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wouldrathersail 03-23-2012 03:08 AM

Yet another Solar installation thread - comments/advice requested on install specs.
Hello folks,

I've been lurking and reading for a bit now, seems like there are some very knowledgeable folks here, so I'd like to run some install specs and see if anyone has any comments. I also have a few questions regarding wiring runs.

This is actually an install on a 43' trawler style boat, we're both sailors, but liveaboard full time so for space we're on a powerboat. We're planning to do some extended anchoring this summer, and we do not want to run our generator unless we absolutely have to.

Our electric budget we way way overestimated at about 215 ah/day, just replaced our house batteries with 6-6v wired as 12v lifeline GPL-4CT for a 660 ah bank. We're getting ready to install 4 sharp 230 watt 24v. solar panels with a MorningStar TriStar MPPT 60 charge controller. We're going to set up a series/parallel install to get 48v. to the controller.

Mr. Ohm and I have a passing aquaintence, and running the numbers it looks like this config should work so we could run for a few days if we have cloudy weather, yet still be able to keep the batteries topped off most of the time. Hopefully, cuz the stuff arrived yesterday :)

On to the wiring questions...I have the ideal location for the controller, but I don't think I can get the wiring to work to place it there.
When combining the panels, here are the amp specs..
Short Circuit Current (Isc): 8.48 Amps
Maximum Power Current (Ipm): 7..67 Amps
Series Fuse Rating: 15 Amps

So if I'm understanding Mr. Ohm correctly, I should be budgeting for (on the generous side) 20 amps.
The panels utilize MC4 connectors, and the largest wire I can find is #10, which would mean that the longest run I could do from the panels to the controller with a 2-3% voltage drop would be 30 feet (one way)? Does this seem correct?

Thanks in advance for any input y'all could provide.

mitiempo 03-23-2012 02:23 PM

Re: Yet another Solar installation thread - comments/advice requested on install spec
10 awg is pretty small for a long run. I would go heavier. You want the highest voltage you can get at the controller. I would use 8 awg at a minimum.

From the controller to the batteries is even more critical - you want the voltage at the controller to have as close to zero drop at the batteries as possible. The controller should use heavier wires to the batteries and be as close to them as possible without being in the same compartment - aim for 2 or 3 ft and use 6 awg or 4 awg to minimize loss.

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