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I am looking at the victron range of MPPT charge controllers and would welcome recommendations on which solar charge controller to use with an array of 20x 550kw panels on a 56ft catamaran...
Boats mostly install panels in parallel to mitigate power reduction when panels are shaded by the boom or sails.
Thank you for your feedback.
That's a lot of panel for a boat. You give no data at all, so little we can offer. Have a look at this calculator.. https://mppt.victronenergy.com/#
You'll likely need multiple mppts, so you may need to decide on 'sections' to divide the total into. And a 48V battery will reduce the mppt quantity (in Amp terms).
The main things to keep in mind are that series strings raise pv Voltage, and parallel strings raise pv Current. And there's a limit on both parameters with every mppt.
Also try to keep the series V up to allow for it's reduction in poor light. I like to see Vmp for the strings at least twice that of the nominal battery V.
Have a play with the calculator and come back with your findings and questions..
The boat ( Laggon 56 ) uses 24V for its house bank and equipment, the house bank will be extended to 40kWh.
The panels are 550w ( 50V / 11A )
To use 250V DC strings was my first approach as this installation I have done already at my home, however I have been dis-couraged from high voltage strings on grounds of safety and mitigating powerloss from shading. Therefore, I am considering to bring a positive / negative cable for each panel into the technical room, fuse the positive cable, and parallel them at or near the mppt charger controller.
The question remains how many mppt solar charge controllers (MCC), obviously the higher amperage of the MCC the fewer that are needed, however I have seen the datasheet for the MPPT 250/100 that the Nominal PV power, 24 V is 2900W so that could be 5 panels in parallel 5 550W panels through each MCC.
However it states, Maximum PV open circuit voltage
But I'm uncertain as to the operating voltage range, would it operating on 50V from the panel or does it get its operating voltage from the 24V battery ?
Operating voltage is from the panels. So 5*50V panels in parallel is still 50V. But in series, you're at 250V limit of the controller with the likelihood of killing it.
Watch temps. The panel voltage drops with temperature increases/rises as temps drop, so can be dangerous in winter if you are close to the limit of the controller. Victron calculator takes this into account.
Shame about the 24V batts, it means you need twice the mppt capacity.
Running 20x wire pairs is really stretching practicalities. And one could then argue you should have 20x mppts. But I'm not suggesting that.
I'd string the panels in seriesed pairs, so 10x wire pairs, and enough V to guarantee that poor light will still produce. 150/ rated mppts would suffice, maybe even a little cheaper than the 250/'s.
3x of each string into 3x 150/100 mppt's would give a nominal 3300W for each mppt. A little over spec, but in practice you'd rarely, if ever, see them clip.
The 1x remaining pair to a 150/35 mppt.
That's potentially 335A at your batts/busbars. A lot, take care with the hardware here too..
Thank you for your detailed answer, very much apprecicated.
May I get your views on the use of high voltage dc i.e. upto 5 panels strings 250V DC per string.
I understand there are two problems with an installation like this on a boat:
I don't have an issue with higher V personally. Proper solar wire and MC4 connectors have a much higher rating than 250V, but I'd make sure they're installed carefully and not subject to possible abrasion or snagging, etc.
In the washup you may be subject to govt regulations, marine or otherwise. Eg, in my country anything above 120V dc is out of diy territory on land, and marine might be different again.
Shading is really difficult to quantify. Sometimes even a rigging wire shadow across a panel could affect the whole string, then sometimes not.
Stringing for lower V is just the cost of running extra wire. Higher V may be important for budget domestic installations, cost, convenience, ac-coupling, etc. But the shorter strings in an application like yours have no real drawbacks when in production.
You could experiment. A 4S1P string into a 250/70 (say) could be changed later to 2S2P. But sometimes the panel count mightn't suit, and you're left with orphaned panels. You really need to map-it-out to see all your options. And maybe the 'sections' I mentioned earlier will have some say too?
Assuming there is the space for the cables, is the best option to have all 20 panels in parallel ? both in terms of safety ie. max 50v ( compared with 100V ) and powerloss reduction due to shading ?
The number of mppt solar charge controllers I believe would remain the same.
6x panels into each 3x 150/100 mppt's ( 6x panels in parallel 50V 66A per mppt )
2x panels into a 150/35 mppt ( 2x panels in parallel 50V 22A )
I suppose I am trying to ask is there a benefit ( from both a power loss due to shading perspective and a safety perspective ie. 50VDC compared to 100VDC ) to having all the panels in parallel If I can figure a way to fit in all the cabling.
I suggested 10x pairs because I believe it's the best option, production-wise. On my system I see Vmp halve from spec in poor light, usually for an hour for each of sunrise and sundown. I mightn't see much W, but it's better than nil. Which you may see with just single panel strings in similar conditions.
Note too that there's a difference between Voc and Vmp, and Isc and Imp. You've quoted 66A, which is likely Imp, but the 150/100 has a limit of 70A Isc, and you should check that.
Safety wise, just ensure the installation is safe, and respected. I use 120+Vdc panel strings and 230Vac on my boat, but I'm careful too..
That’s a lot of solar power for a boat. I would recommend engaging with someone who is certified for this type of install. Lots of flow on effects like battery charge/discharge rates. Also check with your insurance regarding their expectations.
As for the layout I am considering the following
