Advice for a rookie on matching solar panels to inverter

[kinghappy]

Putting in my first solar system. This will be an off grid system about 3kw. I have the battery system together (i'm in the lithium business) and just purchased a mpp 3048 lv-mk inverter from Ian. So now panels. Looking at doing a 3s2p config. There is a local supplier and I'm looking at the Heliene 490w panels( 132HC M10 SL 490) . The voltages all seem right but the 6 panels have the ability, at full output, to exceed the controllers max current. Will the controller just limit the current to its max or will the slightly higher amps damage the controller. I obviously could just use 4 panels but would like to use 6. Just want to make sure I won't be damaging anything.


Update: wasn't paying attention on this. 3s2p would be only 20a current, so that should be fine.

 

[BentleyJ]

Those panels have a Voc of 46 volts. The inverter is rated for 145V Max. 3S is not going to work.

EDIT: The MPPT range on the inverter is 60 to 115V so the 2S3P configuration is perfect since Vmpp on the panels is 36.7V

Impp of the PV panels is only 10A so you could do a 2S3P configuration and still only be at 30A PV input to the inverter MPPT which is well below the 50A limit.

 

[Rednecktek]

If the inverter can only use say 2000w (as an example) and you connect up 3000w of panel, it'll only send 2kw to your system. Fortunately being over paneled just means it'll hit that 2k limit easier during cloudy or lower light conditions.

You'll leave power on the table in summer but have an easier time in winter.

 

[timselectric]

Also keep in mind that at 3p each string will require a fuse.

Actually, if I'm reading the panel specs correctly. Fusing isn't required until 4p.

 

[kinghappy]

Those panels have a Voc of 46 volts. The inverter is rated for 145V Max. 3S is not going to work.

EDIT: The MPPT range on the inverter is 60 to 115V so the 2S3P configuration is perfect since Vmpp on the panels is 36.7V

Impp of the PV panels is only 10A so you could do a 2S3P configuration and still only be at 30A PV input to the inverter MPPT which is well below the 50A limit.

46x 3 = 138v That is lower than 145v , so why won't they work?

 

[BentleyJ]

46x 3 = 138v That is lower than 145v , so why won't they work?

The datasheet specifies Voc values at Standard Test Conditions which is 25 deg. C. PV's are semiconductors and exhibit an inverse relationship to temperature. Translation, Voc goes up when temperature goes down. Your location is listed as Naples. Not sure which one but in either case there is Winter weather.

 

[740GLE]

what’s the record cold for your area?

Will the system be run year round or is it seasonal?

 

[kinghappy]

I'm in S. FL will be used year around.

 

[Rednecktek]

Actually, if I'm reading the panel specs correctly. Fusing isn't required until 4p.

Anything 3 or more needs fuses. When I did my 3s4p array I just grabbed a cimbiner box, it made things much easier.

46x 3 = 138v That is lower than 145v , so why won't they work?

Because when the sun comes up on that brisk winter morning and your panels are cold, the voltage could easily go over your limit. Remember, PV input is a HARD limit. Like makes diamonds look squishy hard, or Mother Superior with a ruler hard.

 

[timselectric]

Anything 3 or more needs fuses.

Not necessarily.
Usually it's the case, but not always.
You only need to fuse a string if there is more available current than it can safely handle.
In this case, the chosen panels are rated at 13.3a short circuit.
And maximum fuse rating of 30a.
13.3a x 2 = 26.6a
Which is below the 30a fuse rating.
So in this rare case, 3p would not require fuses.

 

[kinghappy]

Thank you everyone for the education on this, kept me from making a mistake. Will probably start with 2s2p and then hookup 2 more shortly after. Wish It had 2 mppt inputs, doing an east west install and would be great to see the differences between orientations in my particular install. I would normally think west would produce better but in S. Fl. we get a lot of afternoon storms in the summer. So maybe east for the 3rd string would be best.

 

[Rednecktek]

One of the nice things about solar is that you can have multiple charging systems on the same bank, so if you had a east facing string talking to a controller, you can have a west facing string on another controller all connected to the same batteries. The two controllers will ignore each other and just try to do the best they can independent of each other.

 

[kinghappy]

so get a stand alone charge controller for one bank to gather data?