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Different solar panels in series


Zimbo
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Greetings

I am very aware of the advice that solar panels with different power ratings should not be connected together. It is  said that doing so would result in the other panel/s only providing as much power as the lowest rated panel.

When I looked at the specs of a 275w and a 330w panel from the same manufacturer  I noted that the mppt current and short circuit current from each was very similar. The main difference is that the more powerful panel has a higher mppt voltage.

I wonder whether this means that if these two panels are connected in series the output would be a little less than 275+330=605w (limited by the mppt current of the slightly lower one) but more than 275+275=550w.

Have any of you tried something like this? 

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Thanks Vassen

The panels in question are a Jinko "Eagle" with 60 cells (6 x 10), 275Wp poly crystalline panel with Imp = 8.61 Amps

in series with a Jinko "Eagle" with 72cells (6x12), 330Wp poly crystalline panels Imp = 8.66 Amps.

 

Yes the Imp of each are close and I would expect the combination to have an Imp around 8.61 Amps.

Both are poly crystalline but the larger one needs more cells to yield the power. That makes it a bit longer but the same width.

I had assumed that with that cell configuration it would be OK to mix the 60 cell panel with the 72 cell panel. Maybe I am wrong.

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8 hours ago, Zimbo said:

Thanks Vassen

The panels in question are a Jinko "Eagle" with 60 cells (6 x 10), 275Wp poly crystalline panel with Imp = 8.61 Amps

in series with a Jinko "Eagle" with 72cells (6x12), 330Wp poly crystalline panels Imp = 8.66 Amps.

 

Yes the Imp of each are close and I would expect the combination to have an Imp around 8.61 Amps.

Both are poly crystalline but the larger one needs more cells to yield the power. That makes it a bit longer but the same width.

I had assumed that with that cell configuration it would be OK to mix the 60 cell panel with the 72 cell panel. Maybe I am wrong.

 

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...I am referring to a 72 cell panel in series with a 60 cell panel from the same manufacturer.

Yes, to connect a 72 cell panel in parallel with a 60 cell panel is unlikely to make sense because of the voltage difference between them

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2 hours ago, Zimbo said:

...I am referring to a 72 cell panel in series with a 60 cell panel from the same manufacturer.

Yes, to connect a 72 cell panel in parallel with a 60 cell panel is unlikely to make sense because of the voltage difference between them

there is no reason why 72 cell panel in series or parallel with a 60 cell panel will not work. It is recommended that you do not mix different panels, but that does not mean they will not work. Recommendation are just that and it all depends on the user to follow them or not. Yours are even better because they are from the same manufacture and the current is closely matched. Your system will work 

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12 hours ago, Zimbo said:

I had assumed that with that cell configuration it would be OK to mix the 60 cell panel with the 72 cell panel.

I can't see any problems with that.

As long as your solar charge controller can handle the resultant voltage (not too high to blow it up and not too low to cause dropouts in low light).

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Yes. My inverter's charge controller is designed for an operating voltage of 30-80 v DC and a maximum Voc of 102V.

Interestingly my inverter's MPPT charge controller maximum current is given as 40 amps which to me means up to 6 panels if wired as three pairs of two in series then the three pairs paralleled. That is about 320 x 6 = 1.9kWp but the rated capacity is only 1kW (more or less the power of three 320Wp panels in parallel).

 Maybe they are playing it safe or the cooling system can only cope with 1 kw.

I plan to play it safe and stick to using no more than the "two pieces in serial and 2 sets in parallel". Because our roof does not face due north and the slope of our roof is not optimal that should give a maximum of around 1kW

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