alan

Also requires Microsoft Windows based computer.

[Bikemad]

So mine looks like 13.5cm, so I guess that is a good sign.

But if I (need) to replace the freewheel/cassette thing, then that means id also need to replace the mid cassette along with a new chain so it all fits right?

Also thanks for the 11 tooth sprocket tip. I will keep an eye on that. Funny thing is, my current 21 speed bike is so slow, even with just leg power.... Looks like it has 13 tooth sprocket, while the 'casette' in the middle of the bike is only 7" (while my previous bike it was 8"). So I am more than happy to replace it.

There should be no need to replace the chainwheel or the chain itself, but if you decide to use a chainwheel with a substantially higher number of teeth then you might need a slightly longer chain if you find that the existing one isn't quite long enough.

So it sounds this regenerative breaking thing is more of a marketing thing then, as I cannot imagine much energy is saved using this method. Also aren't batteries designed to be charged using the charging port and not output port?

Regenerative braking will usually start to charge the battery at speeds above 15mph, and at higher speeds the current generated can be fairly high.
A few years ago I carried out a test with my MPII (with a slightly modified shunt) using a pair of watt meters with one connected in reverse to measure regen current, and here are the results of a short test run using the 25.9V 10Ah LiPo pack:

Units Measured	Under Power	During regen
Voltage (Volts)	27.41 min	29.47 max (@ 22mph)
Current (Amps)	36.39	16.37 (@ 22mph)
Power (Watts)	997.4	482.5 (@ 22mph)
Capacity (Ah)	0.626	0.042

         
I calculated the regen to be ~6.7% of the power used, therefore the range should also be extended by an additional ~6.7%. At slow speeds it won't really make any difference (apart from saving wear on your brake pads), but it really can make a noticeable difference at higher speeds.

Most batteries will accept a charge through the power output connection as well as (or sometimes instead of) the charging port.

If I use a 48v battery, wont the motor be using 48v 100% and only the amperage changing? I am not an electric guy, but I always thought voltage stayed the same in a circuit and only amperage was decreased/increased as needed.

Either way, are you sure it works the way you described? That if I set a speed, the controller will maintain that speed even up a hill (assuming its powerful enough to do it). So in other words, if I set it to ~~10 KPH and went up an incline, it would be smart enough to increase the power to maintain that ~~10 KPH by increasing the wattage? Or similarly, if I set it to ~~10 KPH on a flat surface and started pedaling so I was going 20KPH on my own, it would be smart enough to cut back the power?

The voltage is not switched 100% to the motor, the Sine Wave controller uses wave pulses that vary in size/duration in relation to the throttle position.
If you had an ammeter connected to your battery and set your cruise control at 10mph on the level you would see the current increase when you come to an up hill incline and also decrease as you went faster down hill, or if you pedalled faster than the set cruise speed on the level, so yes, it does basically work as I have described.

Also another question... Any whispers of the MP5? I tried sending an email about this to GMC late last week, but haven't heard back yet.

I have not heard anything from China about an MP5 as yet, but I suppose it is inevitable that the MP4 will be updated at some point.

Alan
 

[Chris2015]

Part of me wants to wait to get the latest, but the other part of me wants this now so I can get the most usage out of it this summer...

Btw, is this the freewheel you are recommending (that will work with the mp4): http://www.goldenmotor.ca/products/7-Speed-DNP11%252d32-tooth-Freewheel.html


Assuming I buy a rack in town, it seems getting the following is 100% all I need to get this to work? (since I want to skip on the LCD and pedal assist for now)?
48V10AH LiFePO4 Aluminum Cased Battery  http://www.goldenmotor.ca/products/48V10AH-LiFePO4-Aluminum-Cased-Battery.html
Magic Pie 4 (VECTOR) 26 Inch Rear Conversion Kit http://www.goldenmotor.ca/products/Magic-Pie-4-%28VECTOR%29-26-Inch-Rear-Conversion-Kit.html
7 Speed DNP11-32 tooth Freewheel http://www.goldenmotor.ca/products/7-Speed-DNP11%252d32-tooth-Freewheel.html
(2 of these) Spacer Washer  http://www.goldenmotor.ca/products/Spacer-Washer.html
Rear Torque Arm http://www.goldenmotor.ca/products/Rear-Torque-Arm.html
USB Programming Cable for Magic Pie 4 VECTOR and Smart Pie 4 VECTOR Controllers  http://www.goldenmotor.ca/products/USB-Programming-Cable-for-Magic-Pie-4-VECTOR-and-Smart-Pie-4-VECTOR-Controllers.html

That comes to ~ $1349 after shipping & taxes.

[Bikemad]

Hi Chris,

That 32-11T freewheel should be ideal for the Magic Pie but I don't know if it will require spacer washers.

One other thing you might require is the freewheel removal tool in case you need to get the freewheel unit off again, as a conventional freewheel tool won't fit over the 14mm axle. I had to enlarge the centre hole of a  standard removal tool using a 10mm diameter grinding bit in a minidrill until the tool would fit over the GM axles.

I also like to use slime filled inner tubes on my wheels as they eliminate the need to keep removing the wheel in order to repair tiny punctures.

Alan
 

[Chris2015]

Ended up sending a question to the owner and never heard back, kind of lost faith in this site a bit so I put off my order.

Now summer is half over, looks like the Magic Pie 5 is still not here, and the 26" rear Magic Pie 4 is currently out of stock. odd. Still got money set aside for this, but I'm more uncertain now.