Solar Charge Controller question

[Twistedlarch]

Here's my set up:
2018 Coachman Viking 17BHS 21'
Dual 6v batteries

Solar panels:
2 Nature Power 100 watt Polycrystalline panels
Tolerance: 3%
Voltage at Pmax(Vmp) 18.0V
Current at Pmax(Imp) 5.65A
Open circuit voltage(Isc) 21.6V
Short circuit voltage(Isc) 5.74A
Max system voltage 600VDC
Protection class Class A


I'm looking for a decent yet budget minded (Under $100) Solar Charge Controller to run my system.


Thank you!
Brian

[StirCrazy]

babock wrote:

StirCrazy wrote:
good one, notice how they don't show perfect weather... two reasons, 1 much smaller difference between the two, and
2 when do you every have perfect weather when you camp 😉

the only thing I wish they would have shown is when trees cast shadows over the pannel so you have 1/2 the pannel shadowed out, that's the biggest difference.

Steve

Gotta love the BS that people think. He tested it with the weather he had at the time. Was May in Maine!

I actually like that test, so not sure what your going on about. I just wish he had good weather so he could test the difference when it was partial shaded to show where the MPPT really shines. I have always said the MPPT is a better unit if you are set up properly, hence why I am building my campers system with a MPPT instead of the PWM they put on my 5th wheel.

Steve

[babock]

StirCrazy wrote:
good one, notice how they don't show perfect weather... two reasons, 1 much smaller difference between the two, and
2 when do you every have perfect weather when you camp 😉

the only thing I wish they would have shown is when trees cast shadows over the pannel so you have 1/2 the pannel shadowed out, that's the biggest difference.

Steve

Gotta love the BS that people think. He tested it with the weather he had at the time. Was May in Maine!

[StirCrazy]

bpounds wrote:
Worked for me. This is the first link offered.
Tested PWM versus MPPT

Here is the short and sweet of it:

good one, notice how they don't show perfect weather... two reasons, 1 much smaller difference between the two, and
2 when do you every have perfect weather when you camp 😉

the only thing I wish they would have shown is when trees cast shadows over the pannel so you have 1/2 the pannel shadowed out, that's the biggest difference.

Steve

[bpounds]

Worked for me. This is the first link offered.
Tested PWM versus MPPT

Here is the short and sweet of it:

[pianotuna]

Babock,

Great!

A link that takes me to a test of tires. LOL you certainly do know how to help others learn.

I was hoping that with your VAST knowledge, you would know of some non laboratory real life testing.

[babock]

pianotuna wrote:
Let's see a link.

https://lmgtfy.com/?q=Compare+the+performance+of+PWM+vs+MPPT

[pianotuna]

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.

[babock]

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.

[babock]

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.

[bpounds]

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?

[pianotuna]

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.

[StirCrazy]

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

[babock]

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.

[babock]

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.