Just bought a used Woosh Fat Boy

[WheezyRider]

as I said before, if you build a bike for 28mph, you are better off with a direct drive. You won't blow up the motor in 1000 miles.
Let's recap, overvolting means you stick a 48V battery on a 36V bikes.
Let those who did so to their bikes come say how many miles they've done with their overvolted bike here.
to play with their kit for 5 minutes is just that, playing, never a practical proposition.

I don't think anyone here is talking about doing 28 mph, just wanting something giving 15.5 mph up a hill without struggling.

As I said, over volting still means the motor cuts out at 15.5 mph if the wheel size is set up properly on the LCD.

No problems with my motors so far when over volted. I'll keep people here updated...

I'm sure others will be able to replicate what other people on the web have done, ie many thousands of miles in an over voltage condition without problems.

 

[vfr400]

Let those who did so to their bikes come say how many miles they've done with their overvolted bike here.

My 36v Q128c motor has done 4000 miles so far at 48v. As I already said, motors don't care about voltage. It's current that burns them. You're more likely to burn something at 36v and 20 amps than you are with 48v and 15 amps. The power is the same, and so is the torque.

 

[Woosh]

do you use a 48V controller?
Can you compare the risk of frying the electronics between your controller and the 17AH Lishui HL controller on the OP's Rio FB?
BTW, how many of those 4000 miles that you ride at over 22mph* that justify the overvolting?

* anything below 22mph does not need overvolting

 

[vfr400]

BTW, how many of those 4000 miles that you ride at over 22mph* that justify the overvolting?

* anything below 22mph does not need overvolting

You're incorrect. I use 48v to get more torque at lower current, not for increased speed. I run a 14A controller, which gives me more than enough power for the steepest hills. I keep telling you that you should change to 48v, but you don't listen.

 

[Woosh]

it's you who misread the situation.
The Bafang G06 motor is robust enough, it's not a big problem to put 1kW though it for 10 minutes to climb a hill. I have said so many times. It's not kind to the motor but it'll live. It's the rest of the electronics.
You need a proper 48V controller and LCD. You can't use the existing Lishui HL controller and the C200 LCD.
If you use KT kit, you need a new wiring loom.
I have explained all this yesterday. To convert the Rio FB to 48V, you need a budget of around £400.
The real issue is those who want to use it as a motorbike, running it at maximum speed to save time. Overvolting gives them a normal looking bike with a brand and an EN15194 sticker while breaking law.
And add to that, my friend helps him to do that to me.

 

[WheezyRider]

it's you who misread the situation.
The Bafang G06 motor is robust enough, it's not a big problem to put 1kW though it for 10 minutes to climb a hill. I have said so many times. It's not kind to the motor but it'll live. It's the rest of the electronics.
You need a proper 48V controller and LCD. You can't use the existing Lishui HL controller and the C200 LCD.
If you use KT kit, you need a new wiring loom.
I have explained all this yesterday. To convert the Rio FB to 48V, you need a budget of around £400.
The real issue is those who want to use it as a motorbike, running it at maximum speed to save time. Overvolting gives them a normal looking bike with a brand and an EN15194 sticker while breaking law.
And add to that, my friend helps him to do that to me.

I get your concerns about your brand etc, which is fine for selling your products. But just because someone over volts their bike does not mean they want to break the law. That only happens if the user deliberately misrepresents the wheel diameter in the LCD set up.

As VFR said, it's much better to get that 1kW from high volts/low amps than the other way around. Heat is your enemy, which is proportional to the current squared.

 

[vfr400]

it's you who misread the situation.
The Bafang G06 motor is robust enough, it's not a big problem to put 1kW though it for 10 minutes to climb a hill. I have said so many times. It's not kind to the motor but it'll live. It's the rest of the electronics.
You need a proper 48V controller and LCD. You can't use the existing Lishui HL controller and the C200 LCD.
If you use KT kit, you need a new wiring loom.
I have explained all this yesterday. To convert the Rio FB to 48V, you need a budget of around £400.
The real issue is those who want to use it as a motorbike, running it at maximum speed to save time. Overvolting gives them a normal looking bike with a brand and an EN15194 sticker while breaking law.
And add to that, my friend helps him to do that to me.

