Solar System for a Catamaran

Solar System for a Catamaran

When planning a solar installation on a catamaran you first need to consider shading.  If all the panels are shaded equally then you can group them together with a single charge controller.  If however you end up with panels that are Port, Starboard and Aft and would have three different shading characteristics then you would end up with three charge controllers.

Next you need to see how many watts of solar you will have per charge controller by referring to the table below.  This table is for a 12 volt battery system.

Finally you need to decide if you will put the panels in series or parallel, and what the open circuit voltage will be when you do that.  

Putting panels in series raises the voltage and gives the charge controller more to work with.  It also means that you can have smaller wires between the panels and the controller because with the higher voltage the current will be less. Panels in series (when blocking diodes are fitted) are more tolerant of partial shade.  So there are some advantages to putting the panels in series to get a higher voltage.  However there are  limits to how high you can afford to let the voltage go.  

The first limit is that of the charge controller.  In the table above the first number of the charge controller at the top of the list (75/15) refers to the maximum allowed voltage.  For this example 75 volts is the maximum open circuit voltage allowed.  Victron ask you to please keep it 10% less than the max if possible.  

The second limit is to do with how electricity and water don't mix.  If you get the voltage too high you could get an electric shock and so for that reason you might want to keep it no more than around 50 volts.  There are no standards for this at the moment so you just have to use common sense. When using higher voltages its always a good idea to get the Wirebox terminal covers for the MPPT's to ensure nobody gets a shock.

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