Multiple MPPT Solar Charge Controllers to the same battery bank

[Zwy]

Wow, he finally gets it.

It's a dumb argument. Of course adding panels will produce more. One can configure strings to take advantage of extra panels, add more SCC's and harvest any potential yield instead of part of it.

You're trying to make it sound like you won some argument, well, you haven't. I stand by my statements.

What you are missing is that that may not be the optimal solution in every case.

You obviously did not read thru any of the links. 3 weeks with 20 minutes of sun is one example. How would overpaneling help that situation? If the sun shined at peak power for 20 minutes in a week, heck I'll even give you 1 hour, would the SCC capture more yield with overpaneling than it would if the SCC was underpaneled?

Answer that question. I shall return after lunch to discover your answer.

 

[Bop]

And NOPE- he still missed the point completely...

You STILL missed that your battery bank has a LIMITED amount of current it can accept- if you have the array set to a safe limit in the good conditions, then it will make LESS in POOR conditions...
If you experience POOR weather conditions a lot of the time, then you are losing charging capability- when you need it the MOST...

By overpanelling- you are trading generation capability in the best conditions, (a few hours a day in good weather, none in bad weather) for MORE charging ability in the poorer conditions (ie early morning/late afternoon in good weather, all day in poorer weather)

It WORKS...

 

[Zwy]

But still doesn't get that in order to push production up in poor conditions, you have to limit it in good conditions...
Sighs (and I don't expect he ever will...) old dog, new tricks etc...

Why limit yield?

You must be an old dog, said you had 4 decades of the same experience and haven't learned the new tricks.

 

[Texas-Mark]

Go back and read what I have written in this thread thus far, you might be able to understand it after a few times.

We can say the same.

You are the one who initially claimed overpanneleing will never exceed an underpanneled system. If you still believe that, so be it.

You remind me of the guy who claimed we have all been charging our batteries wrong. LOL

 

[Andrewr05]

If the sun shined at peak power for 20 minutes in a week, heck I'll even give you 1 hour...

would the SCC capture more yield with overpaneling than it would if the SCC was underpaneled?

Of course it would.

I don't even know how you come to the logic that it couldn't.

If I stick two pieces of paper towel on some water that I spilled, won't the two pieces of paper towel absorb more water?

I think you're somehow conflating what we are saying to mean that we are trying to imply that you can extract more power than exists.

If you have a 400 watt solar panel and there's so little sun out on a given day that it's only producing 80 Watts of power and then next to it you also have a 400 watt solar panel, that other solar panel would also be in taking in 80 watts of power.

So, literally during inclement weather the more solar panels you have, the more power you were able to extract.
That's like the basic 101 of householder panels work on any day, not just a shitty weather day.

Peak sun hours to me are largely irrelevant, because I know that total all day long at least some form of wattage is going to be coming in.

 

[Zwy]

And NOPE- he still missed the point completely...

I haven't missed anything.

You STILL missed that your battery bank has a LIMITED amount of current it can accept- if you have the array set to a safe limit in the good conditions, then it will make LESS in POOR conditions...
If you experience POOR weather conditions a lot of the time, then you are losing charging capability- when you need it the MOST...

Yep, old dog that "learned" with lead acid.

Put in a bigger bank and maximize yield from PV and get back to me. It is possible you might learn some new tricks.

By overpanelling- you are trading generation capability in the best conditions, (a few hours a day in good weather, none in bad weather) for MORE charging ability in the poorer conditions (ie early morning/late afternoon in good weather, all day in poorer weather)

It WORKS...

No need, I have a large enough battery bank plus dump loads to handle days of high production and capture all potential yield on days of poor production.

It WORKS......

 

[Andrewr05]

It WORKS......

Unless I've missed one of the posts, I don't believe anybody so far in any way has said anything to the contrary.

We are just also saying that something else is also possible.

 

[Zwy]

Of course it would.

I don't even know how you come to the logic that it couldn't.