That's what I said in post #3!

 

[Woosh]

wheezy, if a customer calls us about a bike, we always, always ask for his/her weight and height and where he/she lives. We make bikes with 40NM motors (85SX on the Faro) to Bafang BPM 65NM motor on the Big Bears. Horses for courses, the bike must be able to do the job.
There is no need for more than 36V 20A controller to make a pedal assist bike. Only those who want to go beyond 25mph need more than that.
On exceptional circumstances, too tall or 30st, I suggest our 48V kits.
It's not I don't understand people have different neeeds, I cannot sell a bike or a kit to someone who tells me upfront he is going to use the bike 'off road'. My reply to them has always been that we don't make off road bikes.

 

[WheezyRider]

wheezy, if a customer calls us about a bike, we always, always ask for his/her weight and height and where he/she lives. We make bikes with 40NM motors (85SX on the Faro) to Bafang BPM 65NM motor on the Big Bears. Horses for courses, the bike must be able to do the job.
There is no need for more than 36V 20A controller to make a pedal assist bike. Only those who want to go beyond 25mph needs more than that.

The thing is, I would not want to put 20A into a "250W" motor. It's a bad idea. Much better to use 15A and a higher voltage to get the peak power needed for hill climbing etc. With voltage adjusted accordingly, that extra 5A means almost double the heating of the motor for the same power output.

 

[Woosh]

wheezy, that's not correct. The phase of the current and voltage in/on the coils are at 90 degrees angle current versus voltage. The coils are not resistors unless when it stalls, then the controlller will stop sending power to it.
The amount of heat wasted through the motor is shown as = 1- yield. So, low yield = more wasted heat. The yield changes with the RPM and Kv, a motor constant. The voltage has no real effect on the motor itself, as I said, the yield changes with the RPM. You want it optimal at 200 RPM for full size bikes. The motor is wound so that you get optimal yield for the voltage you are going to use.
You are going to shed more heat proportionally unless you ride always at the optimal RPM.
When you overvolt one of my motors, you move the optimal RPM to 260. So instead of enjoying best speed at 15mph, it's going to be 20mph.
I know it's fine for some, but not what I am supposed to do.

 

[Sturmey]

I think there is some things people are forgetting.
Firstly, to get more torque, (other than changing gearing) you always have to put more current through the motor, as torque is proportional to current.

Battery current is not the same as phase (motor) current.

The extra torque that comes from overvolting is caused by extra motor current over and above the battery current, as motor system steps down voltage and steps up current. (acts like buck converter)
This can be demonstrated below with motor simulator, as motor current of 20.5 amp at 36v X 18.2amp controller is same as 48v X 14 amp, both representing a 30% increase in normal 36v X 14amp controller.
There is no magic way (in this case) of getting more torque without more heat in motor, without changing gearing. e.g. Volt up,Gear down.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

www.ebikes.ca

 

[Woosh]

you need to think of electricity like waves, the voltage at the storage capacitor is not same as battery's voltage. It is wavy, although connected to the battery with two short fat wires, black and red.
the increase in motor current that is needed for more torque is partially supplied by the 2.2mF storage capacitor.
Higher voltage increases the energy stored, thus gives higher discharge current through the coils.
Oscillations caused by the back EMF in an overvolted motor create also 30%-50% higher voltages when riding at high speed because the magnets in an overvolted motor are working at over saturated state. When the increase current cannot create any more magnetic flux, its wave is reflected back like a sea wave hitting a rock. Same thing as regen, spontaneous turbulent voltage is much higher than your battery's voltage.
The thing you should worry about is the width of the tracks on your controller's PCB. Wave travels only on the surface of the conductor. Higher wave creates more heat on the tracks.
If your storage capacitor is not good enough, the back EMF may kill this capacitor at set fire to the controller.
Rule of thumb: lower voltage = better reliability.

