Pedal assist cuts out for a few seconds when I hit a bump or go over bumpy terra

[Phil Booth]

Pedal assist cuts out for a few seconds when I hit a bump or go over bumpy terrain.

Has anyone had this problem before.
With pedal assist cuts out on bumpy terrain.

Also is there a way around the maximum rpm setting? As I have a 20 inch wheel and a maximum rpm of 380 isn't enough. It's only like 22km an hour. We don't have any restrictions here in New Zealand.

Cheers

[Bikemad]

Hi Phil,

Losing power while riding over bumpy terrain etc. is usually caused by a poor connection (or sudden movement of one of the brake levers) which causes the momentary cut in the power.

Closely check all connections on the battery wires, especially the contacts on the main battery connector plug/socket.
Sometimes the key switch contacts can also be affected by physical movement of the heavy gauge wires connected to them.

If any of the Battery Gauge LEDs on the throttle momentarily go off and on again when you hit a bump, it would indicate a momentary loss of the battery power.
If the Battery Gauge LEDs all remain lit, but the motor is cutting out, It could be due to activation of a brake switch, or an intermittent break in the pedelec signal (check all three connections on the pedelec sensor connector for secure and clean contacts).

To check for a brake switch fault, you can temporarily disconnect both brake switch connectors to see if it stops the problem. If the cutting out problem disappears with both of the brake switches disconnected, plug them back in one at a time to determine whether it is the front or rear switch (or its wiring/connector) that is to blame.

Regarding the maximum wheel speed, unfortunately it is not possible to easily increase the wheel speed if you are already using the 48V battery as the Magic Pie's controller will not accept a 60V or 72V battery, but 24V and 36V batteries could be replaced with a 48V battery to produce a proportionally higher maximum wheel rpm.

I just received a second MP4 rear 26" "kit" that I had the GM R&D Department rewind for higher top end speed, though lower torque. I'll be testing this unit as soon as it stops raining here in S. California! I'm being told it will get an "off road" speed of 34mph/55kph with a 48v battery.

However, it seems that GM were producing higher speed motors for some customers, which I presume had the stators wound with a "Delta" configuration instead of the typical "Star" (or "Wye").


       Delta                    Star

Delta windings are used to produce a higher rpm, but with reduced torque. 

If you have the cast 20" wheel (and sufficient room in the frame/forks) it may be possible to fit a larger diameter 16" motorcycle tyre to your 20" rim, which should help to increase the maximum speed:

Click for more details.

Alan
 

[Phil Booth]

Hi Alan, thanks so much for that.

Awesome, I love the idea of putting a motorbike tire on unfortunately I don't have enough room at the moment in my forks but I think it would be worth trying to change my forks so I could have the big motorbike tire.

I'm still having the problem of my pedal assist cutting out over bumps. It's definitely not a power problem my battery gauge LEDs, they don't go off and on or anything like that. I've triple checked all the plugs and things, I'm now going to solder the wires directly so there is no plug for the pedal assist. But it really seems like it's in the controller itself I wonder if I have a loose wire in their. I don't use any brake levers at all so it can't be them. I use a normal cable disc brake.

As for my Max speed on pedal assist. I have a 48V battery.  What I find strange is that pedal assist doesn't help me any longer after about 22kms an hour but at that point I can use the throttle to go faster. This normally wouldn't be a problem for most people but in my case using the throttle means leaning forward and using my chin in an awkward position. As I'm a C5/C6 quadriplegic so my hands are always on the pedals.

Anyway, my next thing to do is solder wires of the pedal assist. If that doesn't work I'm going to try and take the controller apart and see if there is a loose wire in there. Unless you can suggest anything else.

As for the Max RPM I'm at a loss as to why I can go faster with the thumb throttle than I can with pedal assist.

Thanks again and if you have any other suggestions for me that would be much appreciated.

Cheers
Phil
 

[Bikemad]

Hi Phil,

Have you tried altering the "PAS Ratio (0.1 times)" and "Acceleration" settings with the programming software to see if it increases the speed when using just the pedelec sensor?

