Solar panel mixing help

[YahwehisKing]

Oooooooohhhkkk

Got a little shit stew to brew... lol

I currently have a solar array of 5s3p made with renogy 100watt panels. I just received 6 240 panels.

All renogy panels are model 100D SS
Though the most recent string of 5 have different stats than the other 2 strings.

Stats are as followed
2 strings of renogy 100DSS
@ VOC 21.6
VMP 17.9
IMP 5.72
1 string of renogy 100DSS
@ VOC 24.3
VMP 20.4
IMP 4.91

The panels I want to add are
Sharp 240watt(brand)
@ VOC 37.4
VMP 30.1
IMP 7.96

Also note I'm using a growatt 48v with a max voc input of 145v and a starting charge voltage of 60v

I was thinking of doing the 5s3p con fig and then config the sharp panels in 2s3p and connect it all parallel, would I write that as 5s2s6p lol

The voc for the 240 watt panels would be 74.8 at100% eff but that would bring down the 5s configs to 3/5th eff right??

So would I wire the sharp panels in a 3s to make the voc 112.2v matching closer to the 108.2v of the 2 5s strings and 121.5 of the other 5s string. If the VOC is similar does it matter that the 3s string of 240 would be 720watts when the 5s string is only 500?????

Thankyou for any help offered

 

[sunshine_eggo]

Oooooooohhhkkk

Got a little shit stew to brew... lol

I currently have a solar array of 5s3p made with renogy 100watt panels. I just received 6 240 panels.

All renogy panels are model 100D SS
Though the most recent string of 5 have different stats than the other 2 strings.

Stats are as followed
2 strings of renogy 100DSS
@ VOC 21.6
VMP 17.9
IMP 5.72
1 string of renogy 100DSS
@ VOC 24.3
VMP 20.4
IMP 4.91

The panels I want to add are
Sharp 240watt(brand)
@ VOC 37.4
VMP 30.1
IMP 7.96

Strings in parallel need to have very similar Vmp values - typically within about 10%. This will impose a 5-10% penalty to all "mismatched" strings.

Your 100W panels already have a relatively poor match - about 14%.

2S on the 240W is just right out. The Vmp of your other strings would be ABOVE the Voc of your Sharp string and that would cause the higher voltage arrays to just dump their current into the sharp string never sending anything into your.

You would need to go 3S on the 240W:

2 strings (5S2P): 89.5Vmp
1 string (5S): 102Vmp
Sharp string (3S2P): 90.3Vmp

Your full 2440W array would see a 7-14% penalty due to the mismatches.

 

[sunshine_eggo]

The panels I want to add are
Sharp 240watt(brand)
@ VOC 37.4
VMP 30.1
IMP 7.96

The voc for the 240 watt panels would be 74.8 at100% eff but that would bring down the 5s configs to 3/5th eff right??

Voc is open circuit voltage, not 100%. That's the voltage of the panel with 0A flowing. As soon as loads are pulled and current flows, voltage approaches Vmp.

So in the context of 100% efficiency being max rated power, then this occurs at Vmp and Imp.

 

[YahwehisKing]

Strings in parallel need to have very similar Vmp values - typically within about 10%. This will impose a 5-10% penalty to all "mismatched" strings.

Your 100W panels already have a relatively poor match - about 14%.

2S on the 240W is just right out. The Vmp of your other strings would be ABOVE the Voc of your Sharp string and that would cause the higher voltage arrays to just dump their current into the sharp string never sending anything into your.

You would need to go 3S on the 240W:

2 strings (5S2P): 89.5Vmp
1 string (5S): 102Vmp
Sharp string (3S2P): 90.3Vmp

Your full 2440W array would see a 7-14% penalty due to the mismatches.

Shaaaaweeet 14% loss on 2440 array is still better than a 1500 array yeehaw

Yeah my whole problem was if the difference in wattage mattered. I had read somewhere that as long as the voltage was similar it didnt matter but just wasn't sure.

And thankyou for the clarification of VMP gives me a better understanding of why the max VOC of the controller.