 

[WheezyRider]

wheezy, that's not correct. The phase of the current and voltage in/on the coils are at 90 degrees angle current versus voltage. The coils are not resistors unless when it stalls, then the controlller will stop sending power to it.
The amount of heat wasted through the motor is shown as = 1- yield. So, low yield = more wasted heat. The yield changes with the RPM and Kv, a motor constant. The voltage has no real effect on the motor itself, as I said, the yield changes with the RPM. You want it optimal at 200 RPM for full size bikes. The motor is wound so that you get optimal yield for the voltage you are going to use.
You are going to shed more heat proportionally unless you ride always at the optimal RPM.
When you overvolt one of my motors, you move the optimal RPM to 260. So instead of enjoying best speed at 15mph, it's going to be 20mph.
I know it's fine for some, but not what I am supposed to do.

I should have made myself clearer. I'm mainly talking about near stall conditions, eg starting off, slowly climbing a steep hill, heading into a strong wind.

 

[WheezyRider]

I think there is some things people are forgetting.
Firstly, to get more torque, (other than changing gearing) you always have to put more current through the motor, as torque is proportional to current.

Battery current is not the same as phase (motor) current.

The extra torque that comes from overvolting is caused by extra motor current over and above the battery current, as motor system steps down voltage and steps up current. (acts like buck converter)
This can be demonstrated below with motor simulator, as motor current of 20.5 amp at 36v X 18.2amp controller is same as 48v X 14 amp, both representing a 30% increase in normal 36v X 14amp controller.
There is no magic way (in this case) of getting more torque without more heat in motor, without changing gearing. e.g. Volt up,Gear down.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

www.ebikes.ca

Can you explain how the controller is acting like a Buck converter? To do this requires a significantly sized inductor, which I have not seen in any controller I have taken apart.

There is a small Buck converter for the control electronics, but not as far as I am aware for the main drive.

I would like to see an oscilloscope trace of controller output, demonstrating that the controller is actively reducing voltage (other than being unable to supply enough current and having it's voltage pulled down).

 

[WheezyRider]

you need to think of electricity like waves, the voltage at the storage capacitor is not same as battery's voltage. It is wavy, although connected to the battery with two short fat wires, black and red.
the increase in motor current that is needed for more torque is partially supplied by the 2.2mF storage capacitor.
Higher voltage increases the energy stored, thus gives higher discharge current through the coils.
Oscillations caused by the back EMF in an overvolted motor create also 30%-50% higher voltages when riding at high speed because the magnets in an overvolted motor are working at over saturated state. When the increase current cannot create any more magnetic flux, its wave is reflected back like a sea wave hitting a rock. Same thing as regen, spontaneous turbulent voltage is much higher than your battery's voltage.
The thing you should worry about is the width of the tracks on your controller's PCB. Wave travels only on the surface of the conductor. Higher wave creates more heat on the tracks.
If your storage capacitor is not good enough, the back EMF may kill this capacitor at set fire to the controller.
Rule of thumb: lower voltage = better reliability.

The 2,200 microF capacitor is for filtering and smoothing, not for driving the motor when output from the controller drops. The energy in a capacitor is 0.5*C*V squared. At 40V, this is less than 2 Joules of energy, that's not going to drive a "250W" motor for very long!

These days there is not much point for controller manufacturers to make 36V specific systems and 48V specific systems. It's much cheaper to have one PCB, one production line, one source of standard conponents and just solder a bridge in for the desired LCV setting. So in most cases these days, "36V" controllers have no problem handling 48V and this is well within their spec and not stressing them significantly.

In terms of shorter life, (which is debatable) I'd much rather increase the life of the motor than the controller as it's much easier and cheaper to replace the controller.

