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 Post subject: Re: Self built Electric Vehicles, batteries and speed contro
PostPosted: Tue Jul 30, 2019 5:29 am 

Joined: Thu Jul 25, 2019 4:01 pm
Posts: 29
MadTechNutter wrote:
Pomst wrote:
MadTechNutter wrote:

That statement alone proves that you obviously skipped classes when you had science at school.

I weigh over 80kg and both of my LEGAL E-bikes do fine on level roads at legal speed.
Also that you now suddenly agree that speed controllers DO limit the power after elm70 mentioned it, but vehemently argue against that fact with me with several posts.

You seem to be some kind of troll with the unsubstantiated rubbish you are posting.

Either you didn't read what I wrote or you don't understand how it works.
The controllers do limit but not to 200w as they are slow and inaccurate.
This in turn allows for a high in-rush current pushing far more power to the motor then legally allowed.

Please get out the calculation for friction analysis on a deformed rubber inflated wheel on a surface with small pebbles on it.
I would love to see it.

Geez, get a grip.
If 200W can move my fat ass at 20km/h with properly inflated tyres on standard asphalt I don't have to calculate shyte.

It looks like a very simple PWM speed controller tutorial is required:

A PWM speed controller is not some basic DC switch that lets all the energy freely flow at once.
PWM stands for pulse width modulation.
That means it is constantly switching on and off, for example every 0.1milliseconds for a certain duty cycle.
A controller determines this duty cycle.
A current sensor measures the current instantly.
If this exceeds a defined value the controller can respond straight away in the next 0.1millisecond cycle with a lower duty cycle.

Any hobbyist can build such a controller with a simple PIC12F683. It costs $1.
It's A/D converter responds within 10µsec and two lines of code later I have set it's CCP (Capture Compare PWM) module to a new duty cycle

A power MOSFET can change it's on or off state within 50 nanoseconds, that is certainly not slow and can not create any inaccuracy.
It is important that they switch fast because that determines their thermal loss, not just the on-resistance.
If they would switch slow they would burn out.

I would literally have to purposely program in a delay to make such a PWM controller laggy to allow higher initial inrush current.

None of the Chinese controllers I have here go past their specified limit but some do not even reach that limit.

BTW I also have one of those iMortor wheels. I did mount it on a fairly light but standard Alu bike. Maybe that is where you might have got that 200W won't move 90kg rubbish.
The speed controller is so piss weak it doesn't reach 200W but that is by design because the included battery is tiny.
Nevertheless I have reached speeds over 25km/h with it, perfectly flat road, zero wind. Just needs a lot of patience, takes maybe a minute to get to that speed.
It sucks up hills, 12-13km/h fully charged on a light slope.

Then I found a YT video of a guy who ripped it all apart and built his own controller on top of the bike, huge, nasty with fat heatsink obviously current limit was not part of the deal.
He then displayed what 500W looks like on a 200W motor: he had wheel spin!

That's a lot of assumptions.

Good luck with your wood tractor.

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