Multiple MPPT Solar Charge Controllers to the same battery bank

[Zwy]

Please explain how this is better than overpanneling for cloudy days.

Please explain how overpaneling for cloudy days increases yield compared to underpaneling.

For the same number of panels, the yield will be the same. The panels can produce X number of watts, the SCC will pull X number of watts. You will not get more yield by overpaneling on a cloudy day than one would if underpaneled. Where does the mysterious extra PV energy come from due to overpaneling? Underpaneling a SCC may result in adding another SCC, but the yield from the panel is still the same. I have no idea where this myth came from that states overpaneling produces more PV on a cloudy day. A panel has X potential and X potential is all a SCC can pull from it regardless of overpaneling or not.

I have expressed my opinion several times regarding overpaneling. Here is one post. https://diysolarforum.com/threads/w...rom-china-and-import-to-usa.70717/post-937709 and another https://diysolarforum.com/threads/eg4-6000xp-released-ordered-lets-go.71306/page-4#post-906494 and another https://diysolarforum.com/threads/over-panel-risk.35756/post-449651 I do suggest underpaneling any SCC, this way one can harvest any potential yield at any given time. If this results in excess production, then find a dump load to use the excess.

The second reason is a member here with a Youtube channel stated the EG4 MPPT he was using failed shortly after making a video about the EG4 MPPT. When pressed about what the setup was for PV, he never answered. Either it was over on VOC on a cold day or it was overpaneled. We will never know as he never answered any questions.

I setup my system to maximize yield at any given point. I don't see any purpose to overpaneling. Some may argue it provides a more even ouput of power thru a day, why not harvest any potential yield and put it either in battery storage or a dump load?

 

[Texas-Mark]

For the same number of panels, the yield will be the same. The panels can produce X number of watts, the SCC will pull X number of watts. You will not get more yield by overpaneling on a cloudy day than one would if underpaneled. Where does the mysterious extra PV energy come from due to overpaneling?

Maybe you are using different terminology than me. But overpanneling to me, means adding.........more panels.

 

[Andrewr05]

You over-panel in parallel, not in series.

So there's no danger of going over the max PV voltage ratings, you just set it up to intentionally over produce current on a typical sunny/summer day and then on a cloudy/winter day you when you have significant losses you still (hopefully) meet your ratings.

 

[Zwy]

Maybe you are using different terminology than me.

But overpanneling to me, means adding.........more panels.

Where does the mysterious extra PV energy come from due to overpaneling?

For a given number of panels, there will not be any extra potential.

If you add more panels, add more SCC's to capture all potential yield. Overpaneling leads to clipping, which is not harvest of potential yield.

Refer to this post. https://diysolarforum.com/threads/eg4-6000xp-released-ordered-lets-go.71306/post-906494 It is a waste of resources.

 

[Texas-Mark]

For a given number of panels, there will not be any extra potential.

Of course there won't be, but that is not what was being discussed. Again, you asked: "Where does the mysterious extra PV energy come from due to overpaneling?" The answer is - the extra panels. Or are you claiming any clipping will always be more than the extra yield off peak (or on cloudy days)?

 

[Zwy]

You over-panel in parallel, not in series.

So there's no danger of going over the max PV voltage ratings, you just over produce current on a typical sunny/summer day and then on a cloudy/winter day you meet your ratings.

Did you read the links provided? Do you understand the following: why not harvest any potential yield and put it either in battery storage or a dump load?

I look at it this way, I size an array according to needed generation of potential yield to power loads and provide sufficient power to charge my storage. Any time there is potential for production, I want to harvest all of that yield. The argument made by members like yourself is due to not having enough storage for the energy harvested. I run 8.4Kw of PV, yet I manage to go 5 days with no sun running my house basically off grid. It is due to storage size, not the amount of PV. I harvest any potential yield at any time.

I think some of this myth came down from days of lead acid storage, where battery banks needed to be charged thru absorption on a regular basis (daily) in order to lengthen service life of the battery bank. LFP on the other hand prefers running in the middle and works perfectly not reaching full SOC daily. It does not matter if full charge is ever reached on a regular basis, one could go for months (we see some members reporting they finally reached full SOC since November) and not reach full SOC. Why would you overpanel if you have the storage available and all you need is another SCC to harvest any potential? The array cost the same whether you harvest part of the yield (clipping) or all of the yield.

