20KW 2WD having misfires (but can do a double burnout)

[methods]

The stuttering I am seeing is not related to the current limits.
It is most likely to come on when the bicycle is freewheeling faster than the throttle setting.

Example:

Say I set the throttle to 20% and accelerate to 15mph
If I then start to coast down a hill the bike will stutter around the point where the the wheel is trying to spin slightly faster than the controller is driving it.

Another way to create this situation is to cruse up to 20mph then just slightly back off on the throttle. Move the throttle around just a little big around some constant speed and stumbling can be detected.

Under full load I detect a different kind of stutter - but I know what that is. While running at 105% I get slight stuttering when in full current limit mode.

New Subject:

I laced up a 9x7 9C into a 20" wheel
I am going to first play with this on a BMX, then when I get bored I am going to put it on the rear of a downhill bike
On the front I am gong to mount a 10x6 9C in a 26" rim.
Torque in the back, speed in the front.
We will see.

Test only - not a practical bike to ride around - perhaps the worst of both worlds. Who knows. I bet it has one hell of a mid-range tho!

-methods

 

[ZapPat]

Another way to create this situation is to cruse up to 20mph then just slightly back off on the throttle. Move the throttle around just a little big around some constant speed and stumbling can be detected.

Ah, I know this bug too, happens to me just as you describe here on all my bikes. I can even play the throttle up and down around that buggy spot while I'm rolling along to make it stumble repeatedly - not a great thing to do for fun.

Yet this is not the cause of the dual controller single throttle stutter problem, just another different odd behavior of the controller.

I laced up a 9x7 9C into a 20" wheel
I am going to first play with this on a BMX, then when I get bored I am going to put it on the rear of a downhill bike
On the front I am gong to mount a 10x6 9C in a 26" rim.
Torque in the back, speed in the front.
We will see.

Sounds interesting, but how are you going to prevent automatic regen on your rear wheel when the faster front one starts pulling it over it's max speed?

For the 20" rim you could use a soft 16"X3" motorbike tire to give a pretty good comfy ride, but it's hard to find enough frame clearance for these. I had to saw off part of the sideways protruding knobs to fit mine both front and back. It would look a bit odd with the thinner and larger front tire though...

 

[tostino]

To prevent auto regen, he could delta/wye the rear wheel... but that kinda defeats the purpose.

 

[Arlo1]

It wont regen unless you apply the brakes or if you have it programed wrong.

 

[ZapPat]

It wont regen unless you apply the brakes or if you have it programed wrong.

Any controller will regen automaticaly if the motor's voltage exceeds the battery voltage. This is because of the diodes inside the FETs act as a bridge rectifier between your batts and motor.

 

[Arlo1]

Oh so you are saying if the free wheel speed is say 90 and you go 95 it will regen? Ok I never tried that yeat.
Hey methods I did alot of digging and ordered a set of Pirelli ml75 tires seen here http://www.tiresunlimited.com/ALL%20TIRES/Pirelli/pirelli_ml75.htm they are 2.5x16 and I found a 2.25 x 16 that looks cool and for the off road stuff I found an awesome one it is small and 16x something realy small I think it would fit my bike but I wanted a non knobby! if you want I will see what it is tomorow it is at work!

 

[methods]

Sounds interesting, but how are you going to prevent automatic regen on your rear wheel when the faster front one starts pulling it over it's max speed?

Damn... You caught me slipping.
I was not thinking it thru. Yea... my 20A Pedal first controller used to regen on me all the time. Drove me nuts - I would finally find a hill to pick up some speed and BURRRRRRRRRRRRRRRR the motor would start to drag

Guess it is back to the drawing board.


-methods

 

[Arlo1]

OK you need this tire its a 2.5x16 on the page it says 60/100-16 here http://www.kendausa.com/motorcycle/dual_sport.html Very small I have on at the shop and it mesures 20.7" total dia and about 2.5" wide when you squeze it to fit a bmx wheel.

 

[methods]

I want to build an eDirtbike....

-methods

 

[Arlo1]

Me too but I don't want hub motors for it I will make a chain drive! But I cant find a motor I want to do it with And I think I will need around 20ah at 24s lipo or more but I can hide that well in a stock bike frame.

