Mix pv strings - Again

fca1

Hi i have 2 pv arrays one of 4 strings of 3 panels in parallel and other of 3 parallel strings of 2 panels.
i have array 1 connected to a morning star mppt60 and the other to a midnite150 .
i want to add a 3º array and because of that i want to join these 2 arrays to only 1 CC the midinite 150.

My String volts difference are very close 4.8v in voc and 2.8v in vmp.... very close....
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Give me a help here will i loose me too much joining the 2 arrays ? its possible to at least in theory to calculate the possible losses...

thanks

Cariboocoot

Re: Mix pv strings - Again

Let's see if I've got this right.
One array has a Vmp of 92 and one has a Vmp of 95? Not enough difference there to worry about.
The controller will pick its own Imp*Vmp and you won't see any noticeable power loss as opposed to running them separately. In fact you may see a gain as there would be one less controller pulling power.

I've been working on mismatched array issues recently. It's amazing how well different Vmp's get along on an MPPT controller providing the Voltage and Watts aren't so far off that it pulls one array above its Vmp causing severe current drop-off. It's also very hard to predict in advance just what Voltage the controller will pick, especially as it changes through the day.

fca1

Re: Mix pv strings - Again

Done midnite 150 upgraded to latest firmware ... Combiner box near the CC and both arrays connected to the midnite ...
Now is waiting to sun to rise
I had much better results with the Morningstar mppt60 then with the midnite, let's hope that the new firmware will help ...

I will post results later on ..

fca1

Re: Mix pv strings - Again

First day with both arrays on midnite... still feeling that morningstar has some.... i don't know
I will let it on Midnite for a few days and change to the MPPT60 even that is bit higher than the 60Amps of mppt60...

so yesterday 2 arrays 2 CC
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Today 2 arrays one CC midnite
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more info....
pvamps vs pvvolts
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bat temperature
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fet temp
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Watts
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