A Guide - Choosing and Wiring Your Boat's Solar System

[follyrob]

Hello Cruisers!

I have been a long time reader of cruisersforum, getting little bits of information over the years but never making any posts of my own. I thought it was about time that I gave something back and got a little more involved in the community.

I recently purchased my own boat and am setting off across the Pacific Ocean. When I purchased the boat it had no cruising gear whatsoever and I had to install all my own systems. I learned a whole lot, and I thought I'd share some of that knowledge.

I wrote a guide on how to choose and install a solar pv system on your boat and would like to share it with the community. I hope it can be of use to many of you. It can be viewed on my blog below:

Guide to choosing a solar system for your cruising yacht

Guide to wiring the solar system on your cruising yacht

I hope everyone enjoys the info. I plan to keep the blog quite updated on my way across the Pacific as well, writing about my experiences and some how-to articles so if you like the look of it then bookmark it or sign up to be a follower.

Thanks for all the info over the years cruisers!

[Dreaming Yachtsman]

Rob,

A fellow cruiser recently asked me how to size a solar panel array for his boat so I was delighted to see your "guide". Unfortunatley, you mistakenly interchange amps with amp-hours in several places throughout the text and in the tables. Until that discrepancy is corrected, I can't send him the link - he is a mechanical engineer and might get confused by the improper terms.

[mrm]

I'll second the need for clarification of units in table. Also, proofing the math might be in order. For example your guide states:
Marine VHF: Amperage(0.2), Hours of expected use(24), Daily Usage(0.48).
Obviously, daily usage should be 4.8 Ah (Ampere hours).

Good idea, though.

[follyrob]

Nice one guys, you are both exactly right, I'll make those corrections right away.

[sailinglegend]

Originally Posted by follyrob

Nice one guys, you are both exactly right, I'll make those corrections right away.

Another correction about MPPT controllers.

Most CAN accept a higher voltage so you can wire 4 panels in series and send 48 volts plus down to the controller and not fry it. The great advantage with this set up is that the cables from the panels to the controller don't need to be so large. Higher voltage = lower current. You've said nothing about the importance of the correct size cables so that that all those expensive amps - or is it Ah - aren't lost on the way?

Sorry, but there is a lot of missing and incorrect info in your article!

[Paul L]

100 = 17.5 x Amps

Amps = 100/17.5
Amps = 5.7

So in solving that formula, I just found that a 100 watt panel can produce 5.7 amps an hour at maximum capacity, since panels are rated at their maximum output capacity. Now you may think, "GREAT! my 100 watt panel will put out 5.7 amps for 12 hours of sunlight a day."

Your calculation for power doesn't make sense. What you care about is how many amp-hours you can replace into the battery. So at 17v you have 5.7amps. But you won't be putting 17v into your battery. The charge controller will be putting in something like 13v. The net power will stay the same, 100watts. So at 13v a 100 watts is 7.7amps. Less conversion losses that is what will enter your battery, not the 5.7 you have stated.

[jm21]

A good guide to sizing a solar system would be great though...looking forward to the completed product. Good luck. I've been reading a ton of posts on here and would be nice to see all the great information available here organized a bit. Amazing how much more affordable solar is recently...totally changes my ideas about power consumption while cruising.