Multiple MPPT Solar Charge Controllers to the same battery bank

[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.

 

[Zwy]

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.

You are adding more panels, of course you can produce more with more panels. If adding more panels, I add SCC's.

It would be kinda stupid to hang panels and not hook them to a charge controller. What would be the purpose?

Maybe it is magic fairy dust that overpaneling causes more output from X number of panels? Sorry, don't have any extra magic fairy dust.

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

Quite serious. No pranks.

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?
Attempting another deflection? Strawman did not work?

 

[Andrewr05]

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

Over panelling it does not change the yield of your existing 10kW array.

The maximum it could ever make is 10kW.
I don't know what you mean by "pull full output".

 

[Texas-Mark]

Over panelling it does not change the yield of your existing 10kW array.

The maximum it could ever make is 10kW.

This is true, but it will allow for more power availability when cloudy. Thus he would get more than 3Kw when cloudy.

I don't know what you mean by "pull full output".

I don't know either. It sounds like he thinks it will still pull full power (10Kw) even in cloudy conditions. Nothing in that last post makes sense.

 

[Zwy]

Over panelling it does not change the yield of your existing 10kW array.

That is correct, the max yield will be 10Kw.

There are some factors that affect peak output such as albedo but we won't use that for part of this discussion.

The maximum it could ever make is 10kW.

Yes, the max it can output is 10Kw.

I don't know what you mean by "pull full output".

Pull full output= having enough SCC capacity to pull 10Kw from the array when it hits peak production

10Kw array = 10Kw of SCC

Maybe there is some misunderstanding on underpaneling. My definition is for example my array, a 5.5Kw SCC with 4.24Kw of panels it pulls from.

Even though the SCC has more capacity, I'm not using it. If I was to overpanel it, it would be more than 5.5Kw (and it can only output 100A max so keep that in mind, that also has an effect) provided it stays under the VOC rating.

If we take that same 10Kw array and use SCC's that are only capable of 4.5Kw the max that can be pulled is 9Kw. The SCC's are overpaneled. Some will claim they can pull that 9Kw over a longer period but reality is this, if the SCC can pull full output of 10Kw at peak sun, it can pull any yield the panels can produce when it isn't peak sun. It will not be a longer period, it will be the same length of time, the only change will be the 10Kw can be pulled from that 10Kw array when it reaches full yield potential if the SCC's are underpaneled.

I can say I have ran SCC's overpaneled. The first AIO inverters on my array were EG4 6500EX's. These would cap my yield at 3.9Kw from 4.2Kw of panels per MPPT. After replacing the 6500EX's with LV6548's and installing the EG4 MPPT's for high string VOC, I now commonly see full panel output over 4.2Kw with a peak of 4.6Kw with some albedo. The panels are the same, no changes in wiring, just the change of the MPPT's. Would the 6500EX's outproduced the EG4 MPPT's on a cloudy day? No, they would not, the yield would be the same on a cloudy day.

 

[Zwy]

This is true, but it will allow for more power availability when cloudy. Thus he would get more than 3Kw when cloudy.

Enlighten me on this power availability.

If the 10Kw array is outputting 3Kw when cloudy, how does overpaneling a SCC make this "power availability" more than 3Kw?

I don't know either. It sounds like he thinks it will still pull full power (10Kw) even in cloudy conditions. Nothing in that last post makes sense.

You're a funny guy!