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Why is mppt better than pwm?

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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Every current SCC modulates using PWM. The modulation is to 99,9% done from microcontrollers.
Your "numbers of transistors" is here not a key to differentiate.
 
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...

:ROFLMAO:
You have got no clue... just no clue.
For someone that has no clue, I seem to muddle along quite well designing all my own equipment that includes solar controllers and rather unique multi kilowatt pure sine wave inverter. Suggest you google Warpverter.
What have you ever designed ?
 
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.

And no (other) FETs to make the square wave, right?
So how does it Modulate the Pulse Width if it has no Pulse to Modulate?

Look, OK, I give up.
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I keep trying, but it looks hard...

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:
iu


They usually sit on the back, yes.
The one you have uses the series topology (as mention on the thread I gave the link too earlier), not the typical buck converter type that needs inductor, which as you can see bunch of power MOSFET's mounted on back side of the PCB and press against the heatsink (back cover of the unit)
'The PV array is connected to the battery through a series or parallel (called Shunt) connected MOSFET Switch'
They use this topology on these low cost PWM SCC.
I.E. Samlex SCC.

 
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And, decided on my answer.
Answer: blue
The blue one$$$$$ are made on Mondays. i prefer the green one$$ from Thursday,
Avoid Fridays generic colored one$ when they are down to the bottom of the parts bin and the workers are jaded.
 
I would avoid Monday since they may have hang over from the heavy partying on the weekend.
 
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Sorry, but that is technically quite wrong, you have been taken in by sales mumbo jumbo.

Oh by the way, I am a retired power electronics design engineer. I will go into discussing the electronics as deeply as you wish, its what I do.
Before retirement I used to design this type of equipment for mass production and commercial sale.

Both use the classic buck converter circuit. This chops up the incoming dc voltage into discrete pulses of varying width.
The resulting rectangular waveform is then averaged in a series choke to produce a steady dc output of lower voltage and higher current.
The technique is commonly called pulse width modulation.

There is no such thing as a dc transformer, transformers use magnetic coupling of two or more windings, and can only work with ac.

However, clever sales and marketing people like to invent technical terms that makes their products stand out.
The idea that adding different software to control it, makes the product much larger and heavier is just laughable.

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.
From: https://www.leonics.com/support/article2_14j/articles2_14j_en.php

"MPPT is DC to DC converter which operates by taking DC input from PV module, changing it to AC and converting it back to a different DC voltage and current to exactly match the PV module to the battery."

The hardware is NOT identical. This is why legit MPPT controllers are larger and/or heavier than PWM controllers.

By the way, I have a degree in engineering too.
 
Interesting timing - I just finished a test of 30A MPPT & a 30A PWM close to their rated capacities - five 100 Watt panels in series for the MPPT & parallel for the PWM. The MPPT delivered 28.5 Amps to a 12V battery (battery voltage 13.5V) and the PWM delivered 30-31 Amps. This result is what I expected, but counter to what most people believe. There are several factors that determine the final current/power delivered to the batteries. I'll do my best to explain them below, but will not get into a pi**ing contest with those that argue.

Test conditions: SF Bay area, clear & sunny sky ambient temp 74F/24C. Sun nearly overhead. insolation 886 W/m2. Panel temperature 55-58C with a handheld IR temp gauge.

Equipment - five 100 Watt Newpowa panels, Interstate flooded cell battery partially discharged, Epever 30A/100V MPPT, 30A Bogart PWM, Fluke clamp-on & regular multimeters.

factors affecting a MPPT & PWM controllers' performance:
1) Temperature effect on the panel's voltage/power - Newpowa's derating factor is 0.5%/C. For my tests, this amounts (55-25)*0.5 or 15%. This alone hurts a MPPT controller's performance. A PWM controller is somewhat immune to this as long as the voltage at its input is higher than the battery voltage. A PWM sucks the Isc from a panel and Isc is typically 8-12% higher than the Imp. I suspect that in my tests, the bogart PWM could have delivered a little more, since its overcurrent LED was flashing.

2) Loss of DC-DC conversion efficiency. The 98% conversion efficiency typically quoted in product brochures is the peak efficiency.
At the rated max current, the efficiency drops off to 90-95%. Most significant contributor is the I2R power loss on the current switching MOSFETs & the inductor(s).
Additionally, the input to output voltage differential has a effect on the efficiency; higher the differential, lower the efficiency. Five panels in series takes the input voltage 70-80V range, with a corresponding efficiency hit. A MPPT is at its best efficiency when at the midpoint of its current specs (15A in this case) and about 2X input output voltage (2 panels in series).

The Epever was taking in about 425-430 Watts & delivering 395Watts or about 8% loss.

I ran these tests for someone who was interested in it. I may repeat them with more variations (2S2p for the MPPT) LFP battery, etc. Did not have a chance to video them as I was working alone.

