Solar configuration

[kje]

Let's assume I have 40 panels 250w Isc 8.9a Voc 37.8
What is the best panel configuration for the MPP MAX 11KW? It has max 18a pv input current...


sunshine_eggo wrote on diysolarforum: Current limit is more flexible. Going a little bit over the current limit is typically fine as the unit just wont pull more than its max.
https://diysolarforum.com/threads/how-to-wire-and-how-close-to-amp-limit-help-please.39840/

With that in mind could this work?
10s2p for 1 string 378v @ 17.8a
10s2p for 2 string 378v @ 17.8a

The 486 is way too close as over-voltage from low temperature voltage increase can kill the MPPT. 7S is likely better. Depending on your panels, they should be good on voltage down to about -20°C.

Current limit is more flexible. Going a little bit over the current limit is typically fine as the unit just wont pull more than its max.



Power limits are also more flexible. They tend to represent what the unit can deliver, not what it can have on its input.

I wouldn't hesitate to put 7S2P on each MPPT.

 

[sunshine_eggo]

10S2P / MPPT would be my choice. You're under Voc and PV current limits. Win.

Some models indicate a higher Isc limit elsewhere in the manual.

 

[kje]

Some models indicate a higher Isc limit elsewhere in the manual.

For the MPP MAX 11KW?

 

[sunshine_eggo]

For the MPP MAX 11KW?

I don't know for certain, but I've seen in similar units where 18A is the maximum it can utilize, but 22A is the maximum Isc you can put on the array. It doesn't matter for you because you're under the 18A limit. All is well.

 

[kje]

I have 6 230w panels with following specs:
Voc: 36.9V
Isc: 8.31A
Vmp: 30.2V
Imp: 7.62A

What is the best panel configuration for the MPP MAX 11KW?

 

[sunshine_eggo]

6S on its own MPPT

 

[kje]

6S on its own MPPT

The same with this inverter? I have a Voltronic Max 8kw. Is it possible to have 3s2p? It's often shading on three of the panels...

And what size circuit breaker? I assume I don't have to fuse the panels in 3s2p configuration?



I don't understand the manual with the recommended solar panel configuration:
What is a string? What is the difference on 6pcs in series and 6pcs in series, 2 strings?

 

[sunshine_eggo]

The same with this inverter? I have a Voltronic Max 8kw.

Yes. It's a high voltage MPPT as indicated by the max solar voltage of 500V

Is it possible to have 3s2p? It's often shading on three of the panels...

It is possible, but I wouldn't recommend it. The MPPT voltage range is 90-450V. 3S of your panels will barely be above 90V in PERFECT conditions. Your warm panels in 3S in full sun will almost always be BELOW 90V.

6S MAY function as well as 3S2P depending on the nature of the shading and the effectiveness of the MPPT. The bypass diodes in the panels should help mitigate SOME shading issues.

And what size circuit breaker? I assume I don't have to fuse the panels in 3s2p configuration?

Not needed, but if used, refer to the fuse size on the back of the panel for fuse/breaker needed.

I don't understand the manual with the recommended solar panel configuration:
What is a string? What is the difference on 6pcs in series and 6pcs in series, 2 strings?

View attachment 200787

Those are purely examples. Note the third column. That's the primary driver. If you have 4, 12, 16, etc. panels, that's the recommended or possible configurations.

Note the line above where it indicate 12 panels should be 6S on each MPPT. Same would hold true for simply having 6 panels - all 6 on on MPPT.

Note that they provide NO recommendations that results in only 3S on either MPPT. They have a minimum of 4 at all times.

Your circled bit is another way of saying 6S2P.

 

[kje]

Yes. It's a high voltage MPPT as indicated by the max solar voltage of 500V



It is possible, but I wouldn't recommend it. The MPPT voltage range is 90-450V. 3S of your panels will barely be above 90V in PERFECT conditions. Your warm panels in 3S in full sun will almost always be BELOW 90V.

6S MAY function as well as 3S2P depending on the nature of the shading and the effectiveness of the MPPT. The bypass diodes in the panels should help mitigate SOME shading issues.