If I stick two pieces of paper towel on some water that I spilled, won't the two pieces of paper towel absorb more water?

I never stated that more panels would not produce more power. We all know they will. What some have tried to claim is that X number of panels will produce more power by just overpaneling the SCC instead of underpaneling. In actuality, the yield will be less long term due to clipping.

I think you're somehow conflating what we are saying to mean that we are trying to imply that you can extract more power than exists.

There you go. You get that part.

Some are trying to confuse the argument by claiming I said more panels won't produce more power. Never said it. It's a strawman argument on their part.

 

[Andrewr05]

I never stated that more panels would not produce more power. We all know they will. What some have tried to claim is that X number of panels will produce more power by just overpaneling the SCC instead of underpaneling. In actuality, the yield will be less long term due to clipping.

Again how many bad weather days we are talking about.

Nobody here has argued that it isn't a wasteful method.
From the get-go, I think those of us that are talking about this have fully understood and made it aware that we understand that on a normal day the extra current is being wasted.

I think we can all agree that that's the reality of over-paneling.

 

[Zwy]

Again how many bad weather days we are talking about.

It isn't just about bad weather days. We can take today as an example. Sun shined for about 15 minutes this morning at about 9 am, then went behind heavy cloud cover. My battery bank was down to under 40% as the heat pump ran all night and yesterday the sun went behind the clouds at about 2 pm. Very little production with the heavy cloud cover. There was very little PV to power loads.

The sky cleared at a little after 11 am today. It is now clear but it almost looks like late afternoon it might cloud back over.

Would overpaneling my SCC's lead to increased yield for the day or would underpaneling? We are talking peak sun hours here so overpaneling will lead to clipping as the sun is bright now and I'm pulling close to 100% from my array. My bank has plenty of capacity to allow for capturing any potential yield from PV. By underpaneling, I can capture all those photons and put them to use by underpaneling.

Many days here this time of year are clear skies until late in the day, then cloud cover. Or cloud cover in the morning with clear skies later in the day. By harvesting all potential yield mid day at peak sun, I can put that energy into my batteries for later use, such as heating my house overnight.

Nobody here has argued that it isn't a wasteful method.
From the get-go, I think those of us that are talking about this have fully understood and made it aware that we understand that on a normal day the extra current is being wasted.

I think we can all agree that that's the reality of over-paneling.

I look at it this way, I'd spend the money on a SCC before overpaneling. The EG4 MPPT is $399. I can capture all yield and use it, the excess yield can pay back the $399 fairly quickly. Today I will charge my bank up enough in a short time frame that I can heat my house overnight for free.

 

[Texas-Mark]

We all know they will. What some have tried to claim is that X number of panels will produce more power by just overpaneling the SCC instead of underpaneling. In actuality, the yield will be less long term due to clipping.

Not necessarily. It may clip for lets say an hour. What about the rest of the day when it's producing more than what was lost? What about cloudy days? THAT is what you fail acknowledge and you think your "one size fits all" approach is the only one that is correct.

Some are trying to confuse the argument by claiming I said more panels won't produce more power. Never said it.

Actually you did when you said overpanneling (adding more panels) won't produce more than underpaneling. Unless you were somehow only talking about peak sun when clipping may occur. But nobody here would think that.

 

[Andrewr05]

But nobody here would think that.

Agreed
And I don't get what people are stuck on peak hours.
I'm not saying it's not important, but you make power the other 95% of the day as well.

 

[Texas-Mark]

And I don't get what people are stuck on peak hours.

Unless it was seriously overpanneled, that would be the only time it would be clipping and power was lost. If one is clipping all day, then yes, a second CC would probably be a better option.

 

[Andrewr05]

Would overpaneling my SCC's lead to increased yield for the day or would underpaneling?

I think every time you say underpaneling I think you just mean normal panelling. I don't understand why you're wording it that way.