 

[ZapPat]

Me too but I don't want hub motors for it I will make a chain drive! But I cant find a motor I want to do it with And I think I will need around 20ah at 24s lipo or more but I can hide that well in a stock bike frame.

I will probably try some form of chain drive on my DH bike next summer, because it'll be for going up steep mountains and I also want to remove the hub's weight to help the suspension.

However, I just downloaded a youtube video made by Ypedal yesterday of his chain drive bike (one of Matt's drives), and it's REALLY loud!

I'm not sure if I could get over that kind of noise - I like the almost total silence of the DD hubs a lot when I'm cruising through the forest or down the road.

 

[tostino]

I think you could get used to the noise when your doing wheelies on command at 40mph. I know I sure could!

 

[Arlo1]

Yeh the noise doesn't bother me as a mater of fact I want some noise so I don't get shot in the back country. I want to build a real Motocross electric bike but I think I need to find an engineer that wants my help designing a good motor. I can pull wheelies on demand on my crf250r at any speed it tops out around 70-80mph As long as I have performance and reliability like it has I will be happy.

 

[DISH]

I started reading this last night and I think I have the answer as to why motor 1 was affecting motor 2 (or the other way around) as I tried doing this a while back and had similar problems. I know what is happening but whether or not I can put it into words clearly enough remains to be seen.

I don't have the exact wiring diagram of the setup you were using so this may not be exactly what was happening in your system but once you see what I'm getting at you can probably figure out exactly what was going on with your system.
View attachment dualctr.gif
Pay VERY close attention to the voltage drop across the wires going from the controllers to the negative battery terminal as that is the key to understanding what is going on. No matter how heavy you make the wires from the battery to the controller there will ALWAYS be some voltage drop and the huge currents you are drawing only makes the voltage drop worse.

For the sake of this discussion, lets say that controller / motor 1 is pulling enough current to cause a voltage drop of 1.0 volt and the throttle control signal is 3.0 volts. Motor 2 is pulling minimal current (wheel off the ground).

Since the black ground wire of the throttle is connected to controller 1 it follows the voltage drop associated with controller / motor 1 (as it should) and adds the throttle signal to this voltage resulting in controller 1 getting the proper throttle signal, 3.0 volts.

Now controller 2...

If controller and motor 2 is pulling very little current the ground for that system will be close to the zero volt reference point in the above schematic. However, the throttle signal it is getting is now the throttle signal MINUS the voltage drop across the ground wire going from controller 1 back to the battery.

Using the example voltages of 1.0 volt drop and 3.0 volt control signal, controller 2 now sees a 2.0 volt control signal (3.0 volt controller signal minus voltage drop of 1.0 volt).

Now assume you open the throttle and motor 1 pulls enough current so the voltage drop increases to more than the control signal, lets say 4.0 volts drop on the negative lead from controller 1 back to the battery. Controller 2 now sees the throttle control signal of 3.0 volts - 4.0 volts or NEGATIVE 1.0 volt throttle signal!!!

(Ignore the voltage drop of controller / motor 1 for this next part to make things simple.)

Now if motor 2 starts pulling a lot of current and drops lets say 4 volts across it's negative battery line you now have 3 volts of throttle signal but controller 2 chassis is now MINUS 4.0 volts below the zero volt reference meaning the throttle control signal just went from the minus 1.0 volt example above to 7.0 volts!!! ( - 4.0 + 3.0 = 7.0)

It's no wonder the motors seem to be fighting each other.

I hope I got all the numbers right but in case I didn't I hope I explained things well enough that you can see what is going on.

You are ALWAYS going to have voltage drop across the wires leading to the battery. The best way of dealing with this is like Pat suggested. Get the two grounds of the controllers as close to the same potential as possible, preferably EXACTLY the same and your problem will go away...

NOTE: One might be tempted to simply tie the black wire of the throttle to BOTH controllers. Unfortunately the thin wire used to do that is not capable of eliminating the voltage differential between the two controllers as there are HUGE currents flowing in the battery side of the wiring which is where the real problem is. In your case 100+ amps !!!

