Illustrated Guide to Solar Installations on Boats

[Copacabana]

A 30v panel can charge a 12v or 24v system (battery). I have a 30v 265w panel on my boat charging my 12v system through an MPPT controller. I would be surprised if the panels were only 12v (which is 18v output normally) at that size (265w panels are normally 60 cell panels). Perhaps the OP can clarify the panel specs.

[aybabtme]

Need more info about the specs of the panels and of the controllers to be able to answer this question.

[mitiempo]

They are probably 24 volt nominal panels which would have an open circuit voltage of 39 volts approx and a loaded voltage of about 33 volts.

I have never seen a 265 watt panel that was 12 volts nominal.

[Iains boatyard]

Ok start again .....

I need a circuit diagram for my solar system.

5 x 265 w panels, 30.6 Vmp 8.66 Imp. Canadian solar.
2 x 40 amp mppt controllers max solar input 100v
24v x 800a/h battery bank

The controllers are the same so can be run in parallel.

All I need is a circuit diagram which gives me the most efficient result.

[mitiempo]

Originally Posted by Iains boatyard

Ok start again .....

I need a circuit diagram for my solar system.

5 x 265 w panels, 30.6 Vmp 8.66 Imp. Canadian solar.
2 x 40 amp mppt controllers max solar input 100v
24v x 800a/h battery bank

The controllers are the same so can be run in parallel.

All I need is a circuit diagram which gives me the most efficient result.

Where on the boat are the panels installed?

If a pair of panels are wired in series and one is shaded you will lose output from both.

Unless the paired panels are never shaded a very good case can be made for separate controllers for each panel.

[Iains boatyard]

The question is ....


Is there a circuit for 5 panels.?

30 v panel will not charge a 24 v system
5 controllers is totally impractical
Everything else is irrelevant

Is there a series parallel circuit for 5 panels?

[mitiempo]

Still want to know where the panels are located.

What is the maximum voltage the controllers will accept? If it is 100 volts you cannot wire 3 panels in series.

More information will help us help you.

[aybabtme]

I'd wire them 2 parallel and 2 series on one controller and do something with the last one. If you do a 3p and then 2p setup, your 2p series will be limiting the current from the 3p one, so you're wasting your extra panel.

Another way would be 3s on one controller and 2s on the other one. But then each string is sensible to shading, so the question of location becomes more important, and you're pretty close to the 100V limit of your controller. At 30V, you're not getting a lot of early morning/late evening performance if you put them directly all in parallel, because your 24V is about 28.8V when full, leaving very little voltage difference in lower light.

[Iains boatyard]

There is no shade issue
I have now wired 3 into one controller, 2 into the other controller see what the day brings
I have two separate circuits coming down from the panels

[mitiempo]

Originally Posted by Iains boatyard

There is no shade issue
I have now wired 3 into one controller, 2 into the other controller see what the day brings
I have two separate circuits coming down from the panels

Whatis the maximum voltage your controller can accept. If it is 100 volts 3 is 1 too many.

[Iains boatyard]

WHY ?
3 x 30 v =90v ?
Controller 100v input

[mitiempo]

Originally Posted by Iains boatyard

WHY ?
3 x 30 v =90v ?
Controller 100v input

Because the panels will at times exceed that voltage. If or when they do it is probably goodbye controller. Victron for example recommends keeping the total panel voltage lower.

Your panels are 30 volts or so under load correct? That means their open circuit voltage is much higher. When adding voltage for input into a controller I use the open circuit voltage - its safer. That would mean in your case that 2 panels are the most you can use with one controller.

Which brand of controller do you have?

[Iains boatyard]

Ok my opinion was no need to factor in open circuit volts. I take full responsibility for my work I never install for any one else. All my solar at connections I do at night.
So testing day one, 3 panels in to one controller hit 95v so right up there. 2 panels series into one controller 66v.
That night I wired the the panels same configuration into a bus bar feeding both the controllers in parallel to the bank.
Peak volts at midday topped 70 v and 36 amps output at about 26.5 v.
However the day was slightly overcast. I think the volts will climb higher on a clear day.
My instinct says maybe 80v and hopefully 40 amps but it is all subjective considering sun and and state of charge.
Monitor again today but slightly over cast again. Thinking this will be the best combination for my situation without building a sun tracking frame. One more lockdown project done.
Unown brand of controller came with the panel kit ML 2440 MPPT solar charge controller.
User adjustable ?

[aybabtme]

When your battery is full and your MPPT stops accepting current, you'll get open-circuit voltage on the charger ports, which is going to be more than it's rated for, risking components failure, sparks and a fire.

I retract my suggestion that you put them in 3s, didn't understand that 30V wasn't the open circuit voltage.

[Iains boatyard]

Thank you but I do not agree with your supposition.
Being flooded lead acid my understanding is they will always take a trickle / maintenance charge. Plus I am full time live aboard with an inverter always on for house power, plus a fridge always on 24v so always a draw down on the bank.
I have not done research to that thinking but my understanding is the mppt charger never actually switches off.
If leaving the boat I can flick the breaker off but that then allows the bank to receive no charge which equals going flat which equals dead batteries.
Re read my last and see how I have finally wired the panels the two in series will always work against the 3 in series.
That being said in my current situation (lockdown)half the fun in the day is watching the mppt chargers looking for abnormalities and or patterns.