How far can you push MP III with external controller without temp sensor?

[Juggler]

I would like to listen to opinions/arguments about how much volts/amps/watts MP III motor can safely handle?
The main idea is to add some speed and acceleration with external controller (removing stock internal MP III controller), which will require adding more volts for speed and more amps for acceleration. Not in peak mode, but in continuous mode.

[Morgen 3Eman]

With a Lyen controller and a 48VDC GM battery charged to about 56-57 VDC, my 60 Amp analog meter pegged full scale for several seconds.   Which says over 3500 watts is easily attainable.  As the speed picked up, the current dropped as one would expect. 

TTFN,
Dennis

[Andrew]

I currently run 2000w continous as the bike is used for steep up hill off roading so the watts always stay high.  54v 35a setting on a 12fet lywn controller.   The pie gets warm, but for an hour of continuous 2000w it has not over heat yet.

[Juggler]

Ho about 72V? My main purpose is to reach higher speeds!

[Bikemad]

With a suitable 72V external controller and battery using heavy duty wires the 26" Magic Pie should be able to reach about 40mph on 72V but the 20" Magic Pie can also achieve the same speed on 120V.

Alan
 

[Andrew]

I forgot to say the pie I use has had thicker phase wires put on it.  At 72v you will probably melt the standard phase wires....  I guess.

[Aliasssss]

Hello.

Mate by phase wires you mean only the wires that connect the phases to the controller or the wounds of the motors are done using a thicker wire?

[Andrew]

Hi,

I mean the three thickest  yellow , green , blue wires that come out of the motor to the controller phase.

The copper wiring inside the motor will be ok. 

I do not know how many amps the connectors/plugs will handle on the mp3.

Going up to 40mph on a bicycle is quite frightening, you do not have much time to react to anything that comes your way on a public road.

[Just]

With a suitable 72V external controller and battery using heavy duty wires the 26" Magic Pie should be able to reach about 40mph on 72V but the 20" Magic Pie can also achieve the same speed on 120V.

Alan

What's speed might be reached on 16" MP3 with 60V battery? with 72V battery?

[Bikemad]

If the windings on the stator are the same as the 26" MPIII I would expect the speed relative to the difference in wheel size to be at least 25mph on 72V and 21 mph on 60V.

If the windings are different on the 16" pie (i.e. Delta configuration instead of Star) the speeds should be a lot higher.

The unloaded speed of a motor converted from Star to Delta theoretically increases by around 73%, but the resultant torque produced will be significantly less.

Alan
 

[Just]

If the windings are different on the 16" pie (i.e. Delta configuration instead of Star)

So, how to know? I think 20" is made to run @25kmh@48V, but I'm not sure about 16"...

[Aliasssss]

Hello mate,

My MP III on a 26" (rear) wheel:

- no load (wheel off the ground) ~ 51.2Km/h. Divide maximum speed by 3.6 gives us 14.22 m/s. Now divide that by 2.085m (my wheel circumference) and you get 6.82 RPS ( revolutions per second). Multiply RPS by 60 and you get ~ 411.67 RPM,
- full load 42.6Km/h. That is me+the bike weighing 164kg. So proceed as before you get ~ 340.53 RPM.

Things to consider:
- a front MP III will be nowhere near as efficient as a rear mounted one. By efficient I mean transforming power into forward motion,
- no load speed was measured with battery 40% SoC (40% full), so probably I would get a bit more RPM with full battery,
- full load speed was measured with full battery,
- I have 4.5 BAR tire pressure, for lower pressures there will be more friction, thus some power will be lost there,
- I have road tires (Schwalbe Marathon Dureme II) so if using off-road tires there will be some additional power lost there,
- the full load speed is subjected to wind speed when testing. There was almost no wind when I tested my maximum speed. At max speed about 85% of the power is wasted on wind friction!
- because a smaller wheel size, your full load RPM will be a bit higher ( that is assuming same load bike + rider, same motor config, same controller capabilities (mine is the stock internal controller but is version II as it can provide ~32 Amps at full load during take-off. Version 1 I read it could only deliver about 15 Amps), same battery capacity and discharge rate, same drag coefficient ... and the list goes on...

I know the wheel size is different, but maybe it helps someone out there.

Cheers!

[Just]

front MP III will be nowhere near as efficient as a rear

why?

[Aliasssss]

basic physics maybe?

OK, once we agree that more weight is distributed on the rear wheel of a bike on a flat surface we are making progress.... Agreed? The actual weight distribution depends on many factors, bike frame, steering angle, rim sizes, terrain inclination, riding speed and wind speed, just to name a few, but 30% front and 70% rear is commonly used ( excluding children bikes).

Now on a flat surface while giving full throttle in both cases rear mounted and front mounted MP III(using standard internal controller), you will see that while the rear almost never breaks adherence (unless on a wet surface and/or while not perpendicular), the front pie almost always slips and looses power (wearing the tire given enough time and practice :p ). A front pie is useless on a wet surface or while riding uphill. The stepper the angle the useless a front mounted pie becomes.

Enough theory, the fact is that on dry asphalt a front pie can never climb the same hills as a rear pie can, nor it can reach and sustain the same speed.



Anyway I feel that we are getting further away from the subject than we should.

On topic now - how much have you guys pushed your MP III with external controller? If I'm not mistaking I saw somewhere on the forum almost 4000 W ... if I remember correctly...

[Bikemad]

how much have you guys pushed your MP III with external controller? If I'm not mistaking I saw somewhere on the forum almost 4000 W ... if I remember correctly...

I managed almost 4.4kW on a MkI Pie with a modified internal controller:



The torque was incredible and even allowed me to perform my first ever one handed wheelie, but the poor controller didn't last very long after delivering such a huge amount of power.

As far as I'm aware, the windings on the MPI, MPII and MPIII are all the same and I have yet to see a Magic Pie with cooked windings.

Alan