But also the answer to your question is, YES.
You would still be capturing the same amount of power during those peak hours (your charge controller can only take in a set amount of Amps), but during the other hours of the day (or during cloudy weather) you would be getting more power coming in.

 

[Texas-Mark]

I think every time you say underpaneling I think you just mean normal panelling. I don't understand why you're wording it that way

I agree. The term "underpaneling" can mean 50% of CC capability in which case even getting it to "normal" with more panels will yield an increase.

 

[sunshine_eggo]

I'm under-paneled.

I'm just too lazy to put the other 3kW on the 250/100 because the first 3kW/50A is doing me fine.

 

[Zwy]

Not necessarily. It may clip for lets say an hour.

It will clip for close to 2.5 hours, maybe longer if sun appeared at 11 am and still have good sun at 2 pm.

What about the rest of the day when it's producing more than what was lost?

You don't peak output the rest of the day as the sun has moved past peak.

What about cloudy days?

You get the same yield from X number of panels overpaneling a SCC or not. This morning was a prime example, each panel was producing the maximum it could from the available sunlight.

My array doesn't get bigger or smaller, it stays the same size day after day. Unless somebody has been sneaking around and taking panels away when I'm not looking.

THAT is what you fail acknowledge and you think your "one size fits all" approach is the only one that is correct.

I'm giving a completely different approach here. Large battery bank to capture as much production as possible and using enough SCC's to capture any yield. If you are close to max rating for charging the bank, then you need more storage. If grid tied, it wouldn't make any sense to overpanel an inverter as the grid is an endless battery. Put the maximum amount of power you can onto the grid at any given time so it can be pulled off the grid later.

Actually you did when you said overpanneling (adding more panels) won't produce more than underpaneling.

Overpaneling will only produce more by adding more panels. That is the strawman argument. I could add the same number of panels with another SCC and outproduce the overpaneled SCC any day.

You fail to grasp that concept. Adding more panels in both cases will increase production over X number of panels. The strawman argument is always, well I have more panels because I overpaneled. It is ludicrous.

If add more panels with underpaneling the
SCC's and enough SCC to cover it, it will produce more.

All you need is a load to capture the excess into something useable. Lead acid suffered from needing an absorption charge to prevent sulfation and internal resistance would increase as SOC increased. This required long periods of production thru the day. LFP doesn't suffer from the need to extend charging hours over long periods of time, take every watt you can get at each second and shove it into the LFP. It will take it.

One member tried claiming it would be excessive charge rate. If done correctly the way it should be done with LFP, you want at least a 5:1 ratio of battery capacity to PV max output. How is that anywhere close to hitting C rate of the battery bank? One could even go with a lower ratio of battery to PV, as long as a manufacturer C rate is not exceeded. In his example, he showed a 400Ah battery cell with a C rate of C3 which would be 1200A. In order to exceed the C rate would take PV of over 60Kw. I'd like to see that array.

Unless you were somehow only talking about peak sun when clipping may occur. But nobody here would think that.

4 hours of peak sun and let's say 4 400W panels on their own SCC. Do the math on how many more Kwh it produces compared to an array that is overpaneled and clipping the 400W per string during those 4 hours.

It isn't only that aspect, I still get the yield the rest of the day. I have yet to see an array that changes the number of panels depending on weather conditions or the time of day. You install X number of panels that fit the mounts. Those panels have a yield potential = to the amount of sunlight hitting the panels each day.

 

[Zwy]

I agree. The term "underpaneling" can mean 50% of CC capability in which case even getting it to "normal" with more panels will yield an increase.

Nope, I underpanel based upon what the string VOC will be.

I run all strings in series with no parallel strings.

If the SCC can take 5kw, it really doesn't matter, the strings that feed it are based upon how many panels I can series string without exceeding VOC. Things have changed with high VOC rated charge controllers and higher output panels. Many are stuck with the idea of paralleling strings and running max amps to get to the SCC peak output. Not me, I'm stringing panels in series to get voltage up as high as the SCC will let me and just add panels to get under that VOC rating with my coldest temps. The old days of 250W panels are behind us and so is lower VOC rated SCC's.