Moral of the story: PWM controller can do better than MPPT's under some conditions & vice-versa. Consider your personal case, instead of looking for a one size fits all response.

editing to attach a typical buck converter efficiency plot to illustrate the comment I make above.
 

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There's a lot of misconception expressed in this thread as to what MPPT & PWM controllers are.

MPPT controllers do use a PWM circuit block but not in the simpler way that a PWM controller uses. The PWM circuit in an MPPT controller changes the duty cycle of the buck converter switches, which, in turn, changes the input impedance (as seen by the panels) of the buck conversion circuit. This allows the circuit to extract power at the panels' 'sweet spot' in the voltage-current curve. A microcontroller calculates the duty cycle of the PWM signal. See the block diagram of a recent (2018) reference MPPT circuit from TI - https://www.ti.com/tool/TIDA-010042. Most MPPT controllers are similar in design.

A PWM charge controller connect the panels directly the batteries in the bulk charge phase - the switching MOSFET is on 100% of the time. During the absorb cycle, the MOSFET is actively controlled (less than 100% duty cycle) to maintain the absorb voltage programmed in.
 

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Interesting timing - I just finished a test of 30A MPPT & a 30A PWM close to their rated capacities - five 100 Watt panels in series for the MPPT & parallel for the PWM. The MPPT delivered 28.5 Amps to a 12V battery (battery voltage 13.5V) and the PWM delivered 30-31 Amps. This result is what I expected, but counter to what most people believe. There are several factors that determine the final current/power delivered to the batteries. I'll do my best to explain them below, but will not get into a pi**ing contest with those that argue.

Test conditions: SF Bay area, clear & sunny sky ambient temp 74F/24C. Sun nearly overhead. insolation 886 W/m2. Panel temperature 55-58C with a handheld IR temp gauge.

Equipment - five 100 Watt Newpowa panels, Interstate flooded cell battery partially discharged, Epever 30A/100V MPPT, 30A Bogart PWM, Fluke clamp-on & regular multimeters.

factors affecting a MPPT & PWM controllers' performance:
1) Temperature effect on the panel's voltage/power - Newpowa's derating factor is 0.5%/C. For my tests, this amounts (55-25)*0.5 or 15%. This alone hurts a MPPT controller's performance. A PWM controller is somewhat immune to this as long as the voltage at its input is higher than the battery voltage. A PWM sucks the Isc from a panel and Isc is typically 8-12% higher than the Imp. I suspect that in my tests, the bogart PWM could have delivered a little more, since its overcurrent LED was flashing.

2) Loss of DC-DC conversion efficiency. The 98% conversion efficiency typically quoted in product brochures is the peak efficiency.
At the rated max current, the efficiency drops off to 90-95%. Most significant contributor is the I2R power loss on the current switching MOSFETs & the inductor(s).
Additionally, the input to output voltage differential has a effect on the efficiency; higher the differential, lower the efficiency. Five panels in series takes the input voltage 70-80V range, with a corresponding efficiency hit. A MPPT is at its best efficiency when at the midpoint of its current specs (15A in this case) and about 2X input voltage (2 panels in series).

The Epever was taking in about 425-430 Watts & delivering 395Watts or about 8% loss.

I ran these tests for someone who was interested in it. I may repeat them with more variations (2S2p for the MPPT) LFP battery, etc. Did not have a chance to video them as I was working alone.

Moral of the story: PWM controller can do better than MPPT's under some conditions & vice-versa. Consider your personal case, instead of looking for a one size fits all response.

editing to attach a typical buck converter efficiency plot to illustrate the comment I make above.
So what configuration of the 5 panels you used when testing the PWM SCC? all 5 in parallel?
What is the Is and Imp of the panels?
 
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That is a great article written in 2000! You should check out some of their newer ones too.
The topology is not changed in the cheap PWM SCC with USB ports selling on Amz and Ebay, the article is just a ref, for basic learning.
 
Are you saying that with MPPT your 5 panels in parallel will under perform the PWM?

Or, are you simply showing a pathological case where MPPT can be mis-configured to perform worse than PWM?
 
From: https://www.leonics.com/support/article2_14j/articles2_14j_en.php

"MPPT is DC to DC converter which operates by taking DC input from PV module, changing it to AC and converting it back to a different DC voltage and current to exactly match the PV module to the battery."

The hardware is NOT identical. This is why legit MPPT controllers are larger and/or heavier than PWM controllers.

By the way, I have a degree in engineering too.
Draw me a very basic functional circuit diagram of just the power conversion stage of each, with an explanation of how each works, and explain the differences.
Should be trivial for a qualified electronic engineer.
 
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Draw me a circuit diagram of both with an explanation of how each works, and explain the differences.
Should be trivial for a qualified engineer.
Do you have the schematics of the PWM SCC and the MPPT SCC that you deseign?
 
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