Solar panels different voltages does it matter?

[olley]

Over 15 years ago I bought 2 Kyocera130w panels of Gromett, around 5 years ago I bought another from Ebay.
I decided to upgrade and removed the two older panels and have just finished in the instal of two 410w in their place, on checking the polarity the two new panels are showing 32v, the single older 120w is showing 19v, is there any point in connecting it? Lenny HB

 

[Jev88]

I "think" your bigger panel will be pulled down to the smaller panel capability.

 

[Lenny HB]

Over 15 years ago I bought 2 Kyocera130w panels of Gromett, around 5 years ago I bought another from Ebay.
I decided to upgrade and removed the two older panels and have just finished in the instal of two 410w in their place, on checking the polarity the two new panels are showing 32v, the single older 120w is showing 19v, is there any point in connecting it? Lenny HB

No, you can't connect those in parallel, if you want to use the older one connect it via a separate controller.

 

[olley]

Thanks guys how about I buy another 120watt and connect in series with the other one giving 38v, could I connect it then?

 

[Lenny HB]

Thanks guys how about I buy another 120watt and connect in series with the other one giving 38v, could I connect it then?

Nomally the off load voltage of 12 v panels is between 21v to 24 v I wouldn't connect panels with more ½ v difference.
So the answer is no

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[Raul]

Count the cells on the new panel. I expect 120 half cut for 400w. That would be 60 cell in parallel, with cables in the middle.
If two old panels are close to the new panel cell count, then you can series connect two old then parallel with the new.

 

[Ditcha]

Thanks guys how about I buy another 120watt and connect in series with the other one giving 38v, could I connect it then?

If you connect the 2x 120w in series to give you 38v @ 120w when you then connect these to your 2x 410w in parallel which will give you 32v @ 820w try it and see but I would think the smaller panels would pull the larger down to 120w.

 

[Raul]

If you connect the 2x 120w in series to give you 38v @ 120w when you then connect these to your 2x 410w in parallel which will give you 32v @ 820w try it and see but I would think the smaller panels would pull the larger down to 120w.

No it wont, how can it pull it to 120w? We talking volts here

 

[olley]

Count the cells on the new panel. I expect 120 half cut for 400w. That would be 60 cell in parallel, with cables in the middle.
If two old panels are close to the new panel cell count, then you can series connect two old then parallel with the new.

6 rows of 18= 104cells
After a bit of googling it appears that at 32v the difference between PWM and MPPT becomes much more marked, so I think instead of messing around trying to get the old panel into the system, I would be better of spending the money on a new MPPT controller, and just remove the old one off the roof. it can join its older brethren.

 

[Ditcha]

No it wont, how can it pull it to 120w? We talking volts here

The two 410w panels will be pulled down to 120w each if the 2 120w panels are connected in series then in parallel to the 410w panels as per question asked in post #4.

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[Ditcha]

This might explain it better than I can,

Using Mismatched Solar Panel Sizes in the Same Array

This blog post will teach you how using mixed and mismatched sizes of solar panels in the same array will affect the output of the entire array.

explorist.life

 

[Raul]

6 rows of 18= 104cellsView attachment 774438
After a bit of googling it appears that at 32v the difference between PWM and MPPT becomes much more marked, so I think instead of messing around trying to get the old panel into the system, I would be better of spending the money on a new MPPT controller, and just remove the old one off the roof. it can join its older brethren.

I wouldn’t even dare put that one on pwm. The voc is 37voc, so the operating voltage can be anywhere between 30 to 37v or even higher in cold weather.
As Lenny says, wallet out and another MPPT for the new ones.

 

[olley]

Just ordered a Renogy 60amp MPPT

 

[Ditcha]

If you connect the 2x 120w in series to give you 38v @ 120w 240w when you then connect these to your 2x 410w in parallel which will give you 32v @ 820w try it and see but I would think the smaller panels would pull the larger down to 120w 240w

The two 410w panels will be pulled down to 120w 240w each if the 2 120w panels are connected in series then in parallel to the 410w panels as per question asked in post #4.

120w should be 240w in above calculations my mistake