Whether you understand how that works, I can't say. Think out of the box.

 

[Zwy]

Agreed
And I don't get what people are stuck on peak hours.

Pull the max power when you can get it, whether it is early morning or peak sun. In my example for today, the front came thru and pushed those heavy clouds out. That is lost production time. Time is constant, there are only so many hours available for production each day. The days can get longer or shorter thru the year but there is still only so much time to capture the yield.

I'm not saying it's not important, but you make power the other 95% of the day as well.

I will pull as much power out of the panels as the panels can produce and put it in storage or power loads. Right now I'm at 71% SOC and still charging my 58Kwh bank at 5% and it is 4 pm. I can use the extra 10% I gained by pulling full production during peak to heat my house for free, plus my wife did laundry and ran the dishwasher. And remember, the bank was at 36% this morning at 9:58 am. I just checked on SA. Array size is 8.4Kw.

 

[Zwy]

I'm under-paneled.

I'm just too lazy to put the other 3kW on the 250/100 because the first 3kW/50A is doing me fine.

See, underpaneling works, you're getting full production from the panels you have producing, enough to meet the need.

 

[Texas-Mark]

It will clip for close to 2.5 hours, maybe longer if sun appeared at 11 am and still have good sun at 2 pm.

It will clip depending on just how much it is overpaneled (along with angle of panels and temperature). And of course whether or not it is cloudy (which is the whole point of overpaneling). 2.5 hours is just a WAG on your part. And how would you even know any real life figures if you refuse to overpanel???

 

[Zwy]

It will clip depending on just how much it is overpaneled (along with angle of panels and temperature). And of course whether or not it is cloudy (which is the whole point of overpaneling). 2.5 hours is just a WAG on your part. And how would you even know any real life figures if you refuse to overpanel???

I can say I tried.

You just keep doing what you're doing, it works for you. Others reading this might grasp the concept and build their system accordingly.

X number of panels can only produce X number of watts for the given sunlight hitting them.

 

[Texas-Mark]

X number of panels can only produce X number of watts for the given sunlight hitting them.

Good grief, you are back on this red herring again?

You just keep doing what you're doing, it works for you. Others reading this might grasp the concept and build their system accordingly.

I'm quite sure it works for many since that is what they are doing.

Nobody ever said they could not add another controller. That was never the point of this "debate". You asked "Please explain how overpaneling for cloudy days increases yield compared to underpaneling", and several have tried to explain it to you. Sorry you still can't grasp the concept.

 

[Zwy]

Good grief, you are back on this red herring again?

Explain to me how X number of panels produces more power by overpaneling?

That was my question back to you. You never answered it. You added panels. But that wasn't the question, it was X number of panels.

I'm quite sure it works for many since that is what they are doing.

Some habits are very hard to break.

Nobody ever said they could not add another controller. That was never the point of this "debate".

If you add panels, I get to add SCC's.

You asked "Please explain how overpaneling for cloudy days increases yield compared to underpaneling", and several have tried to explain it to you. Sorry you still can't grasp the concept.

I'll be more specific as you haven't answered that question. Array is 10Kw. Cloudy day and yield is 3Kw potential.

How does overpaneling the SCC increase the yield of that 10Kw array compared to having enough SCC to pull full output?

 

[Texas-Mark]

Explain to me how X number of panels produces more power by overpaneling?

Perhaps if you go back and actually read the past few pages of posts you would see that it it has been explained several times. Once again, overpaneling = more panels = more power available.

I'll be more specific as you haven't answered that question. Array is 10Kw. Cloudy day and yield is 3Kw potential.

How does overpaneling the SCC increase the yield of that 10Kw array compared to having enough SCC to pull full output?

Are you serious??? Now I think we are all just being pranked.