Some of you just might catch on to the concept.

 

[Zwy]

Of course there won't be, but that is not what was being discussed. Again, you asked: "Where does the mysterious extra PV energy come from due to overpaneling?" The answer is - the extra panels. Or are you claiming any clipping will always be more than the extra yield off peak (or on cloudy days)?

Yes, you are stuck in that mindset or trying to deflect from a losing position.

I don't know which, but the excuse of adding more panels is an old argument that doesn't hold water. Read the response above, it might sink in or it may not.

I don't subscribe to the mistaken theory that clipping and overpaneling with X number of panels leads to increased yield compared to underpaneling a SCC. It is ludicrous.

 

[Texas-Mark]

why not harvest any potential yield and put it either in battery storage or a dump load?

Not everyone is using a battery system. Then there is the added cost of them.

 

[Bop]

Overpanelng doesn't lead to more production- IN GOOD CONDITIONS...

If however you are in a location where bad weather is common, then yes, over paneling can give you more generating ability in those poor conditions- safely...

With offgridding, when you have a certain battery capacity- you also have a maximum safe charging level (which varies according to chemistry and type) so if you add extra charge controllers to avoid 'over paneling' then in good conditions you can be overcharging your battery bank in good conditions (as in too much current, not voltage) and this leads to premature battery bank failure and short service life...

(look at your battery/cell specifications- there will be on any decent brand a 'maximum charge current' listed- exceeding this is 'bad, m'kay')
In this case the 'clipping' found in overpaneling is a 'good thing' it allows the battery bank to remain within its safe charge current limits in good weather conditions- AND- make use of the extra panel output in poor weather conditions... automatically...

If you had put in more charge capacity in the charge controllers to avoid over paneling, then you would be down to manually checking the charge current in good weather conditions and manually switching off some arrays to bring the charge current back to the safe working limits of your battery bank- until you forget, or aren't home, then 'lets start cooking that battery bank'...

These are my personal cells specs- look down about halfway- see the 'maximum charge current'- thats the one that is important in this case, but for those who have common overcast conditions for extended periods, overpaneling can have your daily kwh in total still up in a usable amount- without the charge controllers overcurrenting the battery bank in good weather conditions ...
Win/win...

Of course overpaneling isn't 'required' in gridtie systems- at worst it costs you a few more dollars in lost production and usage from the grid, but thats not really an issue apart from hurting your wallet...
(and even then, slight overpanneling is common on gridties here- a single phase house is limited to 5kw of gridtie inverter, but the older ssystems had 6kw of PV array, newer ones are 6.6kw and some even 7kw, still on that same 5kw inverter limit...)

 

[Zwy]

Not everyone is using a battery system. Then there is the added cost of them.

Gird tie is even better as storage is unlimited.

Try again?

 

[Andrewr05]

Aren't panels cheaper than another 1-2kW of batteries?

In a perfect world, yes, you would want to have the battery capacity to take in every square inch of your yards solar availability.

But if you've already sized your battery to what you want/need or that's what you can afford at the moment, then why add more capacity if you don't need to.

You're netting the same results either way.

Either you further oversize your battery storage to last through events of lessened solar production.
OR
You further oversize your solar array so that on any given day, no matter what (within reason), you are always collecting the amount of solar power necessary.

 

[Texas-Mark]

If however you are in a location where bad weather is common, then yes, over paneling can give you more generating ability in those poor conditions- safely...

Yes, someone actually gets it.

 

[Texas-Mark]

Either you further oversize your battery storage to last through events of lessened solar production.
OR
You further oversize your solar array so that on any given day, no matter what (within reason), you are always collecting the amount of solar power necessary.

Hey, lets not interject logic into this tread.

 

[Bop]

Yes, someone actually gets it.

Should do- been in the solar game for four decades LOL- if I didn't get it by now, I never would...
Some others however seem determined to 'not get it' (while accusing others of being 'stuck in a mindset')

 

[Zwy]

Overpanelng doesn't lead to more production- IN GOOD CONDITIONS...

If however you are in a location where bad weather is common, then yes, over paneling can give you more generating ability in those poor conditions- safely...

