MadTechNutter
Well-known member
>>> continuation from a discussion on the Lindqvist thread:
First of all there is no "peak current" involved with these type of PMW speed regulators.
It is a 200W regulator, not a 500W one.
This is a German made legal vehicle and by law it is not permitted to produce more than 200W at any given time.
It doesn't throw you off the saddle when you apply the throttle, it has a soft start.
If you knew a little about physics, a bicycle or any object for that matter, only requires energy while accelerating which includes dealing with the force of gravity going up a slope and friction.
This friction is quite minimal on a bike, and around 50w would be sufficient to maintain 20km/h on a smooth flat road.
As I could comfortably ride for 2 hours, the average load was no more than 130W from my 260Wh battery, including hills and starts and a bit of head wind.
As for pedalling, I am old and weak, if I were to produce 400W for more than 10 seconds, I would likely faint or get a heart attack!
I was using 3 batteries wired in parallel. The sum is 9.9Ah.
At no time did the motor exceed 280W because that is how the ESC is built by design.
Internally current peaks may be higher but this is for a tiny fraction of a second.
For a PWM brushed controller running at 10kHz this would be 0.1 milliseconds !
These peaks are covered and smoothed internally by low ESR capacitors. When the current sensor detects that the maximum allowed current is exceeded the regulator switches back the duty cycle.
If you lock up the wheel you can actually see the voltage rise a bit again.
The battery never sees a real mean square current that exceeds what the ESC is rated for and in this case it is about 9A (with a but of leeway) and you can cheat out a little extra power by raising the voltage a little.
Brushless ESCs for bikes and scooters are also PWM regulators that additionally vary the frequency, are usually 3 phase but behave similar.
I am currently designing/building a 4WD electric ride-on/mini tractor, essentially an EV, fully drive-by-wire including steering.
There are 4 brushless hub motors rated for 400W. Two of them I ordered with the dedicated speed controllers and they didn't serve the purpose for the exact reason you are questioning.
They would limit the current to only 6.5A, this is for a 36V system, so only 230W.
That is all I got even if I locked up the wheels but then it shuts down.
This is evidence that even cheap Chinese speed controllers fully limit the amount of energy you can take from the battery.
So I ordered 4 new 500W speed controllers(actually 6 because I need more for the slasher motors).
Now I have the power I need to pull tree logs arounds and shift a bit of earth.
When I tried to lock up one wheel it threw one side of tractor up in the air, some serious torque in these geared down hub motors, so I needed to bolt things down for more tests.
However my current sensor never showed more than 16A, no matter how I loaded it.
Oh look, 16A x 36V = 536W, just what the doctor ordered
Yes it is built out of hard wood, imagine that :mrgreen:
[/quote][/quote][/quote][/quote][/quote]Pomst said:MadTechNutter said:As for my bike it does have a 200W 24V motor that originally ran on NiCads. This 8.33A at the rated voltage.
The battery pack consisted of 3 x 3.3Ah 7s batteries = 9.9Ah.
When new and fully charged the voltage would stay above 28.5V on the hill in question. That is 9.89A, less than 1C of the pack.
Assuming I actually had a motor that was capable of 500W, 2C would be 564W and more than enough to deliver and a whole order of magnitude less than what it is rated for, unlike EV batteries.
However the motor has only 200W rated and would have been running at 282W up that hill and maintained the speed at 20km/h. Bike has a speed limiter at 23km/h, it is something legal.
After a year held at full charge (LiPos are charged up to 4.2V it would not go up faster than 9km/h, so relatively speaking it used to 'fly' up those hills like a 'rocket'.
Yes LiPos are not EV batteries we all know that.
They are nevertheless all Li-Ion batteries.
It is common knowledge that all Li-Ion batteries suffer degradation when stored at full charge.
There is a lot of science, research and empirical evidence over the last 25 years that supports the claim that Li-Ion batteries are best stored at 3.7V
There is also some evidence suggesting that keeping batteries stored at temperatures near 0˚C is beneficial.
