Challenges with Solar on boats

[foggysail]

Originally Posted by foggysail

Isc is the short circuit solar panel current which means the output V is 0.

Yes, Isc shows on the A V P curves and one can assume that a panel that has an Isc of 20 amperes but the output voltage is 0 under that condition. No controller can have an input current greater than the output current, PERIOD!

Originally Posted by rabbi

Isc is the uppwer maximum current, that is real life current will always be less than Isc.


BTW: Of course SC can have input currents higher than output currents.
MPPT controllers capable of Step-up conversion convert 14V /10A input into 28V / 5A to charge a 24v battery bank. But true boost / buck MPPT controllers are a rare thing.

Originally Posted by rabbi

So Isc is what in your opinion, an imaginary number?
Its what it says, the shortcut current.

Real life current depends on the impedance of the SC, which an MPPT controller actively controls within limits (thats why Victron specifies safe operating limits Voc and Isc).
The key is: real life current is always less than Isc, and real life voltage is always less than Voc.



You are completely mistaken. Please google "MPPT boost converter" and take the time to read.

If you want to buy a product: Genasun
From the specs: Minimum voltage fr charging a 12v bank: 5V

Pls note: The Victron MPPT is not a boost converter, and at least I have never said so. I mentioned that MPPT controllers with boost converters do exist, not that Victron's MPPT is an implementation of such a thing.

Victron's claimed 98% efficiency has nothing to do with this.. I just means 100W in, 98W out. It does no say anything about voltages or currents.

This thread is titled "Challenges with Solar on Boats", not solar and their controllers for grids ties nor controllers for exoteric applications such as high voltage batteries including lithium that have limited applications to the average boat owners. Do boost converters exist? Of course! Are any found in solar applications discussed in popular boating forums? Slight chance of 'maybe." No need to look for a unique exception, lets stick to those that are of general interest!

Controller input current will never exceed a converter's output current other than by a small amount needed for a converter's housekeeping.

Now above quotes. Appears you have varying ideas of what Isc means. Your last above quote is correct.....however you forget where you quoted my also correct definition? No... Isc is not "So Isc is what in your opinion, an imaginary number? "

And impedance ONLY applies to AC applications. It is the angular sum of the combination of resistance which can consume power, capacitive and inductive reactances which cannot consume power. OH and it DOES involve imaginary numbers.

[john61ct]

Originally Posted by foggysail

nor controllers for exoteric applications such as high voltage batteries including lithium

FYI, LiFePO4 banks charge at lower voltage than lead. Any controller with adjustable setpoints including Victron is perfectly fine for LFP.

[rabbi]

Originally Posted by foggysail

This thread is titled "Challenges with Solar on Boats", not solar and their controllers for grids ties nor controllers for exoteric applications such as high voltage batteries including lithium that have limited applications to the average boat owners. Do boost converters exist? Of course! Are any found in solar applications discussed in popular boating forums? Slight chance of 'maybe." No need to look for a unique exception, lets stick to those that are of general interest!
...

Who is talking about grid ties, high voltage or whatever? Thje link I gave you is a totally valid 12v lead acid battery charger, and its not a very expensive one.
Do you want more links to other chargers that in your view are more appropriate for boat use?

So why have I posted this link? In a previous reply you said

Input current greater than output current.....REALLY??? Gees, another whack a mole!

The converter's input voltage must be greater than the battery's by several volts. Converters such as Victron's operating efficiency exceeds 98%. Within reason, the input current cannot be greater than the output. DO THE MATH.

which in my poor understanding of the english language means that you deny that such a thing can exist. Which I proved wrong using the product link

Originally Posted by foggysail

Now above quotes. Appears you have varying ideas of what Isc means. Your last above quote is correct.....however you forget where you quoted my also correct definition? No... Isc is not "So Isc is what in your opinion, an imaginary number? "

Please re-read my statements. Isc is the shortcut current. The shortcut current is the theoretical maximum current, so real life current is always less or equal to Isc, depending on operating point of the panel. Thats all I said.

[foggysail]

Well Rabbi---- I would prefer not posting but post I must. Yeah... I eat crow on somebody (you in this case) finding a boost converter. For that you earned my ........ just cannot get the words out

Cheers--

Foggysail

[rabbi]

Originally Posted by foggysail

Well Rabbi---- I would prefer not posting but post I must. Yeah... I eat crow on somebody (you in this case) finding a boost converter. For that you earned my ........ just cannot get the words out

Cheers--

Foggysail

OK


and since you are in the right mood:

Originally Posted by foggysail

And impedance ONLY applies to AC applications. It is the angular sum of the combination of resistance which can consume power, capacitive and inductive reactances which cannot consume power. OH and it DOES involve imaginary numbers.

You probably want to have a look at the following wikipedia articles.

Wikipedia "Maximum power point tracking":

The impedance seen by the panel derives the operating point of the solar panel. Thus by varying the impedance seen by the panel, the operating point can be moved towards peak power point.

Wikipedia "Electrical impedance":

When a circuit is driven with direct current (DC), there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle.

Obviously the folks at wikipedia don't follow your idea that impedance does only apply to AC applications.


BTW: as far as I understand MPPT technology these are internally just switching power converters. And, as you may know, in rapid DC switching applications impedance needs to be considered, not just resistance.

[foggysail]

Originally Posted by rabbi

OK


and since you are in the right mood:

You probably want to have a look at the following wikipedia articles.

Wikipedia "Maximum power point tracking":


Wikipedia "Electrical impedance":


Obviously the folks at wikipedia don't follow your idea that impedance does only apply to AC applications.


BTW: as far as I understand MPPT technology these are internally just switching power converters. And, as you may know, in rapid DC switching applications impedance needs to be considered, not just resistance.

Impedance, design engineers definitely concern themselves with impedance in things such as switching transformers. Although important here....leakage inductance and distributed capacitance, it is not as critical as found in high voltage transformers used specifically to drive magnetrons. There impedance is very critical.

Engineers working with power lines are really interested in reactances that interestingly have greater influence on power line voltage drops than resistance.

Now as to Willypeter or whatever they call themselves, just because they associate it with DC circuits changes nothing. But with today's engineering Millennials who knows. I prefer to associate impedance with AC circuitry where it belongs.

And copied from my trusty Webster's New World Dictionary (yes, I know it is aged):

"the total opposition offered by an electrical circuit to the flow of alternating current of a single frequency; it is the combination of resistance and reactance and is measured in ohms."

Enjoy your solar

[rabbi]

Originally Posted by foggysail

Enjoy your solar

On that we can agree

[newhaul]

Originally Posted by newhaul

I already posted all that information likely several pages back by now. Later today on the boat I will verify with my fluke clamp on .


Edit : I am disapearing (going sailing ) for a few days I will post my panel results when I get back . Pictures to follow.

Ok here goes. Renogy 100 watt mono panels. First is panel specs, second is charhe controller at 7am, second is controller at 10 am, the last is controller ah for the day. (Smokey from the bc fires affected collection of ah's .
Due to the smokey conditions the best output I saw was 8.7 amps. At ten. The batteries were full .( I was running all lights and thermoelectric cooler for loading. Cooler draws 4.8 amps )

[newhaul]

Originally Posted by newhaul

Ok here goes. Renogy 100 watt mono panels. First is panel specs, second is charhe controller at 7am, second is controller at 10 am, the last is controller ah for the day. (Smokey from the bc fires affected collection of ah's

Ok the 7am was unreadable here goes another try.

[arsenelupiga]

Originally Posted by rabbi

In my book buying a 15A controller with oversized panels can be a wise choice, as it's making best use of the available budget and real estate.

I like your idea of oversized panels. thinking to replace 2 x 180 w with 2x 360 w - sunpower. Will be straight replacement and size will fit nicely.

Already have victron 100/15 x 2.

Do you have any issues with your oversized panels setup ?

On sunny day have no issue with current setup but new setup would provide double power on substandard days.

[newhaul]

Originally Posted by arsenelupiga

I like your idea of oversized panels. thinking to replace 2 x 180 w with 2x 360 w - sunpower. Will be straight replacement and size will fit nicely.

Already have victron 100/15 x 2.

Do you have any issues with your oversized panels setup ?

On sunny day have no issue with current setup but new setup would provide double power on substandard days.

The biggie I see with this setup you propose is the amount of over paneling your new panels will be able to produce well over 20 amps. 360watts / 15 volts ( a bit over voltage but makes easy to do math in head.) = aprox 24 amps out put possible. Likely 20 amps + on a regular basis .
So lots of wasted possible power. But you have the controllers so use them for now until budget allows for replacement. ( keep the 100/15 as oh crap spares at that point.) This is jmho

[arsenelupiga]

Originally Posted by newhaul

The biggie I see with this setup you propose is the amount of over paneling your new panels will be able to produce well over 20 amps. 360watts / 15 volts ( a bit over voltage but makes easy to do math in head.) = aprox 24 amps out put possible. Likely 20 amps + on a regular basis .
So lots of wasted possible power. But you have the controllers so use them for now until budget allows for replacement. ( keep the 100/15 as oh crap spares at that point.) This is jmho

not much point increasing controllers as have max 480AH battery bank. And cant increase it easily due to space constraints and also boat balance issues, and LI is not encouraged by Lagoon, so will not go there.

[newhaul]

Originally Posted by arsenelupiga

not much point increasing controllers as have max 480AH battery bank. And cant increase it easily due to space constraints and also boat balance issues, and LI is not encouraged by Lagoon, so will not go there.

There's always refrigeration system and watermaker to run off excess potential power in the afternoons. Could also dump excess potential into a low volt water heater element 400 watts will help with shower water for happy wife happy life scenario. ( did I mention fresh water from watermaker)

[foggysail]

I installed a Victron 150/70 controller before I upgaded my panels. Later I realized I should have stuck with my original plan to purchase the 150/85. I thought I would never ever see a charge current over 70 amperes. I was incorrect.

My new panels are 4 each 295 watt 32Vmp mono panels for a total of 1180 potential watts. Now I am controller limited to about 980 watt using a battery voltage of 14 for calculation.

I have seen 69 amperes! OK, so I suffer from over paneling, should have purchased the panels prior to the controller. The world has not come to an end however. I may not get peak performance but I do get better performance during cloudy days. For batteries I have 860AH bank of golf carts. There are other considerations helping to limit their output such a sun/panel angle, cleanliness for example.

After the season ends, I plan selling this controller, maybe in the $300-325 range and correct my mistake with a 150/85 next season.

[john61ct]

Originally Posted by arsenelupiga

not much point increasing controllers as have max 480AH battery bank. And cant increase it easily due to space constraints and also boat balance issues, and LI is not encouraged by Lagoon, so will not go there.

I also agree, depending on your average conditions, you may be sacrificing "too much" (subjective) peak power production putting in 360w (theoretical) per 75/15, which will only output 220-240w max in reality.

To test I would recommend swapping in a single 100/30 to start, and see how much more actual AH per day you get. If you do that, please post results here.