X number of panels only have X potential yield.

Where do you source these magic panels that produce more yield just because you overpanel a SCC compared to underpaneling an SCC?

Does the panel morph into super yield production just because it is one string where the SCC is overpaneled?

Please share your source.

With offgridding, when you have a certain battery capacity- you also have a maximum safe charging level (which varies according to chemistry and type) so if you add extra charge controllers to avoid 'over paneling' then in good conditions you can be overcharging your battery bank in good conditions (as in too much current, not voltage) and this leads to premature battery bank failure and short service life...

Say what???

(look at your battery/cell specifications- there will be on any decent brand a 'maximum charge current' listed- exceeding this is 'bad, m'kay')
In this case the 'clipping' found in overpaneling is a 'good thing' it allows the battery bank to remain within its safe charge current limits in good weather conditions- AND- make use of the extra panel output in poor weather conditions... automatically...

Say what??

If you had put in more charge capacity in the charge controllers to avoid over paneling, then you would be down to manually checking the charge current in good weather conditions and manually switching off some arrays to bring the charge current back to the safe working limits of your battery bank- until you forget, or aren't home, then 'lets start cooking that battery bank'...

I never worry about charge current. I have a bank large enough that even if I had 120A of charge current, each 16S battery in a bank of 4 will only have 30A of charge current. 160A would be 40A.

I'm not anywhere even close to 1C.

These are my personal cells specs- look down about halfway- see the 'maximum charge current'- thats the one that is important in this case, but for those who have common overcast conditions for extended periods, overpaneling can have your daily kwh in total still up in a usable amount- without the charge controllers overcurrenting the battery bank in good weather conditions ...
Win/win...
View attachment 194890

3C? Really, you are using that spec as an argument?

1200A on just one 48V battery would take something like 60Kw of PV yield.

 

[Zwy]

Should do- been in the solar game for four decades LOL- if I didn't get it by now, I never would...
Some others however seem determined to 'not get it' (while accusing others of being 'stuck in a mindset')

I know I'm correct, you did the same thing for 4 decades and seem stuck in that mindset.

We have an industry saying, "40 years of experience or is it 40 years of the same experience?"

 

[Zwy]

Hey, lets not interject logic into this tread.

It's not needed with LFP and large battery banks.

How's that for logic?

 

[Andrewr05]

X number of panels only have X potential yield.

Where do you source these magic panels that produce more yield just because you overpanel a SCC compared to underpaneling an SCC?

Does the panel morph into super yield production just because it is one string where the SCC is overpaneled?

Not trying to be an asshole here, But I think that you just fundamentally do not understand what we are trying to say.

You've said the same thing like three or four times now and I legitimately think that you just aren't willing to be wrong. You are so stuck on the thought that you have to be right that you aren't stopping for like four and a half seconds to actually think about what you're typing and to comprehend what you're reading in a way that lets you actually pay attention to what we're saying.

 

[Texas-Mark]

X number of panels only have X potential yield.

Nobody is arguing that.

Where do you source these magic panels that produce more yield just because you overpanel a SCC compared to underpaneling an SCC?

If you don't understand that X+2 panels will produce more than X+0 panels off peak or when cloudy, then I don't know what to tell you.

 

[Zwy]

Aren't panels cheaper than another 1-2kW of batteries?

In a perfect world, yes, you would want to have the battery capacity to take in every square inch of your yards solar availability.

You will find over time, that you will want higher battery capacity for autonomy.

But if you've already sized your battery to what you want/need or that's what you can afford at the moment, then why add more capacity if you don't need to.

I usually hear this from those who do not have much storage. Storage comes in many forms, it is not just limited to batteries.

You're netting the same results either way.

I want to capture any potential yield my array can put out. I will find a use for any excess.

Either you further oversize your battery storage to last through events of lessened solar production.
OR
You further oversize your solar array so that on any given day, no matter what (within reason), you are always collecting the amount of solar power necessary.

Stretches here run commonly 6 days with very limited sun in winter.

Should I add to my array and overpanel the SCC's or add to battery storage? Which one provides the ROI?

1.2GW of array won't help if the sun doesn't shine. https://diysolarforum.com/threads/december-pv-starting-off-crappy-again.74081/post-973262 You might catch on.