Panel performance. 4s2p vs 8s

[eabyrd]

i have 8 identical panels. 250 watt. 37VOC. 30VMP. 8AMP (fractions truncated) currently running into a Victron Smartsolar 150/35 to charge a Bigbattery HSKY and run a Sigineer split phase 6kw inverter charger currently the panels are in a 4s2p configuration and max out at a bit over 1850 watts. Total production if I stay out of absorption or float is about 12k best I can tell.

i am strongly considering buying a MPP LVX 6048 which, among other improvements (intended for home use being primary) would allow me to run the string as an 8s1p configuration. I am not sure if I will be better able to limit the wasted capacity that comes with a full battery

There is partial shading in early to mid AM over 3 or 4 of the panels. The total wire run through 10 gauge is less than 100 feet so I don’t think those losses are significant, but I could be wrong

would you think my peak power /overall production would go up, down, or remain essentially the same in the new configuration

looking forward to thoughts and perspectives

ed

 

[Diysolar123]

even a small amount of shade on a panel basically shuts the entire panel down...so the current from those panels will be near zero during any shading.
when it comes to solar panels "shade" == very bad!
I found a nice short video that shows why shading has such a large impact on power output.

If the panels are 100' from the charge controller thats 200' of wire; The 8S1P will keep the current low so thats a good thing, I would probably order some 8awg MC4 cables just in case you even decide to go with 8S2P, but thats just future proofing and not needed.

Your "power" will be mostly the same, you are saving some heat losses by cutting your current in half but power is power...
You may gain more power by trying to better manage your shade problem and possibly just re-orient your panels.

 

[eabyrd]

Thanks, and good advice re the shading, but this array is a hobby and to maintain wife’s blessing I must keep it out of her primary sight lines and I certainly can’t remove her favorite dogwood ? The shade is past by9:30 You raised another question that keeps nagging at me though. How “shaded” is shaded. There has to be some threshold that once passed kills the string, but overcast skies still give some power so it’s not full sun or nothing do you have any info on that?

also wondering if since the shading only hits the first 4 panels is the 2P configuration better then for morning performance or will the bypass diodes negate the difference there? Oh the unscientific experiments in my fire ?

 

[bladetoyshop]

Thanks, and good advice re the shading, but this array is a hobby and to maintain wife’s blessing I must keep it out of her primary sight lines and I certainly can’t remove her favorite dogwood ? The shade is past by9:30 You raised another question that keeps nagging at me though. How “shaded” is shaded. There has to be some threshold that once passed kills the string, but overcast skies still give some power so it’s not full sun or nothing do you have any info on that?

also wondering if since the shading only hits the first 4 panels is the 2P configuration better then for morning performance or will the bypass diodes negate the difference there? Oh the unscientific experiments in my fire ?

Well do I know the feeling of not wanting to (or being able to) cut down a tree; I have a similar issue with a very beautiful Butterfly Tree (aka Butterfly bush) near where I want to place my two solar arrays. I can put one array where it will get full sun, but the second one will be blocked during the morning hours, much as your panels will.

 

[MisterSandals]

I am not sure if I will be better able to limit the wasted capacity that comes with a full battery

There are a couple things you can do to limit excess solar energy.
The obvious thing is to get more battery capacity.
Other things include pointing part of your array east-ish and part west-ish to spread out your charging: this only helps if you have a use during this prolonged charging period.
Additionally, if you could run appliances (laundry, car charging, water heating ...) during peak solar.

Is your thought to sell power back to the grid with the LVX 6048? Power companies seem to make an effort to discourage helping them out by paying little for spinning the meter backwards and often have significant fees too. The grid makes an expensive battery.

 

[eabyrd]

even a small amount of shade on a panel basically shuts the entire panel down...so the current from those panels will be near zero during any shading.
when it comes to solar panels "shade" == very bad!
I found a nice short video that shows why shading has such a large impact on power output.

If the panels are 100' from the charge controller thats 200' of wire; The 8S1P will keep the current low so thats a good thing, I would probably order some 8awg MC4 cables just in case you even decide to go with 8S2P, but thats just future proofing and not needed.

