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Which voltage number in solar panel specs...

Wesubi

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Which voltage number in solar panel specs is used to determine the proper MPPT size when panels are in series? Open circuit voltage, optimum operating voltage, etc,?

Thank you !
 
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Voc is used to determine the maximal limit your equipment can handle.
Vmp is used to determine how much power you are making.

Let's say you buy four 30V panels. Their Vmp is 30.0V, and the Voc is 37.5V. With a 100V controller, you could only wire them in a 2S2P configuration. 37.5V + 37.5V=75Voc. You can not wire 3 or 4 in series because their voltages would be 112.5V and 150V. 3 panels could be safely wired if your controller could handle 150V, and 4 is it could handle 200V.
 
Which voltage number in solar panel specs is used to determine the proper MPPT size when panels are in series? Open circuit voltage, optimum operating voltage, etc,?

Thank you !
Do you have some panels you want to configure or is this only a theoretical question?
 
Do you have some panels you want to configure or is this only a theoretical question?
Thank you. Researching different options at this point. With this information it looks like I can use three Merlin panels, 175 Watt, 31 ish VOC along with a victron 100 / 30 and be okay.
 
Thank you. Researching different options at this point. With this information it looks like I can use three Merlin panels, 175 Watt, 31 ish VOC along with a victron 100 / 30 and be okay.
Maybe not ok.
31ishVoc x 3 panels in Series is about 94V
94V x 1.1 for 32°F temp compensation is 103V which is over the Victrons 100V max input.
So how cold does it get at your location?
Colder than 32 will raise the voltage more.

175w x 3 is 525 watts is about 40A into a 12V battery so a 30A SCC would be overpaneled.

This is why asking generalized questions without specifics on your system is a bad idea.

What battery do you have?
 
Maybe not ok.
31ishVoc x 3 panels in Series is about 94V
94V x 1.1 for 32°F temp compensation is 103V which is over the Victrons 100V max input.
So how cold does it get at your location?
Colder than 32 will raise the voltage more.

175w x 3 is 525 watts is about 40A into a 12V battery so a 30A SCC would be overpaneled.

This is why asking generalized questions without specifics on your system is a bad idea.

What battery do you have?
Lifepo4 560ah. Solar panel seller just wrote in response to questions:
"1) You will need a larger controller if you use (3) 220 watt panels. @ 660 Watts @ 12V you need the 150/60 or the or 150/70. The 150/45 might be a little low on a super clear day that is cold.

2) If you run in series then 10 AWG or 8 AWG wire is fine.

3) Yes I would fuse the solar side also."

I didn't realize I need to add watts together in series. Clearer now.
Running 4/0 wire to Inverter/charger.
 
Lifepo4 560ah. Solar panel seller just wrote in response to questions:
"1) You will need a larger controller if you use (3) 220 watt panels. @ 660 Watts @ 12V you need the 150/60 or the or 150/70. The 150/45 might be a little low on a super clear day that is cold.

2) If you run in series then 10 AWG or 8 AWG wire is fine.

3) Yes I would fuse the solar side also."

I didn't realize I need to add watts together in series. Clearer now.
Running 4/0 wire to Inverter/charger.
Be mindful, the length of wire and carrying current req are the key factor of the wire size. You don't want to undersize your wire size. When you pick the fuse for the panel, make sure it's compatible with your panel name plate and how you install them is crucial too.
 
Be mindful, the length of wire and carrying current req are the key factor of the wire size. You don't want to undersize your wire size. When you pick the fuse for the panel, make sure it's compatible with your panel name plate and how you install them is crucial too.
3 panels in Series do not need a fuse.
 
Lifepo4 560ah. Solar panel seller just wrote in response to questions:
"1) You will need a larger controller if you use (3) 220 watt panels. @ 660 Watts @ 12V you need the 150/60 or the or 150/70. The 150/45 might be a little low on a super clear day that is cold.

2) If you run in series then 10 AWG or 8 AWG wire is fine.

3) Yes I would fuse the solar side also."

I didn't realize I need to add watts together in series. Clearer now.
Running 4/0 wire to Inverter/charger.
You add the watts of the panels no matter how they are connected.
3 panels in Series do not need a fuse.

Using a 150V max input SCC will be ok with 3 panels in Series unless the Voc is close to 50V

Doesn't Victron make a 150 / 50A SCC?
 
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