Now am I correct that the voltage at the controller is going to be the lowest at 89.5? And at 20ft away a drop in voltage to about 84?
I'm a little concerned that the array won't work well in lower light conditions because the voltage won't reach the 60v start charge conditions on the controller, without ideal or optimal conditions

 

[sunshine_eggo]

Shaaaaweeet 14% loss on 2440 array is still better than a 1500 array yeehaw

Yeah my whole problem was if the difference in wattage mattered. I had read somewhere that as long as the voltage was similar it didnt matter but just wasn't sure.

And thankyou for the clarification of VMP gives me a better understanding of why the max VOC of the controller.

Now am I correct that the voltage at the controller is going to be the lowest at 89.5?

No. At 25°C, it's going to be between 89.5 and 102, but probably closer to 89.5V.

And at 20ft away a drop in voltage to about 84?

That's a 6% voltage drop over 20 feet. That feels excessive, but it's acceptable if it can't be avoided.

I'm a little concerned that the array won't work well in lower light conditions because the voltage won't reach the 60v start charge conditions on the controller, without ideal or optimal conditions

That wording implies Voc value, but based on the datasheet I found, it's a MPPT working range, 60-115V.

I would not see any concerns with an 84Vmp array maintaining 60V and above unless you're in Death Valley on the hottest day of the year.

 

[Hedges]

Where's the data and the math for voltage drop over wire? 5.5V drop in 20 feet??

With two I/V curves that are different wired in parallel, MPPT will find some halfway point that delivers max power.

I wonder how different that would be if those strings were oriented differently? When sun falls on one and the other only gets ambient light, The one with sun sets the I/V curve. unless the one without direct sun is the lower voltage string; it will weigh a bit heavier on the voltage.
Maybe multiple orientations is better than all identical, for differing string voltages. But I'm not sure.

 

[Rocketman]

In figuring out the Math of the panels I found a better way.

The math behind solar strings is:
In series Voltage (Vmp) adds - use the lowest amps (Imp).
In parallel amps add - use the lowest volts.

So string1 & string2. 5s Vmp 17.9 Imp 5.72
Gets 89.5v 5.72a

String3 5s Vmp 20.4 Imp 4.91
Gets 102v 4.91a

Combining those three strings
89.5v 16.35a (that makes 1463watts

New panels 2s3p Vmp 30.1v Imp 7.96
V60.2 23.88a (1437w as a stand alone string)

If you combine old and new in parallel
V 60.2v A 40.23a = 2421watts

I noticed a couple of things - you will have over 40amps of current on that wire - it better be a 8awg or 6awg.

I just realized a better way if your new panels are 3s2p you get:
V 90.3v 15.92a

Combining all strings now gets you
V 89.5v 32.27a gives 2888w

This is still over 30amps - so your wire better be 8awg.

The new Setup with the new array at 3s2p 2888w vs 2940 potential watts is AMAZING 52w penalty with three different kinds of panels. This is why you do the math! Almost no loss!

You could also add a separate solar charge controller and recover even more watts - or two controllers and recover all lost watts.

Hopefully my “typing” makes sense.

After I reread this string I realized @sunshine_eggo said the same thing.

Good Luck

 

[YahwehisKing]

No. At 25°C, it's going to be between 89.5 and 102, but probably closer to 89.5V.



That's a 6% voltage drop over 20 feet. That feels excessive, but it's acceptable if it can't be avoided.




That wording implies Voc value, but based on the datasheet I found, it's a MPPT working range, 60-115V.

I would not see any concerns with an 84Vmp array maintaining 60V and above unless you're in Death Valley on the hottest day of the year.

Sorry for such a late reply but I had a few things that reminded me of the post. I got everything set up and have since since seen 2600-2800watts coming in and that was amazing with the 2400expected amount. But I wanted to not something odd, I've been getting lately around 3100-3200watts from the array. How is that possible lol?

 

[sunshine_eggo]

In re-reading the post, I think I miscalculated or typo'd the 2440W. If you used all panels in the 5S2P/5S/3S2P config, that's 2940W.

Cold weather and cloud edging can cause panels to output more than rated.