 

[Woosh]

At 40V, this is less than 2 Joules of energy, that's not going to drive a "250W" motor for very long!

you got it wrong. The pulses going through the coils are about 22kHz-40kHz.
the pulse going through the coils lasts only about 0.04ms.

what is the power of 2J delivered in 0.04ms?

It's not the battery that can deliver that power. It's the job for the storage capacitor.

 

[WheezyRider]

I think there is some things people are forgetting.
Firstly, to get more torque, (other than changing gearing) you always have to put more current through the motor, as torque is proportional to current.

Battery current is not the same as phase (motor) current.

The extra torque that comes from overvolting is caused by extra motor current over and above the battery current, as motor system steps down voltage and steps up current. (acts like buck converter)
This can be demonstrated below with motor simulator, as motor current of 20.5 amp at 36v X 18.2amp controller is same as 48v X 14 amp, both representing a 30% increase in normal 36v X 14amp controller.
There is no magic way (in this case) of getting more torque without more heat in motor, without changing gearing. e.g. Volt up,Gear down.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

www.ebikes.ca

If voltage is irrelevant, why don't we just use 12V systems and wind our motors accordingly to spin at the right RPM? Voltage does have a role to play, it improves efficiency and reduces current demand for a given Wattage.

There seem to be a lot of people giving opinions (myself included!) without the necessary understanding of motor electronic engineering and control. I'd like to hear from someone who really understands these things and has studied this matter in depth. Otherwise this is just going to generate more heat than light.

As time goes on, I will make measurements, keep experimenting etc and gain more knowledge. But in the mean time I will continue to use my bike at higher voltages and enjoy the better ride that it gives.

 

[Woosh]

If voltage is irrelevant, why don't we just use 12V systems and wind our motors accordingly to spin at the right RPM? Voltage does have a role to play, it improves efficiency and reduces current demand for a given Wattage.

There seem to be a lot of people giving opinions (myself included!) without the necessary understanding of motor electronic engineering and control. I'd like to hear from someone who really understands these things and has studied this matter in depth. Otherwise this is just going to generate more heat than light.

As time goes on, I will make measurements, keep experimenting etc and gain more knowledge. But in the mean time I will continue to use my bike at higher voltages and enjoy the better ride that it gives.

high voltage is important to reduce transport loss but bad for the longevity of the components and incurs bigger loss through EM radiations when you use in an oscillating circuitry like e-bike motor.
I only use higher 48V instead of 36V to reduce the stress on the battery cells.

In my days, CPUs run at 5V when I built my first computer using Motorola 6800 CPU, TTL circuits and 1kilobit static memory chips. You can't have the density of modern intel CPUs if they still runs on 5V. Less voltage gives better reliability.

 

[WheezyRider]

high voltage is important to reduce transport loss but bad for the longevity of the components and incurs bigger loss through EM radiations when you use in an oscillating circuitry like e-bike motor.
I only use higher 48V instead of 36V to reduce the stress on the battery cells.

In my days, CPUs run at 5V when I built my first computer using Motorola 6800 CPU, TTL circuits and 1kilobit static memory chips. You can't have the density of modern intel CPUs if they still runs on 5V. Less voltage gives better reliability.

This just proves my point.

Sometimes being on this forum is like listening to a load of old men sat in the corner of the pub, telling each other more and more fantastic tales. Each of the others has enough knowledge to cast doubt on what the speaker is saying, but not enough to disprove it out right...while the speaker has enough knowledge to make their story have some credence, but not enough to prove its truth out right.

It's entertaining but right now I need to get on with some work!

 

[Woosh]

you still have not answered my question:
you said, "At 40V, this is less than 2 Joules of energy, that's not going to drive a "250W" motor for very long! "

My question is:

so knowing that the pulse width is 0.04ms, what is the power delivered through the coils?

Answering this question may lead you to understand the motor better than I could explain.