Two panel, one charge controller aboard sailboat..Questions???

11 Posts
Mar 29, 2009 01:55 pm
Two panel, one charge controller aboard sailboat..Questions???

I live aboard a sailboat, it is on a mooring, it swings 360 degrees around the mooring twice daily with the tides. My masts, 65' and 40' above deck (it's a katch rig) aloft and cast shadows over all of the decks thus shadows appear over the pv panel several times within an hour. Because placement of two panels (I currently employ one 130 watt KC panel)(I want to add another panel) and will each have different shadows at the same time, or one may have no shadow, the other with a shadow, I didn't plan on a combiner, or any type of isolation between the two panels,  both directly wired to the mppt. Question: If one can understand my situation here, how should I wire to the charger? How would you do it given the unusual sunlight exposures unevenly?
220 Posts
Mar 29, 2009 10:57 pm
Re: Two panel, one charge controller aboard sailboat..Questions???

 hello stephen.

 ahh, life aboard. can you tell us more about your charge controller model # and the proposed placement of your second module? ie: distance from first module and from your controller? we may indeed want some kind of isolation here.
11 Posts
Mar 30, 2009 07:25 am
Re: Two panel, one charge controller aboard sailboat..Questions???

Hi David

My charge controller is a Blue Sky 3024i. Placement for the existing panel is on the fwd. cabin top, approximately 21' in wire cable distance (12awg) to the mppt. I am planning to install a second  pv panel attached to the stern rail, also approximately 21' in wire cable length from the mppt. I was thinking I could connect both cables together at the mppt.
220 Posts
Mar 30, 2009 04:27 pm
Re: Two panel, one charge controller aboard sailboat..Questions???

 well..stephen this is just one guys opinion and hopefully we might get a few more for what they are worth. we can spent days weighing our options, crunching the numbers, and graphing the financials of our decision but in the end it all comes down to compromises. i think we both know that this is not the ideal setup we are proposing here.

 the ideal setup might be to have both modules in the same location and strung in series as a 24 volt array. or to run them on separate controllers with the modules fore and aft.

 but i believe in the end what you want to do will work and work fairly well. and considering the full time losses incurred trying to provide isolation of the modules from each other i would just let the kc130's bypass diodes do their job and let the controller sort out the rest.

 we would be doing a disservice to other forum readers if we did not mention the needed overcurrent protection for this setup and just for the convenience factor you can't beat a manual breaker of the proper rating. i might go with a 15amp breaker for each of the 12awg positive kc130 strings right near the controller then from the breakers to a combiner block then the short run with 4awg out to the controller input. the same with the 12awg negative but without the breakers. from the controller we might go with the same 4awg and a 25amp breaker then on to our battery bank. yep, a little overkill here with the 4awg and little underkill with the 25amp breaker. that's just me being over cautious. along those same lines we might consider trading that 12awg in for a 6awg or 8awg for the pv runs.(for voltage drop reasons not safety concerns).

best of luck to you...

...perhaps a few other folks might chime in to add their two cents worth.

kind regards, dave

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