PS - This is why in professional audio they use balanced audio cables to eliminate ground loops.... Or at least try to avoid them.

 

[methods]

However, I just downloaded a youtube video made by Ypedal yesterday of his chain drive bike (one of Matt's drives), and it's REALLY loud!

I'm not sure if I could get over that kind of noise - I like the almost total silence of the DD hubs a lot when I'm cruising through the forest or down the road.

I have dropped chain drive completely.
It is loud, unreliable, and (in the case where the front chain ring is driven) down right hazardous.
I know a lot of guys have gone that route but I think negates a lot of the things that make ebikes attractive.
More power too them if they are having a good time though!

I wont be doing another chain drive ebike myself.

I am with Pat... When I am in the forest the last thing I want to do is sound like a chainsaw on crack.
I like to sneak up on the critters....

-methods

 

[methods]

I started reading this last night and I think I have the answer as to why motor 1 was affecting motor 2 (or the other way around) as I tried doing this a while back and had similar problems. I know what is happening but whether or not I can put it into words clearly enough remains to be seen.

Your argument is straight forward - not hard to follow at all.
The troubling thing is that this is not happening while one motor is pumping 100A and the other is freewheeling...

In actuality - the worst cases I get is near freewheel and at very low motor loading - I am talking like 5 - 10A
At those kinds of currents with the size cabling I am running I should not be seeing volts of drop... maybe mV....

In my circuit I am bringing out 5V, GND, and Throttle from each controller and tieing them to the same potential at the Y point where the throttle is.

I suspect the reference voltage for the A/D's in the controller.
I did not see a precision reference anywhere so I believe that they are using the +5V rail.
If this is the case, anything that can be done to keep the 5V rails equal and the 5V Grounds equal will help.

I am going to try bringing out a +5V 12AWG wire and a 12AWG ground tap - as close to the uC as possible.

-methods

 

[AussieJester]

What ever happened to the beasty mountain bike build Methods? Your back using the bike the 'future spacemonkeys' mocked you for riding :-| Still..dually hub motors is pretty damn impressive mate, you need to ed-u-bicate the missus on her filming techniques though buddy, a cat is NOT more important than seeing Methy spin a front hub out of the forks sheesh! LOL ...least she caught the walk of shame back to the house though, sorry to laugh at your misfortunes mate but it was pretty damn funny, like a kid who broke his Chrissie present the first 5 minutes of playing with it hahaha...

No more chain drives hrmz...could i tempt you with a belt drive setup? oooober quiet mate and you can still have gears setup :: wink ::

KiM

 

[Arlo1]

The chain drive I am talking about using is for an E-motocross bike (not a little e-bicycle) I am talking about something I will be jumping 20-30 feet hi and over 100 feet long, Climbing coal hills, rocks, mountain sides ect, going through 3-4 feet deep mud and water and the list goes on I will not have the wheel weigh more then stock and I want all weight central like stock. My point is it will kick ass and will put all those who think ebikes are lame in there place!

 

[will_newton]

http://us.itselectric.ca/Crystalyte_Dual_Motor_controller_p/ctrl-crystal-c7220dm.htm

this was a link from another thread, but i thought of you. maybe a 100v/100A version?

wouldn't freewheeling geared hubs solve some of the issues with the regen?

and/or using dual throttles?

 

[liveforphysics]

I have dropped chain drive completely.
It is loud, unreliable, and (in the case where the front chain ring is driven) down right hazardous.
I know a lot of guys have gone that route but I think negates a lot of the things that make ebikes attractive.
More power too them if they are having a good time though!

I wont be doing another chain drive ebike myself.

I am with Pat... When I am in the forest the last thing I want to do is sound like a chainsaw on crack.
I like to sneak up on the critters....

-methods

You big pansy. Chain drive isn't the problem, your skills and your setup was the problem. You fit a flexy-mexy cyclone kit powered through bicycle chain and a derailer on your bike and hit it with 100v+100amps, and SHOCK! it wasn't reliable. Chain drive is exactly as reliable as you make it. It's also as quiet as you design it to be. The loudest part on my bike is the motors spinning, chain on or chain off. And like KiM mentioned, you can always go to a belt if your ears are that sensative.

