Number of panels per string

[AmateurSolarBuild]

I have these panels:

Preorder - BlueSun 460W Half-Cell Bifacial Solar Panel (Silver) | Up to 575W with Bifacial Gain

Signature Solar provides solar panels, off-grid solar systems, grid-tie, and hybrid systems. Quality solar inverters, bifacial solar panels, complete solar kits, solar batteries. Featuring brands such as EG4 Electronics with their solar battery, LifePower4 and EG4 LLifePower4 and EG4 LL

signaturesolar.com

My two EG4 6500ex inverters will take 4 strings of panels in series and has a max PV input of 4000 watts per string. Max VOC is 500 volts per string.

I'm wanting to connect 8 panels on a single string. Those calculations are:

460 watts per panel * 8 panels = 3680 watts
50.8 VOC * 8 Panels = 406.4 VOC

By those numbers I should be good. My question is on the bifacial gain (they will be on a pergola on a deck), which can spike up to 575 watts.
575 * 8 = 4600 watts.

At that point I am over the max wattage. Is this a safe amount of over-paneling, or should I limit the string to 6 panels?

 

[rodrick]

max voltage adjusted for lowest temperature is a hard limit do not exceed it

watts are not, over paneling is common look at your scc specs for this but typically 25 to 50% is common in a lot of systems

 

[Tomthumb62]

I have these panels:

Preorder - BlueSun 460W Half-Cell Bifacial Solar Panel (Silver) | Up to 575W with Bifacial Gain

Signature Solar provides solar panels, off-grid solar systems, grid-tie, and hybrid systems. Quality solar inverters, bifacial solar panels, complete solar kits, solar batteries. Featuring brands such as EG4 Electronics with their solar battery, LifePower4 and EG4 LLifePower4 and EG4 LL

signaturesolar.com

My two EG4 6500ex inverters will take 4 strings of panels in series and has a max PV input of 4000 watts per string. Max VOC is 500 volts per string.

I'm wanting to connect 8 panels on a single string. Those calculations are:

460 watts per panel * 8 panels = 3680 watts
50.8 VOC * 8 Panels = 406.4 VOC

By those numbers I should be good. My question is on the bifacial gain (they will be on a pergola on a deck), which can spike up to 575 watts.
575 * 8 = 4600 watts.

At that point I am over the max wattage. Is this a safe amount of over-paneling, or should I limit the string to 6 panels?

I guess I don't understand how bifacial panels work. But since the Voc is listed at 50.8V, I assume that is the only number you need to be concerned with. Not sure how the backside plays in, unless it's in parallel with the front side.

So, yes, even at -20F (-29C), you'd get a max voltage of from 8 panels in series of 463V, so you're good there. Even at -50F (-46C), you're only at 481V, which is getting close, but it's not until you get to like -90F that you'd be in trouble. How cold is the coldest recorded temperature in your area?

 

[AmateurSolarBuild]

negative single digits Fahrenheit is the coldest I've ever seen here, so I should be good. Thanks.

 

[Tomthumb62]

negative single digits Fahrenheit is the coldest I've ever seen here, so I should be good. Thanks.

You don't want to go by "coldest I've seen here". Yes, global warming and all that, but if in 1977 a -40F was recorded in your area, you want to use that temp when configuring your series of panels. It may never in your lifetime reach that cold ever again, but since it happened once, there is a small possibility it could happen again. I guess it depends on how you like to gamble and how much money you can burn if you start frying MPPT's (especially if they are AIO's).

 

[Tomthumb62]

negative single digits Fahrenheit is the coldest I've ever seen here, so I should be good. Thanks.

This is a good calculator to use to figure how many panels in series with temp consideration to not go over your max V for your MPPT:

Solar Panel Maximum Voltage Calculator - Footprint Hero

Calculate the maximum open circuit voltage of your solar array. Find your max solar panel voltage to correctly size your solar charge controller.

footprinthero.com

 

[EastTexCowboy]

I guess I don't understand how bifacial panels work. But since the Voc is listed at 50.8V, I assume that is the only number you need to be concerned with. Not sure how the backside plays in, unless it's in parallel with the front side.

