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deltabravo

Spokane, WA

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Posted: 04/07/20 06:18am Link  |  Quote  |  Print  |  Notify Moderator

Twistedlarch wrote:

jdc1 wrote:

https://www.amazon.com/b/ref=DEX_NR_Covid?node=9433645011&pd_rd_w=YQLam&pf_rd_p=8ba1fd08-7860-44d7-b85e-7ca4028710d8&pf_rd_r=E67ZFDXT7ENHYZ181VEW&pd_rd_r=08f4818a-763a-4b36-80a4-a74e508c7f48&pd_rd_wg=FzCAv

This link takes me to Amazon but doesn't show anything.


Ditto. That's what I call "Epic Link Failure"


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pianotuna

Regina, SK, Canada

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Posted: 04/07/20 08:50am Link  |  Quote  |  Print  |  Notify Moderator

babock wrote:

pianotuna wrote:

babock,

It would be good to provide a link to back up statements.

I do prefer MPPT myself.
Back up statements? You mean the output of a PWM vs MPPT?

Which part do you not understand?


babock,

You have offered an opinion.

Folks want to see studies that prove MPPT works better than PWM.

An ideal study would compare the payback time for the difference in cost.

For example, in 2005 my system panels cost was $5.50 per watt. Going to MPPT saved on the cost of the system, making a zero price difference between MPPT and PWM, at $1700.00. In 1990 I had a 30 watt system--which cost about $1700.00

Since then the price of panels has dropped precipitously but charge controllers not so much. The lowest price was, before artificial tariffs were introduced $0.36 cents per watt, retail.

That makes it cheaper to add another panel rather than switching to an MPPT controller, provided there is room on the roof.

So, today, my system would have a fully featured PWM controller rather than MPPT, if cost were the only criterion. But cost is not the only factor, and the price of a large capacity controller is a one time cost.

If the roof has no more room left, then MPPT to gather every erg of power may make sense.

My dream system would have remote actuators for tilt, and an MPPT controller with a system input voltage of at least 70 volts, and 2000 watts of panels.

So I suggested you to present a study that proves your opinion.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

babock

Los Angeles, CA

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Posted: 04/07/20 08:16pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:


babock,

You have offered an opinion.

Folks want to see studies that prove MPPT works better than PWM.

An ideal study would compare the payback time for the difference in cost.

For example, in 2005 my system panels cost was $5.50 per watt. Going to MPPT saved on the cost of the system, making a zero price difference between MPPT and PWM, at $1700.00. In 1990 I had a 30 watt system--which cost about $1700.00

Since then the price of panels has dropped precipitously but charge controllers not so much. The lowest price was, before artificial tariffs were introduced $0.36 cents per watt, retail.

That makes it cheaper to add another panel rather than switching to an MPPT controller, provided there is room on the roof.

So, today, my system would have a fully featured PWM controller rather than MPPT, if cost were the only criterion. But cost is not the only factor, and the price of a large capacity controller is a one time cost.

If the roof has no more room left, then MPPT to gather every erg of power may make sense.

My dream system would have remote actuators for tilt, and an MPPT controller with a system input voltage of at least 70 volts, and 2000 watts of panels.

So I suggested you to present a study that proves your opinion.
All I did was give an example of performance for a PWM vs MPPT for an example 100W 20V solar panel. I didn't put a cost comparison..just a technical operating difference. Those were factual numbers....not an opinion. You have to decide for yourself if it's worth the cost difference....which in my opinion is a pretty low difference.


If you don't understand how PWM and MPPT work, I really can't help you with that. A PWM's max output current is the max current of the panel. An MPPT is a DC to DC converter which can convert 98% of the power collected. For example, 100W/14V x.98 = 7A. The PWM 100W will output 5A if it is a 20V panel. Can't make it any simpler than that. No links needed...it's just the math. If you can't figure out the simple math I just posted, not sure what to say to you.