It is also worth making sure that the magnet ring and the pedelec sensor are as close together as possible, but without physically touching against each other.
If the magnet ring is too far from the sensor, it can sometimes cause the PAS to be a bit intermittent.

If you make sure that all joins in the wires are well soldered, and also properly insulated from each other, it should prevent any unwanted short circuits from occurring between the soldered joints when the cable is flexed by either movement of the steering or movement caused by bumpy terrain etc..

Perhaps you could fabricate some form of plug in mouth operated throttle so that you could simply bite a bit harder to make the motor go faster?

Alan
 

[Asterix]

And if PAS ratio setting does not work, if possible with an oscilloscope, you can also analyse the electric signal that goes out from your PAS and look what happens to this signal in case of bumpy terrain.
Are your magnets still ok? Test them individually and in case of big difference between them (magnetic power) you can replace some (can be found easily as replacement).
Finally you can also try to build your own hall sensor. I did this successfully for my MP5 with a US5881 (with a 10k resistor).

First it may be usefull to try to find out what is really the effect of the bumpy terrain: is it because the controller moves in a strange manner (I rather doubt that this could be the reason), or is it the PAS that delivers strange output signals because there is something wrong mecanically at the PAS in case of bumpy terrain (that seems to me the most probable reason).

[Phil Booth]

Hi guys,
I finally got to the bottom of the problem with the pedal assist. The ground wire right at the sensor was just hang in there by a thread. I had to dig it out of the silicon and re-solder back properly.
So this is fixed now, thanks for your help.

As for why pedal assist stopping assisting me. This Is still a problem and I would like to solve.
Yes I could rig something up that I put in my mouth to accelerate from when the pedal assist stops assisting but I would rather not as you can imagine it would get a little uncomfortable and means I couldn't talk to other mates while riding not to mention I think it could look a little silly.

I've played with the pedal assist ratio and the acceleration. The settings I'm using at the moment is pedal assist 100 and acceleration 25.

It's obvious that it's just some settings put in there by golden motor for safety reasons I would imagine.

From what I've been reading can I buy a different controller? An off-road controller that allows for 450 rpm
or can I flash the controller with new default settings.
There must be some way around this problem.
I use the bike off road 95% of the time anyway.

I've just purchased a couple more Magic Pie fives as well.

So I daresay I'll be back here again trying to get those all working together.
Should be fun though, be a pretty cool bike by the end of it. Well for me anyway.

Can anyone help me get more out of my pedal assist? Please.
Surely it can't be a safety thing when I can just use the throttle to go heaps faster than using the pedal assist.
I certainly can't see the benefit safety wise to stop the pedal assist from assisting you.

Thanks heaps
Phil

[Bikemad]

Hi Phil, as previously mentioned, the maximum motor rpm is ultimately governed by the battery voltage, although the rpm setting in the controller can be lowered to keep the speed below a legal maximum level if necessary.
Unfortunately, raising the maximum rpm setting to 450rpm (or even up to the maximum 700rpm) will not cause the motor to rev any higher than its current 360~380rpm @ 48V.

Maximum accepted controller settings:

 
Incidentally, your 20" wheel should still achieve ~34.5km/h (21.4mph) @ 360 rpm. 

I suspect that you would need to be pedalling very fast for the maximum pedelec speed to be equal to the maximum throttle speed, but when you select a higher gear in order to lower your pedal rpm (cadence) it will also decrease the amount of pedal assistance.
However, it should be possible to fool the pedelec sensor so that it detects that you are pedalling a lot faster than your true cadence, simply by using a magnet ring with more magnets.

If you had a magnet ring with twice as many magnets, then the wheel speed should theoretically double in relation to your pedal speed up to the maximum motor rpm.

If you slip the chain off the chainwheel and raise the wheel off the ground you should be able to observe the relationship between pedal speed and motor speed. 

Another option (that might even cure the temporary cutting out) would be to use a voltage mode pedelec sensor and connect the output signal wire in parallel with the throttle signal wire instead of the pedelec signal wire on the controller.
This should enable the pedal speed to proportionally control the motor speed in a similar way to the throttle control, but without utilising the controller's PAS function.

Check out DirtyGinge's thread for more information.

Alan