Why is mppt better than pwm?

[Warpspeed]

Wikipedia, pulse width modulation:
https://en.wikipedia.org/wiki/Pulse-width_modulation

The middle of the first paragraph mentions how MPPT can be used in conjunction with PWM, click on the link for an explanation of MPPT.
An MPPT controller still always uses pulse width modulation to adjust the solar panel loading and battery voltage. Its the exact same thing, but with a software program to find and lock onto the most efficient point for bulk battery charging.

 

[rin67630]

Legit MPPT controllers use a PWM power stage with a bit if smart software that can locate and track the power peak.
PWM controllers use some less sophisticated control method, but the power conversion stage is identical.

I am sorry to disagree.
Every PWM SCC controller that I have seen had absolutely no buck converter.
Just a FET switch between panel and battery and another one between battery and load.

 

[rin67630]

Why PWM?

https://support.morningstarcorp.com/wp-content/uploads/2014/07/8.-Why-PWM1.pdf

Ist that a prospect from the 70es?

 

[Warpspeed]

Every PWM controller ?
You must only be looking at some really old junky stuff.

 

[rin67630]

Every PWM controller ?
You must only be looking at some really old junky stuff.

Tell me one PWM controller that has a buck converter. Come on !

 

[Warpspeed]

I design and build all my own equipment,so I am not familiar all that is available commercially.
And its not really possible to research this question either, as these days any circuit diagrams or real technical specifications are just not available.
All that exists are sales blurbs which tell us nothing about how it actually works.

But I might suggest that anything that uses a microcontroller, and has a digital display and is also programmable, is almost certain to have a buck converter.

 

[Don B. Cilly]

Er... do you know what PWM actually stands for?
Because if you don't convert the DC to some form of AC first, how are you going to Modulate the Pulse Width?
One transistor won't do that.

You must be referring to (really) old "hysteresis" controllers. And you probably missed the funny story about those :·)
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[rin67630]

But I might suggest that anything that uses a microcontroller, and has a digital display and is also programmable, is almost certain to have a buck converter.

Splitting hairs...
Of course they have mostly a tiny buck converter to power the microcontroller.
I was -obviously- speaking of a buck converter in the SCC power electronics

 

[rin67630]

Er... do you know what PWM actually stands for?
Because if you don't convert the DC to some form of AC first, how are you going to Modulate the Pulse Width?
One transistor won't do that.

You must be referring to (really) old "hysteresis" controllers. And you probably missed the funny story about those :·)
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That gets now completely weird !
May i suggest that you inform yourself and look at some schematics of "PWM" solar converters?

If you see e.g. this "MPPT" device, you know that it is a fake: there is just no power coil.
(beside the USB socket there is a tiny coil for the 5V buck converter) but not more.
That is a plain PWM module.

 

[Warpspeed]

I am sorry to disagree.
Every PWM SCC controller that I have seen had absolutely no buck converter.
Just a FET switch between panel and battery and another one between battery and load.

Not splitting hairs.

You said EVERY pwm controller you have seen did not use a buck converter.
That is a pretty definite statement. It may even be true.

But its highly unlikely to apply to every pwm controller on the market these days.

 

[Don B. Cilly]

So, what does it stand for? Pulse Width Modulation, right?
The graphical representation for which goes something like



Now, if you want to modulate the pulse, you must first have a pulse to modulate, right?
And how are you going to get that with one transistor?

That pcb picture you posted, you don't know what's on the other side of the board, do you? Which is closer to the heat sink?
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[rin67630]

So, what does it stand for? Pulse Width Modulation, right?
..
Now, if you want to modulate the pulse, you must first have a pulse to modulate, right?
And how are you going to get that with one transistor?

That pcb picture you posted, you don't know what's on the other side of the board, do you? Which is closer to the heat sink?
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PWM is like the steering wheel of a car: a technique to control things.
Of course a real MPPT controler also uses PWM techniques.
But what is commonly called a "PWM" controller is a device that has no kind of coil storage in the power electronics.
Ieff panel = Ieff battery. ±peanuts for own consumption.
A MPPT controller is able to get Ieff battery ≥ Ieff panel. Mostly.
Regarding you last sentence: Yes I know.
Nobody would ever be stupid enough to place the coils between the PCB and the heat sink !

 

[Don B. Cilly]

Regarding you last sentence: Yes I know.

How? Can you show us?

Nobody would ever be stupid enough to place the coils between the PCB and the heat sink !

Coils? What coils? You'd need at least a couple of (MOS-FE)transistors, though, and those would sit quite well on the heat sink.
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[Warpspeed]

Not only the inductor and mosfets, but some relatively big electrolytics too. Plus the large screw terminal blocks to connect up the battery and solar panels.

All these are kind of large parts, and rather difficult to completely hide behind a small circuit board like that.

 

[Don B. Cilly]

Well, the electrolytics are there - I count at least seven. The screw terminals are also there. The "inductor" could be that little black thing next to the USB port...
Still, what are you suggesting, that that modulates a non-existent pulse? Or that it makes one without any MOSFETs?
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[rin67630]

How? Can you show us?

I keep trying, but it looks hard...

Coils? What coils?

MPPT devices need large toroidal coils to store energy. Here completely missing so: my picture above is a dumb "PWM" controller.
A MPPT controller looks like that:

You'd need at least a couple of (MOS-FE)transistors, though, and those would sit quite well on the heat sink.-

They usually sit on the back, yes.

 

[rin67630]

The "inductor" could be that little black thing next to the USB port...

That is an inductor (a coil) indeed, but a microscopic one, just enough for the buck converter to power the microcontroler.

 

[Warpspeed]

Are you seriously suggesting those microscopic components can handle the advertised 760 watts.
That is a control board only, it has no power electronics on it.

 

[rin67630]

Are you seriously suggesting those microscopic components can handle the advertised 760 watts.

If they lie with MPPT, they will lie with the "760W" too. That value was just a theoretical 24Wx30A.
PWM controllers do handle easily 20A without much heat losses: the current just passes through the FET's...

That is a control board only, it has no power electronics on it.

You have got no clue... just no clue.

 

[Don B. Cilly]

But we were not discussing whether that was an MPPT controller (it's almost certainly not) or even the quality of it, we were discussing whether you can Modulate the Width of a Pulse without the pulse itself - which would need at least two transistors (which is probably what you call the "buck converter" part).
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