Hello! I have 9 panels on my roof that fit my inverter perfectly
I could have a change to buy 9 identical panels in the near future and I'm thinking about installing them under the existing ones in 9s2p configuration (I mean, two 9s strings connected to the same mppt tracker in parallel)

But my existing installation gets a long shadow from smoke stacks for the whole morning, severely capping my early production
Second string should be not affected by it, or affected for much less time

So, considering that second string could theoretically start producing much earlier -- do I need any additional hardware between parallel strings?
Maybe some diodes?
Or will it not be affected by shadowed top string at all?

Thank you!

Paraphrasing a reply I've got on another forum:
Shaded panels will create high enough voltage to prevent backfeeding from irradiated panels without any additional hardware
So it's fine 🙂

On 2024/07/05 at 1:25 PM, WallK said:

Hello! I have 9 panels on my roof that fit my inverter perfectly
I could have a change to buy 9 identical panels in the near future and I'm thinking about installing them under the existing ones in 9s2p configuration (I mean, two 9s strings connected to the same mppt tracker in parallel)

Make and model of Inverter?

Existing panel spesifications?

The inverter mppt input spesifications will indicate if you can safely add 9 panels in 2p configuration. Each panel has seperate bypass diodes so yes for the shading part you don't need any external hardware but important to note that shading for a series string does have a big impact on power generation.

Edited July 10, 20242 yr by TaliaB

On 2024/07/10 at 10:14 AM, TaliaB said:

Make and model of Inverter?

Existing panel spesifications?

The inverter mppt input spesifications will indicate if you can safely add 9 panels in 2p configuration. Each panel has seperate bypass diodes so yes for the shading part you don't need any external hardware but important to note that shading for a series string does have a big impact on power generation.

MPPSolar PIP6048MT (Axpert VM III Twin)

Panel specs (all the panels are the same):
Peak Power Watts-PMAX (Wp)             565

Maximum Power Voltage-VMPP (V)      38.3
Maximum Power Current-IMPP (A)       14.76
Open Circuit Voltage-VOC (V)               45.6
Short Circuit Current-ISC (A)                 15.81

I think I'm cutting it pretty close to the tracker's limits 🙂

Edited July 12, 20242 yr by WallK

39 minutes ago, WallK said:

I think I'm cutting it pretty close to the tracker's limits

Yes indeed if i am not mistaken the max input current of the VMIII Twin is 27A and with 2P you will be 2.52A over the manufacturer spesification, but you should be ok on that margin the array won't spend much time at Imp in any case. The tracker should clip the access current should it be necessary.

On 2024/07/12 at 10:01 PM, WallK said:

MPPSolar PIP6048MT (Axpert VM III Twin)

None of the VM models can be paralleled. They come with half-sized flash; no room for all the paralleling logic.

On 2024/07/12 at 3:47 PM, TaliaB said:

Yes indeed if i am not mistaken the max input current of the VMIII Twin is 27A and with 2P you will be 2.52A over the manufacturer spesification, but you should be ok on that margin the array won't spend much time at Imp in any case. The tracker should clip the access current should it be necessary.

That's my hope, it's not very over spec for the tracker not to be able to clip
Also, I just don't have anywhere to put all the energy when sun is shining high, this oversizing is more for winter
I think our power situation will be even worse then

3 hours ago, Coulomb said:

None of the VM models can be paralleled. They come with half-sized flash; no room for all the paralleling logic.

Yeah, that's a shame...
But I don't plan to parallel the inverters (I would love to, but alas), only the panels

On 2024/07/15 at 3:53 PM, WallK said:

But I don't plan to parallel the inverters (I would love to, but alas), only the panels

Oops! Pardon me for not reading the post properly.