This MIGHT also have something to do why Australian users of the car are complaining more about battery degradation than from countries with colder climates.
Secondly, you have you calculations way off and it proves my point on experience of batteries.
The voltage of the cell drops under load, depending on the load the cell drops differently when the current increases. My estimates of the load on your cells are based on about 4 packs of hand built bicycle batteries and a dozen of motors with anything from custom controllers to Chinese ones.
A 200w motor is 200w continuously not peak, it could easily peak 600w or more if the controller allows it. Like
I said, it depends on your definition of "rocket", 200w is nothing. Just pedaling gives you 300-400w power.
Assuming you didn't, if you had a proper controller like a Cycle Analyst V3 you would see what I am talking about.
What does 3x 3.3Ah 7S mean? Is it a 7S pack or a 7S3P pack? Because the two are vastly different and effect the C rating dramatically. Irrespective of which, this experiences is not relatable to the cells in an EV pack.
My experience in batteries is not only gathering batteries and looking at them.
I build stuff from them and reverse engineer the BMS systems on the EV packs.
As I stated, EV batteries do not degrade much at all over a 10 year period because of their nature and the strict limits in the BMS.
RC batteries are like a dragster motor, they run hot and fast but die quickly.
The two are not comparable in any way shape or form.
First of all there is no "peak current" involved with these type of PMW speed regulators.
It is a 200W regulator, not a 500W one.
This is a German made legal vehicle and by law it is not permitted to produce more than 200W at any given time.
It doesn't throw you off the saddle when you apply the throttle, it has a soft start.
If you knew a little about physics, a bicycle or any object for that matter, only requires energy while accelerating which includes dealing with the force of gravity going up a slope and friction.
This friction is quite minimal on a bike, and around 50w would be sufficient to maintain 20km/h on a smooth flat road.
As I could comfortably ride for 2 hours, the average load was no more than 130W from my 260Wh battery, including hills and starts and a bit of head wind.
As for pedalling, I am old and weak, if I were to produce 400W for more than 10 seconds, I would likely faint or get a heart attack!
I was using 3 batteries wired in parallel. The sum is 9.9Ah.
At no time did the motor exceed 280W because that is how the ESC is built by design.
Internally current peaks may be higher but this is for a tiny fraction of a second.
For a PWM brushed controller running at 10kHz this would be 0.1 milliseconds !
These peaks are covered and smoothed internally by low ESR capacitors. When the current sensor detects that the maximum allowed current is exceeded the regulator switches back the duty cycle.
If you lock up the wheel you can actually see the voltage rise a bit again.
The battery never sees a real mean square current that exceeds what the ESC is rated for and in this case it is about 9A (with a but of leeway) and you can cheat out a little extra power by raising the voltage a little.
Brushless ESCs for bikes and scooters are also PWM regulators that additionally vary the frequency, are usually 3 phase but behave similar.
I am currently designing/building a 4WD electric ride-on/mini tractor, essentially an EV, fully drive-by-wire including steering.
There are 4 brushless hub motors rated for 400W. Two of them I ordered with the dedicated speed controllers and they didn't serve the purpose for the exact reason you are questioning.
They would limit the current to only 6.5A, this is for a 36V system, so only 230W.
That is all I got even if I locked up the wheels but then it shuts down.
This is evidence that even cheap Chinese speed controllers fully limit the amount of energy you can take from the battery.
So I ordered 4 new 500W speed controllers(actually 6 because I need more for the slasher motors).
Now I have the power I need to pull tree logs arounds and shift a bit of earth.
When I tried to lock up one wheel it threw one side of tractor up in the air, some serious torque in these geared down hub motors, so I needed to bolt things down for more tests.
However my current sensor never showed more than 16A, no matter how I loaded it.
Oh look, 16A x 36V = 536W, just what the doctor ordered
Yes it is built out of hard wood, imagine that :mrgreen: