Parallel two solar controllers??

[s/v Jedi]

Originally Posted by hpeer

^+1

Polite behavior is appreciated.

While Jedi and I disagreed about what you can expect from a panel his charging maths and mine were within 5%.

The OP has already purchased the panels and the controllers. I believe the point is to help him use what he has to best usage.

The Victron 75/15 will only do so much.

I have lost the will to beat around the bush for politeness after the cr@p people gave me on this forum over the years. Thing is that I give solid info, free from any political correctness so that readers can take it and use it to their advantage. I remember, when I sold this kind of info during my career I added that thing called politeness and would need find ways to say the customer was wrong without actually saying it. Here my info is free of charge and barebones haha

I don’t think I disagree much with what you wrote; if you see max. 250W from a 320W panel then you have a really bad panel or you live too far from the sun or one of many other reasons. Thing is, that the panel ratings are actual, as verified by test under regulated conditions. When you can’t get that performance from a panel then the conditions in which you test are worse than the conditions used for the rating tests or something is wrong with panel or controller.
Like I wrote, new panels perform better than rating in order to achieve warranted performance during it’s lifespan (during which performance slowly degrades)

[kmacdonald]

If you read the data sheet for the victron solar charge controllers it clearly say exceeding pv short circuit current rating of the controller may damage it. For the 75/15, is is 15 amps. Jedi is wrong on that point but accurate elsewhere.

[kmacdonald]

For what it's worth, my 160 watt panels have output 170+ watts on ocasion.

[s/v Jedi]

Originally Posted by kmacdonald

If you read the data sheet for the victron solar charge controllers it clearly say exceeding pv short circuit current rating of the controller may damage it. For the 75/15, is is 15 amps. Jedi is wrong on that point but accurate elsewhere.

Interesting this max. Isc in the specs, I see you are correct. That said, max. Isc of 15A for the 75/15 is coincidentally the same number, because “15” in “75/15” does not mean a max Isc of 15A but a max. load of 15A. The load is the battery, i.e. the max. charge current is 15A. It’s the same number.

For other controllers, the number is not the same, i.e. my 150/45 can handle Isc of 50A, as do the 150/60 and the 150/70. But my controller can only charge the battery with 45A, which is the meaning of “45” in “150/45”.

Also, like I wrote earlier, this number is not fixed because the controller de-rates automatically for temperature. I thought that was all until last winter I saw them perform over rated output, so when it’s cold, they can do a little better until they warm up of course

So these panels of the OP have an Isc of 10A so even with both panels in series it would not damage the controller because it’s well below 15A, but I did not take this into consideration. I guess as long as your array Voc is well above battery voltage and controller is reasonably matched, things can’t go wrong.

[skipmac]

Originally Posted by hpeer

This is a what is SOLD, it is not what HAPPENS.

Your panels will NOT put out 320WATTS. You need to look at the maximum Power Point voltage and current. Unfortunately you spec sheet does not list that.

In reality you will have something like 8-1/2A at 30Volts or very roughly 250Watts MAXIMUM discounting wire loss, dirt and everything else.

Then the MPPT controller takes that 8-1/2A and 30Volts and outputs about 14Volts at some specified Amperage. Lets say 15A for a Victron 75/15.

So 15A at 14V is 210 WATTS. THAT is about the MAXIMUM power you will get.

But even if you could put 2 each 75/15’s in parallel you will get something less than 250Watts because the devices are not 100% efficient.

That is why describing a solar panel as 320W may be correct but is completly misleading. Your actual MAXIMUM available power is about 2/3 of that “advertised” power.

Again, if something I have written is substantially wrong please point it out.

PS:

One could ask; Why not just get a bigger MPPT controller, say 25A? Fair question. Above I was using MAXIMUM capability. In real world installations you plenty of additional factors which limit the available power. The maximum numbers are calculated at a standard temperature with full brilliant sunshine directly overhead. Very rare to get those conditions. The the installation has resistance in the wire and the connectors and connections. Then there is dust, panel angle, shadow, clouds, bird poop….. all of which degrade your output. You will be lucky to ever see 200W. All in the 75/15 is a good pragmatic match to a 320 watt panel. One on one.

I completely understand the issues with efficiencies, conversion losses, Voc vs voltage under load, angle of the sun, dirty panels, lower output due to heat, etc, etc, etc. Please note that I have been using simplified conversions which I believe I mentioned, for the sake of brevity and clarity in the discussion. Perhaps I should mention that long ago in a galaxy far away I earned a degree in EE with a focus on IC fabrication which included a course on photocell design so I'm not entirely ignorant in this area.

So of course I do not expect a panel rated at 320 W to give me an output of 26 amps, even under ideal conditions. At the same time I will guarantee that I will get more than the 8.5 or 10 amps that you claim when running through a solar controller MPPT or PWM, that converts the panel output to 13.5-14V for charging. FYI I regularly see 10 amps each from the older 240 W panels using the same Victron 75/15 controller.

[thomm225]

Originally Posted by s/v Jedi

You’re wrong, Google it. Voc is open circuit voltage, never called floating voltage by anyone..

Actually I'm not wrong.

I never said VOC was called floating voltage.

Not sure how you got that out of what I wrote. I even mentioned it could confuse some by using the term.

My point was that if you knew what a floating voltage was it's easier to understand VOC (Voltage Open Circuit)

I was simply trying to make the term easier to understand. You aren't going to see the VOC voltage and max current (short circuit current) with the panel online.

I've never tested the short circuit current out of a panel by have made test checks on my panels VOC with a meter on new panels in the Sun just to verify they are working

[Wotname]

Originally Posted by thomm225

Actually I'm not wrong.

I never said VOC was called floating voltage.

Not sure how you got that out of what I wrote. I even mentioned it could confuse some by using the term.

My point was that if you knew what a floating voltage was it's easier to understand VOC (Voltage open circuit)

I was simply trying to make the term easier to understand. You aren't going to see the VOC voltage and max current (short circuit current) with the panel online.

I've never tested the short circuit current out of a panel by have made test checks on my panels VOC with a meter on new panels in the Sun just to verify they are working

Sure seemed like you did in your previous post; perhaps you meant to write something else.

Originally Posted by thomm225

I believe the chart shows 10 amps at short circuit. (max current flow) Maybe that helps.

VOC (Voltage Open Circuit) is no load/open circuit so no current flow which is why the voltage is so high

In electronics, we used to call this float voltage but that would really cause confusion with controller float setting if they called it that

[thomm225]

Originally Posted by Wotname

Ahh...No. I am not disputing that you learnt this definition of 'floating voltage' but I can say you were incorrectly taught. Your definition maybe helpful to you in some circumstances but it can not be used as a definition of floating voltage.

As I said, it can be confusing using the term floating voltage.

First time I heard it was in 1977 or so. (and there wasn't a whole lot of talk on solar back then)

It has nothing to do with VOC (Voltage Open Circuit) but is similar in that there is no current flow.

It was a way to recognize a problem with a circuit while troubleshooting as I mentioned earlier but I guess that was too much for your average person to understand especially since we these days very rarely even troubleshoot circuits. We just remove and replace the whole circuit card.

I thought it would help folks better understand what is meant by an open circuit voltage but it just confused those that don't have the background.

It's simply something that automatically clicks for me as when I see my panels VOC at around 22 volts then when I hook it to the battery and it has current flow and a load it drops to the battery voltage whether that is 11.5 or 14.1 volts.

With my old PWM controller, the panel side of the controller would actually approach VOC after my batteries were totally charged and the current flow had decreased most of the way.

[s/v Jedi]

Originally Posted by Wotname

Sure seemed like you did in your previous post; perhaps you meant to write something else.

Yeah, he clearly knows what it is but just got the wrong term “floating voltage” in there and puts heels in the sand now… doesn’t work with EE’s abound

[thomm225]

Originally Posted by Wotname

Sure seemed like you did in your previous post; perhaps you meant to write something else.

Yeah that does look confusing.

Point I was trying to make was to illuminate what open circuit voltage was for those that weren't use to the concept.

But I guess the term is just too old school to use these days.

I mean there is very little circuit troubleshooting going on now. Most times it's just troubleshoot to the failed board/circuit card and replace. (toss the bad one in the trash)

We used the term floating voltage when there was no current flow in a circuit ......caused by an open. Broken solder run, open transistor, diode, resister, etc. And when you saw that you knew you were getting close to the failed component and sometimes could just test those with a meter (or octopus) on the board and find the problem.

https://www.antiqueradios.com/forums...p?f=8&t=240087

I guess you are old school if you were one of us that used to troubleshoot computer CPU boards with a schematic and O'scope or systems analyzer to trap high speed trigger signals

Now days we replace the whole motherboard or entire computer but if it's software or a cyber intrusion that's different.......

[Wotname]

Originally Posted by thomm225

Yeah that does look confusing.

Point I was trying to make was to illuminate what open circuit voltage was for those that weren't use to the concept.

But I guess the term is just too old school to use these days.

I mean there is very little circuit troubleshooting going on now. Most times it's just troubleshoot to the failed board/circuit card and replace. (toss the bad one in the trash)

We used the term floating voltage when there was no current flow in a circuit ......caused by an open. Broken solder run, open transistor, diode, resister, etc. And when you saw that you knew you were getting close to the failed component and sometimes could just test those with a meter (or octopus) on the board and find the problem.

https://www.antiqueradios.com/forums...p?f=8&t=240087

I guess you are old school if you were one of us that used to troubleshoot computer CPU boards with a schematic and O'scope or systems analyzer to trap high speed trigger signals

Now days we replace the whole motherboard or entire computer but if it's software or a cyber intrusion that's different.......

Well, Floating Voltage is still a term in use today and when used correctly, it is a helpful concept.

As for the octopus (e.g. Huntron Tracker etc), I do remember it was used by those who couldn't understand or do circuit analysis at a component level but not so much by professionals.

As for old school, I cut my teeth when telecommunication switching networks were all relays, diodes and strapping blocks, you may call me Mr Old Phart

[noelex 77]

Originally Posted by hpeer

That is why describing a solar panel as 320W may be correct but is completly misleading. Your actual MAXIMUM available power is about 2/3 of that “advertised” power.

Again, if something I have written is substantially wrong please point it out.

If the solar panel and controller are performing correctly and the installation is well done, you should occasionally be seeing the rated output of the panel (or at least very close to this value) in areas of good solar insolation.

With good panels and exceptional conditions you can even see values above the panel’s rating for brief periods.

The photo below is from is the output from one of my 335w panels.

Regarding the other questions raised in this thread, just see Jedi’s post .

You certainly cannot use a PWM controller with high voltage panels, except perhaps in an emergency. You can use multiple MPPT controllers, but you cannot connect multiple controllers to one panel.

[Jim Cate]

I'll add my thanks to Jedi and to Nolex for substantive and correct posts in this thread. We've seen an unusual amount of baseless BS upthread, quibbling about trivial bits imbedded in a sea of misinformation. One would think it was politics rather than simple engineering.

And Nolex, we too have seen numbers that exceed the rated output of our 2x200 watt 40 volt panels, going through a Victron 30/75. Peak ever was 440, but quite a number of >400 watt periods... and this is at 43 degrees south, with poorish sun angles. I'm quite sure that in locations where near 90 degree elevation of the sun happens the numbers would be higher (until the panels heated up!).

Here's to better understanding of our simple systems on board our boats!

Jim

[thomm225]

Originally Posted by Wotname

Well, Floating Voltage is still a term in use today and when used correctly, it is a helpful concept.

As for the octopus (e.g. Huntron Tracker etc), I do remember it was used by those who couldn't understand or do circuit analysis at a component level but not so much by professionals.

As for old school, I cut my teeth when telecommunication switching networks were all relays, diodes and strapping blocks, you may call me Mr Old Phart

Well I used the term floating voltage correctly earlier, but it just threw folks for a loop who didn't have the background I have in electronics/computers etc. I could have worded the statement a little better though

Voltage Open Circuit (VOC) in solar or floating voltage in electronics is basically the same though since there is no circuit flow. I simply thought to add that thinking it may help others understand better

As far as the Octopus and Huntron Trackers, we used those to troubleshoot and repair circuit boards when there were no schematics available or when the systems were being used and we couldn't install the board on an extender and troubleshoot it with an o'scope and schematics but had to troubleshoot on the bench instead.

We also called a voltage floating with TTL circuits. If say one output of an IC was 2 volts we said it was floating.

It should have been a high (5 volts) or a low ground or 0. TTL was used for the early binary 1's and 0's circuits so they could count later used by computers.

Another definition of float in electronics was when a circuit, system or unit wasn't grounded. It was said to be floating.

Like all the systems on my boat, there's no ground to the engine then to the sea thru the prop as before.

In the photos, I was low on battery power so hooked up my two 20 watt panels directly to the batteries and was monitoring the voltage with the meter and on one of the PWM controllers with a display

All panels were getting max Sun light for the most part. None of my panels are permanently mounted so I can aim them directly at the Sun if I need to.

The full 155 watts of panels that I had are hooked up. Two 20 watt panels direct, my 10 year old 65 watt panel, and a Renogy 50 watt panel thru controllers

The 20's and the 65 are attached using some old 14 gauge wire we had left over from another project.

[hpeer]

Originally Posted by s/v Jedi

I have lost the will to beat around the bush for politeness after the cr@p people gave me on this forum over the years. Thing is that I give solid info, free from any political correctness so that readers can take it and use it to their advantage. I remember, when I sold this kind of info during my career I added that thing called politeness and would need find ways to say the customer was wrong without actually saying it. Here my info is free of charge and barebones haha

I don’t think I disagree much with what you wrote; if you see max. 250W from a 320W panel then you have a really bad panel or you live too far from the sun or one of many other reasons. Thing is, that the panel ratings are actual, as verified by test under regulated conditions. When you can’t get that performance from a panel then the conditions in which you test are worse than the conditions used for the rating tests or something is wrong with panel or controller.
Like I wrote, new panels perform better than rating in order to achieve warranted performance during it’s lifespan (during which performance slowly degrades)

Jedi;

I have no difficulty with the above post. I do disagree with some of your statements, but there could be many reasons for that. In the end we come to the same technical situation/solution, so how different can it be?

I am sorry you got a lot of guff for your previous posts. And yes many folks post silly things and yes it is annoying.

I appreciate your above reply and openness and free advice and frankly, deescalation. I hope to reciprocate that friendly response. It is an uncommon act these days.

Thank you.