* This post was edited 04/07/20 08:27pm by babock *

babock

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Posted: 04/07/20 08:30pm Link  |  Quote  |  Print  |  Notify Moderator

StirCrazy wrote:

pianotuna wrote:

babock,

It would be good to provide a link to back up statements.

I do prefer MPPT myself.


in theory what he said is right, but in real world with both setups ideal I would probably expect a 1 amp difference.

Steve
All depends on the specs of the panels. The lower the voltage of the panel used, the less difference there is.

StirCrazy

Kamloops, BC, Canada

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Posted: 04/08/20 05:44am Link  |  Quote  |  Print  |  Notify Moderator

babock wrote:

StirCrazy wrote:

pianotuna wrote:

babock,

It would be good to provide a link to back up statements.

I do prefer MPPT myself.


in theory what he said is right, but in real world with both setups ideal I would probably expect a 1 amp difference.

Steve
All depends on the specs of the panels. The lower the voltage of the panel used, the less difference there is.


yup, and the higher the better, well when your talking 24v systems you need a MPPT anyways so its a mute point.

Steve


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pianotuna

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Posted: 04/08/20 09:12am Link  |  Quote  |  Print  |  Notify Moderator

babock wrote:

All I did was give an example of performance for a PWM vs MPPT for an example 100W 20V solar panel. I didn't put a cost comparison..just a technical operating difference. Those were factual numbers....not an opinion.


And all I'm suggesting is that you post a link to that testing and those numbers.

bpounds

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Posted: 04/08/20 09:40am Link  |  Quote  |  Print  |  Notify Moderator

We shouldn't even be having the PWM vs MPPT discussions these days. The info is out there for anyone who wants to even briefly study the question.

Price difference is so small now that PWM only makes sense for the smallest system, and when there is no chance for future increase.

You might even save most of the cost difference by using smaller conductors and higher voltage if there are more than 2 panels in the array. And who doesn't want as much energy as possible out of their investment?


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babock

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Posted: 04/08/20 03:06pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

babock wrote:

All I did was give an example of performance for a PWM vs MPPT for an example 100W 20V solar panel. I didn't put a cost comparison..just a technical operating difference. Those were factual numbers....not an opinion.


And all I'm suggesting is that you post a link to that testing and those numbers.
LOL...if you don't understand the math how an MPPT or a PWM work, there are a lot of sites that will explain it to you. I couldn't explain it any simpler. BTW EE here. I have done designs using both methods of controlling voltages/currents for years. It's not something new.

babock

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Posted: 04/08/20 03:08pm Link  |  Quote  |  Print  |  Notify Moderator

bpounds wrote:

We shouldn't even be having the PWM vs MPPT discussions these days. The info is out there for anyone who wants to even briefly study the question.

Price difference is so small now that PWM only makes sense for the smallest system, and when there is no chance for future increase.

You might even save most of the cost difference by using smaller conductors and higher voltage if there are more than 2 panels in the array. And who doesn't want as much energy as possible out of their investment?
Exactly. The only time I would buy a PWM controller, which I just did, was for a simple small wattage panel to keep my boat battery topped off while it is sitting at my dock.

pianotuna

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Posted: 04/08/20 06:03pm Link  |  Quote  |  Print  |  Notify Moderator

babock wrote:

pianotuna wrote:

babock wrote:

All I did was give an example of performance for a PWM vs MPPT for an example 100W 20V solar panel. I didn't put a cost comparison..just a technical operating difference. Those were factual numbers....not an opinion.


And all I'm suggesting is that you post a link to that testing and those numbers.
LOL...if you don't understand the math how an MPPT or a PWM work, there are a lot of sites that will explain it to you. I couldn't explain it any simpler. BTW EE here. I have done designs using both methods of controlling voltages/currents for years. It's not something new.


Let's see a link.

I'm perfectly aware of the differences between MPPT and PWM.

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