Paralleling 480w and 580w 156 cell panels - 1v difference?

[hwy17]

I am building an 8s string of Q Cells 480w this year. I have already purchased those panels.

Later, I will probably want to expand. And I would like to double up to 2x 8s parallel.

Do you think the q cells 580w would parallel well with the 480w if both are 156 cell?

Voltages are within 1v of each other, like VOC 53.56/53.39 and VMP 45.33/44.88.

 

[yodamota]

sounds close enough to me. I suppose one is larger cells?

 

[hwy17]

sounds close enough to me. I suppose one is larger cells?

Yeah. Larger overall panel. They haven't really hit the US market yet but I'm figuring by the time I get around it it they might. And EG4 sells those brightmount extensions now to accommodate them.

 

[Mattb4]

With that much of a difference in wattage between the parallel strings I would want to go to a separate SCC and arrays for each. Not saying it would not work mind you.

 

[AntronX]

You should be fine. I would verify each string power output in full sun when both are parallel.

 

[Rocketman]

Let’s figure out the penalty by combining the two different solar panel strings in parallel. (I used math for the Imp - is it right?)

String1 - 8s of 480w Voc 53.56 Vmp 45.33 Imp 10.58a so string1 will have a Voc of 428v (I assume that voltage is ok for your charge controller with it rising in the winter).
Vmp 362 - Imp 10.58 - watts 3829w

String2 8s of 580w Voc 53.38 Vmp 44.88 Imp 12.92.
Vmp 359 Imp 12.92 - watts 4638

If you combine the two strings in parallel the amps add - but use the lower volts so:
V 359v Amps 23.5 - watts 8436

So if if separate SCC watts would be - 3829 + 4638 = 8467

Your penalty is 31 watts. (You can probably live with that).

I like to know the actual penalty- not just say they are close - so it is good.

 

[hwy17]

Let’s figure out the penalty by combining the two different solar panel strings in parallel. (I used math for the Imp - is it right?)

String1 - 8s of 480w Voc 53.56 Vmp 45.33 Imp 10.58a so string1 will have a Voc of 428v (I assume that voltage is ok for your charge controller with it rising in the winter).
Vmp 362 - Imp 10.58 - watts 3829w

String2 8s of 580w Voc 53.38 Vmp 44.88 Imp 12.92.
Vmp 359 Imp 12.92 - watts 4638

If you combine the two strings in parallel the amps add - but use the lower volts so:
V 359v Amps 23.5 - watts 8436

So if if separate SCC watts would be - 3829 + 4638 = 8467

Your penalty is 31 watts. (You can probably live with that).

I like to know the actual penalty- not just say they are close - so it is good.

That's great, thank you. I wasn't sure if it worked like that.

 

[sunshine_eggo]

It mostly works like that. That's your MAX penalty. If the higher voltage array is also higher power, the MPP may be a little bit above the lower string Vmp.

For all intents and purposes, those panels are "identical" with regards to Vmp. There is often more variation due to manufacturing tolerances than the 0.17V difference in Vmp.