Ok, thank you, then I'll go for 6S

Not needed, but if used, refer to the fuse size on the back of the panel for fuse/breaker needed.

Ok, no fuse in 6S configuration.

Anyway I want a breaker to cut the power if I want to.
What size circuit breaker do I need before the inverter?

Your circled bit is another way of saying 6S2P

Ok, so strings is the same as parallel.

 

[sunshine_eggo]

Ok, thank you, then I'll go for 6S

Ok, no fuse in 6S configuration.

No fuse for a single string or two strings in parallel.

Anyway I want a breaker to cut the power if I want to.
What size circuit breaker do I need before the inverter?

1.25X the wire rating. The "max fuse" value on the pack of the panel is always a good option too.

 

[kje]

No fuse for a single string or two strings in parallel.



1.25X the wire rating. The "max fuse" value on the pack of the panel is always a good option too.

Where is the "max fuse" value on this? Should it be listed here?

 

[sunshine_eggo]

Hmmm... I guess not everyone puts it on their label.

For a single string, 15A
For two strings in parallel to a single breaker 25A

 

[kje]

Hmmm... I guess not everyone puts it on their label.

For a single string, 15A
For two strings in parallel to a single breaker 25A

Ok, I've bought a 63A breaker, it's maybe too big?


Wiresize: is this correct?:

I have 6S 230w panels. 230x6=1380w

Vmp=30v so 1380/(30x6) = 1380/180=7.66A

So I have to use a wire that's good for 7.66A?


1.5mm2 (15awg) wire is good for 15A so it should adequate?

 

[sunshine_eggo]

That would suffice, but I would prefer to use 10 or at least 12 awg equivalent.

Make sure you don't use solid wire as that tends to make poor contact with many types of connections. Fine strand wire is typically preferred. Whatever the case, best to match the connector type and wire type.

 

[kje]

That would suffice, but I would prefer to use 10 or at least 12 awg equivalent.

Make sure you don't use solid wire as that tends to make poor contact with many types of connections. Fine strand wire is typically preferred. Whatever the case, best to match the connector type and wire type.

Ok nice. I've already a 2.5mm (13awg) wire buried from the garage to the battery shed.

What about my 63A circuit breaker, is it pointless to use?

 

[sunshine_eggo]

Ok nice. I've already a 2.5mm (13awg) wire buried from the garage to the battery shed.

What about my 63A circuit breaker, is it pointless to use?

No harm in using it as a on/off switch if it can handle the DC voltage and current.

 

[kje]

No harm in using it as a on/off switch if it can handle the DC voltage and current.

Ok. But according to your "1.25X the wire rating" statement I should have a 25A breaker when using a 13awg wire which is good for 20A? This is for protecting the wire?

 

[sunshine_eggo]

1.25X is the answer when you must have over-current protection. It's easy to just throw it out there, and it's a good rule any time you're selecting something for ratings, i.e., if you needed to dissipate 8W of power in a resistor, you would get a resistor rated for 1.25 * 8W = 10W.

The reason that single strings and two parallel strings don't need fusing is that the panels themselves would self-fuse, i.e., something in them would fail going open circuit. This value is usually on the sticker or the datasheet. I'm still a little shocked it's on neither for your panel.

When fusing isn't required, amperage doesn't matter provided the switch or breaker or whatever can handle at least 1.25X the max current.

 

[kje]

1.25X is the answer when you must have over-current protection. It's easy to just throw it out there, and it's a good rule any time you're selecting something for ratings, i.e., if you needed to dissipate 8W of power in a resistor, you would get a resistor rated for 1.25 * 8W = 10W.

The reason that single strings and two parallel strings don't need fusing is that the panels themselves would self-fuse, i.e., something in them would fail going open circuit. This value is usually on the sticker or the datasheet. I'm still a little shocked it's on neither for your panel.

When fusing isn't required, amperage doesn't matter provided the switch or breaker or whatever can handle at least 1.25X the max current.

Thank you very much!

How to determine wire size and circuit breaker between inverter and battery?

My battery is 48V 270ah (13kwh)
Here is the inverter:

 

[sunshine_eggo]

Consult the manual and/or size for the 182.2A DC input listed.