Your "power" will be mostly the same, you are saving some heat losses by cutting your current in half but power is power...
You may gain more power by trying to better manage your shade problem and possibly just re-orient your panels.

Well do I know the feeling of not wanting to (or being able to) cut down a tree; I have a similar issue with a very beautiful Butterfly Tree (aka Butterfly bush) near where I want to place my two solar arrays. I can put one array where it will get full sun, but the second one will be blocked during the morning hours, much as your panels will.

 

[eabyrd]

Shadows are gone by 9:06 am so I think we’re ok this time of year. I continue to adjust to seasonal shifts. Yes, the dead spots are my fault before I raised the height of my PVC contrap

 

[eabyrd]

There are a couple things you can do to limit excess solar energy.
The obvious thing is to get more battery capacity.
Other things include pointing part of your array east-ish and part west-ish to spread out your charging: this only helps if you have a use during this prolonged charging period.
Additionally, if you could run appliances (laundry, car charging, water heating ...) during peak solar.

Is your thought to sell power back to the grid with the LVX 6048? Power companies seem to make an effort to discourage helping them out by paying little for spinning the meter backwards and often have significant fees too. The grid makes an expensive battery.

No desire to feed the grid. Too much hassle. This is more a hobby / learning experience than anything. I would like to get some bene too in lower bills and insurance from grid down situations. That’s how I am selling it to the ever patient lady who puts up with me anyway. I am starting today with a battery less charged. That will help too

 

[wattmatters]

How “shaded” is shaded. There has to be some threshold that once passed kills the string, but overcast skies still give some power so it’s not full sun or nothing do you have any info on that?

Cells in series are like a chain in that they are only as strong as the weakest link. So it's not a matter of shade being on/off but how much light is striking the shaded cells. This is what limits the current flowing through the cells placed in series.

Modern (larger) panels like yours have three groups of cells each with a bypass diode, so if one of those sections is shaded but the others are not, then the bypass diode for the shaded group of cells kicks in allowing current to flow around the shaded cells and through the other 2 groups of cells in the panel and you only lose about 1/3rd of that panel's output.

But once the shade begins to affect all three groups of cells, well that significantly compromises the current which can flow through that entire panel and this also limits the current which can flow through all other panels connected in series.

Shade looks and is worse in full sun because the light is mostly coming from a single point source - the Sun. The object casting the shade blocks most of the light hitting the cell. Obviously not all light since you can still see it (because of the light reflected from other objects and the diffusion of light in the atmosphere).

Overcast days however diffuse the Sun's light a lot and so photons strike the panel more evenly from many angles. That's why the array is less affected by where shadows would have been had the Sun's light not been already been obscured by cloud.

Conversely, when a cloud edge passes over and allows the Sun to strike the panels, this "edging" lens effect can actually focus more light onto the solar panels than when they are in full Sun and result is output (briefly) higher than peak panel rating.

 

[eabyrd]

Cells in series are like a chain in that they are only as strong as the weakest link. So it's not a matter of shade being on/off but how much light is striking the shaded cells. This is what limits the current flowing through the cells placed in series.

Modern (larger) panels like yours have three groups of cells each with a bypass diode, so if one of those sections is shaded but the others are not, then the bypass diode for the shaded group of cells kicks in allowing current to flow around the shaded cells and through the other 2 groups of cells in the panel and you only lose about 1/3rd of that panel's output.

But once the shade begins to affect all three groups of cells, well that significantly compromises the current which can flow through that entire panel and this also limits the current which can flow through all other panels connected in series.

Shade looks and is worse in full sun because the light is mostly coming from a single point source - the Sun. The object casting the shade blocks most of the light hitting the cell. Obviously not all light since you can still see it (because of the light reflected from other objects and the diffusion of light in the atmosphere).

Overcast days however diffuse the Sun's light a lot and so photons strike the panel more evenly from many angles. That's why the array is less affected by where shadows would have been had the Sun's light not been already been obscured by cloud.

Conversely, when a cloud edge passes over and allows the Sun to strike the panels, this "edging" lens effect can actually focus more light onto the solar panels than when they are in full Sun and result is output (briefly) higher than peak panel rating.

Thank you for that explanation