Winter project solar top boxes advice needed please.

[Guest]

As per title, my winter project is to convert my trusty top box into two halves by removing rear hinges (see pic) and build wooden subframes on them to mount solar panels (probably just one solar top box to begin with). The panels would obviously serve as lids. They would also be "tiltable."

They measure 1830mm x 915mm (6ft x 3ft in sensible units )

I would have the panels as near as possible to the battery bank (330ah bank)

As solar is new to my boat, I want to get it right first go so would wish to fit a controller that would allow future expansion.

Is my idea feasible, any recommendations for panel make, and sizes that would accommodate existing 1830 x 915 (6x3) boxes?

I could of course trawl through manufacturer’s data, but there is no substitute for experience, hence my questions.

Many thanks.

Edited August 21, 2015 by Guest

[emlclcy]

as far as I know the panels that measure 993 x 1650 are all 24volt

[Guest]

as far as I know the panels that measure 993 x 1650 are all 24volt

Thanks. That being the case, I would consider multiple panes on each box. I assume 12V versions can just be paralleled?

Alternatively is there a controller that will reduce 24 to 12V? Would this be too inefficient? Cheers.

Edited August 21, 2015 by Guest

[bottle]

Step back, panel voltage is a minor thing here it is the controller that controls the charge voltage.

 

For instance my panels (nominal 12v panels) actually give 19.2v they are wired in series, parallel (4 panels) giving 38.4v into the controller (MPPT) which in my case puts out up to 28.8v, (charge voltage) mine is a 24v system.

 

So as long as the controller can take 24v actually probably in the region of 29v per panel, then the controller will bring it down to the correct charge voltage.

 

 

Note: check specification of panels and get a controller that is suitable.

[Guest]

Step back, panel voltage is a minor thing here it is the controller that controls the charge voltage.

 

For instance my panels (nominal 12v panels) actually give 19.2v they are wired in series, parallel (4 panels) giving 38.4v into the controller (MPPT) which in my case puts out up to 28.8v, (charge voltage) mine is a 24v system.

 

So as long as the controller can take 24v actually probably in the region of 29v per panel, then the controller will bring it down to the correct charge voltage.

 

 

Note: check specification of panels and get a controller that is suitable.

Got it, thanks for your explanation

[BEngo]

Allow yourself some headroom in the controller max allowable input voltage as the panel output voltage is specified at 25 C and the panel voltage rises as the temperature drops. So on a bright cold sunny winter morning you could see quite a bit more than the nominal 17-19 V per panel.

 

N

[sjc]

Anyone attempting a DIY solar project could do a lot worse than download the MMPT controller excel spreadsheet below :-

 

http://www.victronenergy.com/support-and-downloads/software#mppt-calculator-excel-sheet

 

You can use it for generic products, not just those of the stated manufacturer - provided similar panels are used, note datasheet difference if necessary !

It deals with cable sizes and lengths, temperature ranges, MPPT output, etc etc - hours of fun !

Edited August 21, 2015 by sjc

[Guest]

Anyone attempting a DIY solar project could do a lot worse than download the MMPT controller excel spreadsheet below :-

 

http://www.victronenergy.com/support-and-downloads/software#mppt-calculator-excel-sheet

 

You can use it for generic products, not just those of the stated manufacturer - provided similar panels are used, note datasheet difference if necessary !

It deals with cable sizes and lengths, temperature ranges, MPPT output, etc etc - hours of fun !

Great stuff, exactly the sort of thing I need

[GoodGurl]

these are mine on top of boxs.they are hinged both sides so they can be manually tilted, they also have vents in the sides for air circulation.

[Guest]

these are mine on top of boxs.they are hinged both sides so they can be manually tilted, they also have vents in the sides for air circulation.

Thanks that is similar to what i have in mind (though won't need as many as yourself.) Vents are a good idea hadn't thoguht of that.

[Guest]

Thanks folks. for input.

These caught my eye

Seem like a good deal?

 

http://www.bestecoshop.com/200w-solar-panel-kit-with-adjustable-frame-20-amp-controller-5m-extension-cables-branch-connectors.html

Edited August 22, 2015 by Guest

[Chewbacka]

The higher the voltage the more chance you have of getting something on a dull day, but this does require an MPPT controller.

My set up is for 24v, and my two panels in series will give about 70v on a bright day. Higher panel voltage for a given power output does reduce the system losses a bit.

[Peter-Bullfinch]

Catweasel, does the set up you are looking at have an mppt controller? Have a look at Bimble perhaps.

[trackman]

Look at Bimble Solar's website. Get an MPPT controller, that will sort the voltage to suit your batteries automatically. A PWM controller will also, but it will give you less power from the same panels.

We have 3 x 68W panels and they run our lights, fridge, radio and phone chargers all summer for free. In winter we get only a fraction of the power though, and have to run the engine for battery charging when we're aboard.

Even in winter the solar keeps the batteries fully topped up when we are off the boat and all is shut down.

[Guest]

Thanks people for input. Will look at Bimble as suggested and MPPT.

Trackman your pattern of use is identical to ours so that is very useful