So, yes, even at -20F (-29C), you'd get a max voltage of from 8 panels in series of 463V, so you're good there. Even at -50F (-46C), you're only at 481V, which is getting close, but it's not until you get to like -90F that you'd be in trouble. How cold is the coldest recorded temperature in your area?

I'm not sure how that works on bifacial panels either but if they're rating it to spike from 460w to 575w either the current is increasing or the voltage is increasing. Doing a little bit of Googling it looks like the VOC listed on bifacial panels includes any spikes from the bifacial part. But that's just anecdotal from some comments. Maybe someone here can confirm.

 

[AmateurSolarBuild]

Well this is kind of a bummer. Looks like Signature Solar/EG4 will not warranty if you exceed the max wattage. So I will have to play it safe and stick to 6 panels per string :-/.

Putting more than 8kw on an EG4 6500ex

This question comes up a decent amount, since the mppt is power-limiting what would be the harm with using more solar, like 12kw on a single 6500w unit if you have it? The units will initially work alright if you keep the VOC limit minded, you could use 30kw and you would work fine for a good...

diysolarforum.com

 

[Tomthumb62]

Well this is kind of a bummer. Looks like Signature Solar/EG4 will not warranty if you exceed the max wattage. So I will have to play it safe and stick to 6 panels per string :-/.

Putting more than 8kw on an EG4 6500ex

This question comes up a decent amount, since the mppt is power-limiting what would be the harm with using more solar, like 12kw on a single 6500w unit if you have it? The units will initially work alright if you keep the VOC limit minded, you could use 30kw and you would work fine for a good...

diysolarforum.com

Your SCC will last longer by not overpaneling. Not sure how the AIO's work, if one component dies, can it be replaced or do you have to replace the entire AIO?

 

[AmateurSolarBuild]

Yeah, I think you have to ship the whole unit back on your own dime. Then they either fix or replace from there. 5 year warranty since I'm using their batteries. I did post in that thread. If I look at STC numbers I should be still good. Hopefully, James from Signature Solar can clarify if those STC numbers are affected by the bifacial gain.

 

[ksmithaz1]

Well this is kind of a bummer. Looks like Signature Solar/EG4 will not warranty if you exceed the max wattage. So I will have to play it safe and stick to 6 panels per string :-/.

Putting more than 8kw on an EG4 6500ex

This question comes up a decent amount, since the mppt is power-limiting what would be the harm with using more solar, like 12kw on a single 6500w unit if you have it? The units will initially work alright if you keep the VOC limit minded, you could use 30kw and you would work fine for a good...

diysolarforum.com

The listed voltage limits on the panels are hard limits. The voltage will go down somewhat as you draw, but will not exceed VOC, other than the normal temperature variances, ie if it gets cold voc goes up a bit. If you don't get the sunshine you won't get as many available amps. The amount of amps you draw is based on the load, which is controlled by the MPPT, and whatever the MPPT is feeding electrons to. Frankly, if the MPPT allows a greater current draw than it is capable of handling I would consider it broken, but some of this stuff is kind of sketchy. Also you will never draw more current from your panels than whatever your loads require, but do keep in mind, some conversion loss, and you might be driving a load on the inverter as well as charging the batteries. Max battery charge rates are generally settable, thus I'm having a hard time with overpaneling causing any issues, unless you are running your system right on the edge.

Lastly, I have 32 brand new 455w panels on my roof in a 4x8, I'm in Phoenix, and I saw clouds today. Nowhere near me, but I saw them in the East! (Supposed to actually rain tomorrow night) Theoretically I should be able to get 3640 watts from the panels. The best I've seen is around 2900 (~78%) , so don't hold your breath on ever seeing 4600 watts. I picked up 16 fairly old CS250's used for next to nothing. I have them in two strings, best I've seen there is ~2700W (~67%). If you want to run a single string of 8 I think you are probably fine, unless you are cranking the inverters and charging the batteries at max, and we are having a solar bonus day, and your MPPT's don't have any current limiting.