 

[liveforphysics]

Yeh the noise doesn't bother me as a mater of fact I want some noise so I don't get shot in the back country. I want to build a real Motocross electric bike but I think I need to find an engineer that wants my help designing a good motor. I can pull wheelies on demand on my crf250r at any speed it tops out around 70-80mph As long as I have performance and reliability like it has I will be happy.

We are both looking for the same thing. I check out everything I hear about, and they all seem to ultimately be girly crap.

I'm getting to the point that I'm thinking about making my own motors. No expense spared. Super thin laminations made of the best magnet steel alloy. Wrapped by the best motor winding guys in the RC hobby with the best wire. Nb-50 magnets that sit flushed into deep recessed retention groves in the outer rotor. Giant absurdly sized bearings, maybe ceramic even, or the best steel bearings money can buy. And a stator core with dimensions like 8"x8", so you can hit the thing with a house and not worry about it. Hit it with 1000amps at 100v bursts and it will suck it up and ask for more.

 

[AussieJester]

Me too but I don't want hub motors for it I will make a chain drive! But I cant find a motor I want to do it with And I think I will need around 20ah at 24s lipo or more but I can hide that well in a stock bike frame.

oooh i dunno...theres a battery box on this page that might do it :: wink ::

Have you considered the Agni motors? Maybe dual or triple rc motors even to save weight...?
i would 110% prefer a chain setup over hub for off road.. noise isn't an issue in fact the more the
better as far as im concerned ...Best of luck getting the performance your chasing TBH i dont
like your chances... i would prefer a Honda crf250r anyday of the week

Looks like 'ol Methy has turned to "the dark side" Luke... :: sigh :: What a sad day
it is was when I discovered my GanGTSa Mentor had soft cocked it and went back to hub motors...
Perhaps we can all pitch in and buy him a nice pink frock to wear
when he goes riding now hehehe... Just teasing Patrick, you is still bad ass ...even with hubz

KiM

EDIT: p.s DO IT DO IT DO IT Luke!!!

 

[liveforphysics]

i would prefer a Honda crf250r anyday of the week

soft cocked it and went back to hub motors...
Perhaps we can all pitch in and buy him a nice pink frock to wear
when he goes riding now

He already has a pink frock collection, each one is labled for the day of the week.

I agreed with everything except that letter "F" in the CRF250R... Surely that was a typo, and you meant to say CR250R. 2-stroke for life! 4-strokes on dirt are for the pink-frock crowd. I want to fear for my life everytime the powerband hits, and you just don't get that from bikes with the letter "F" in the name.

 

[AussieJester]

He already has a pink frock collection, each one is labled for the day of the week.

I agreed with everything except that letter "F" in the CRF250R... Surely that was a typo, and you meant to say CR250R. 2-stroke for life! 4-strokes on dirt are for the pink-frock crowd. I want to fear for my life everytime the powerband hits, and you just don't get that from bikes with the letter "F" in the name.

Yes granted the 250 two stroke would have more poke, but the CRF would still be a better bike than any electric available at
this time IMO. No e-MotoX bike has the range to compare while riding it with throttle fun factor set too HIGH...
Maybe if your into soft cock riding ie. 2-3 laps around the back block and call it a day an e-motox bike would suffice but
Unless someone knows something i don't? there isn't a e-motox bike that can be ridden flat out for a couple of hours
topped off in 30 seconds with "juice" and go again hard for another few hours? no?...didn't think so...In time maybe.
Till then TWO STROKERs FTMFW

Poor Methods, you don't half give it too him you two would be hilarious to watch argue IRL...

KiM

 

[ZapPat]

Excessive testosterone problems, guys? All the references to being "pink", "soft cocked" reminds me of the good old school days when I had to travel over an hour on the bus each day with the bunch of local hillbillies... :lol:

And of course you guys best of all know that EVs can't *yet* compete in trip range with those stinkers we've been perfecting for about 100 years. Around here there are *lots* of jocks that love the noise and even smell of those two-strokes (in fact you're considered weird by many if you don't). My neighbour's kid right across the road rides around in circles in the field for hours each summer, and sounds much like a fly caught in a spider web. Such a great legacy that his 'pa taught him to love...