3 panels and 3 MPPT controllers?

[Frankly]

Watch out for the DC rating of the panel circuit breakers. Some of the Carling breakers (relabeled by most everybody) are only rated at 32 VDC. Supposed to break both legs on an ungrounded circuit (solar panel) but most don't and some depend on throwing bedsheets to stop current flow.

I used a small Blue Sea Ammeter and shunt on the output feed to see how charging is going.


Frankly

[mvweebles]

Question: I have room for 4x200W panels on my hard-top. No shading problems, but due to camber on hard top, the two pairs will be out-of plane by about 10-15 degrees. To compensate, my "Dudes" recommended separating into two strings (Port and Starboard) into a string-combiner arrangement as shown in attached diagram. Does this reduce the effect of out-of-plane panels?

BTW - the panel builder (great guy in the great boating state of New Hampshire) caught the challenge of finding a breaker of >32vdc. Took him a while to find the right one - BSS makes one, but not in all of their switch form factors.

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[markcouz]

You would be better off with 2x 30amp charge controllers (one for each string).

[Frankly]

That looks like a good arrangement for independent (P &S) controllers. The disadvantaged panels will have a reduced current output (cosine effect) and the voltage of the combined pairs will revert to the lowest voltage in the current connection.


Shunt just goes in the solar charge controller(s) negative output lead before the output breaker.


Frankly

[john61ct]

Originally Posted by Pole

Thanks. I really didn't get that part - so the 75 part of a 75/15 controller refers to the INPUT voltage, and the 15 refers to the OUTPUT amperage?

Yes, and their full user manuals are available online.

There's no need for a breaker between panels and SC. Maybe a switch, but there's one in the Victron SC controlled in the app. A physical one would be used so rarely, and worst case, it's not as if the ferrules are hard to insert/remove from the SC.

[john61ct]

Originally Posted by mvweebles

No shading problems, but due to camber on hard top, the two pairs will be out-of plane by about 10-15 degrees. To compensate, my "Dudes" recommended separating into two strings (Port and Starboard) into a string-combiner arrangement

For best efficiency, again, one panel per SC is the ideal, each getting their own MPPT optimization.

Next up would be one SC per pair at the same angle.

All going to one SC comes in third.

[Yellowjacket]

First, Noelex knows …
Second, I made several mistakes in a system similar to yours…

The controller you spec'ed has an output of 220 watts. Less than one of your panels, if on a 12 volt system. If you had three, let's say an output of 660 watts.

https://www.victronenergy.com/upload...20_48V-EN-.pdf

A 150/70 has an out put max of 1,000 Watts, mor than enough, but …

If you use a single MPPT controller, your three panels will be treated as one single panel, and if the sun falling one them is not the same as on the others, you may lose efficiency as contoller tries to balance amps versus voltage for maximum output.

Also, as you look at circuit breakers, be sure you are looking at the DC rating. Beware of some sold through Amazon. There is an approved spec for DC breakers used on boats.

[mvweebles]

Originally Posted by markcouz

You would be better off with 2x 30amp charge controllers (one for each string).

100/20A is about $40/each less expensive (AMAZON here). I assume one for each pair would be fine given each panel is rated at 9.5A/9.8A (19A-19.6A/pair)?

Wish I had known to ping you guys earlier - price of the two 20A is about the same as the single 50A.

[john61ct]

Originally Posted by mvweebles

I assume one for each pair would be fine given each panel is rated at 9.5A/9.8A (19A-19.6A/pair)?

Divide 1 panel max Watts, by your lowest SC **output** charging Volts to get the Amps per panel.

You need a SC rated for higher than that.

What Voc rating?

[Dsanduril]

@MVWeebles,

your drawing shows 56A on the charging side, that means 28A per pair (if the drawing is correct) - a 20A controller per pair will limit you a bit. Controller amp ratings are on the battery side, voltage ratings are on the solar side (simplification for the most common buck MPPT controllers).

Also, does your 1AWG wire have another fuse/breaker near the battery? The 60A breaker doesn't do you a lot of good except as a disconnect if it is far from the battery. The battery will be the source of excess current, so the overcurrent protection device should be close to the battery (7"/175mm is the ABYC standard).

[mvweebles]

Originally Posted by john61ct

Divide 1 panel max Watts, by your lowest SC **output** charging Volts to get the Amps per panel.

You need a SC rated for higher than that.

What Voc rating?

Here you go (and many thanks to to OP for letting me 'barge' a bit).

Power: 200 Watt
5 Busbar
Monocrystaline
Vmp: 21.052V
Voc: 24.335V
Imp: 9.5A
Isc: 9.87A
Maximum System Voltage: 600V
Module Efficiency: 17.0%

[Dsanduril]

In theory each panel can contribute ~15A (200W/13V) into the battery charging side of things. That means each pair can provide up to 30A @ nameplate ratings. You'll almost never reach nameplate but personally I prefer to have controllers that can get there, or close. Again, my opinion, I probably wouldn't go less than a 25A controller, and would prefer a 30.

For the voltage side of things, the math says you need a minimum of a 50V rated controller (2 x 24.335). I prefer to have some headroom, if you ever sail where the temperature is less than 25C you can get Voc above the rated value, especially in the morning. A 60V or higher rating would be fine.

[john61ct]

Originally Posted by mvweebles

Here you go
…
Power: 200 Watt

…

Maximum System Voltage: 600V

So yes each panel can be serviced by a 75/15 SmartSolar (200W ÷ 13V = ~15A)

You could pair them up in series, but then any difference between the two (partial shade transients, bit of bird poop) will impact the total output from both.

Might cost a bit more, space, wiring etc, so up to you.

If you want to parallel pairs, then go to 100/30.

[john61ct]

And for others coming along, you'll get a bit mor efficiency out of Victron's MPPT by pairing with a higher-voltage panel, say 40+ Voc

Unlike the Amps output rating where you can go quite a bit higher, increasing average but sacrificing peak output

With the Voltage side you want to stay well below that 75 or 100 etc, as IMO say 10-15%.

[mvweebles]

Thank you all for your input. I learned a lot today - amazing resource.