Solar sailboat

[SomedayBlue]

Hi solar power folks,

I'm in the process of adding solar power to my sailboat. In my quest for info, I found Will's youtube channel, which has been a useful source of information.

My set-up: almost 2 years ago I bought a sailboat with a 48v Electric Yacht motor. The motor will re-charge its battery bank at a fairly low rate: on the order of 100w when the boat is sailing ~6 knots. My boat also came with a 2kw Honda generator in a deck box, but no solar. In addition to the 48v 12,000wh motor bank, there is a 200ah 12v house bank. Both banks use 6v AGM batteries and are mostly getting recharged at the dock.

There are several issues with the Honda generator, but the biggest is one I realized after I got CO detectors for the boat: it produces a lot of CO. For this reason, IMO, it is unsafe to run while at anchor. It's also very noisy and uses gas. I want to cross oceans and sail to remote places, so a big part of the attraction of solar is that it cuts down on the consumables I will need.

My current project is adding the solar power components to the existing system so I can recharge away from the dock without running the generator. I've bought all the components I think I will need for the electrical connections and hope to install them all soon. I've attached two diagrams, one with just the existing components and one with the stuff I plan to add.

 

[snoobler]

sounds like you intend to get some kind of MPP Solar or Growatt all in one unit. I would discourage this. You want reliability. Victron is extremely popular with the seafaring folk.



A Victron Quattro 4kW/48V (I have two of these - love 'em) with its dual AC input (grid and genny) would pass everything through. It would also replace the existing 120VAC/48VDC charger.

You would lose about 12% efficiency on the 12V charging, but you've simplified the system, and expanded its capability. You could also just forego the 12V system entirely with the 48V-12V transformer, though it wouldn't hurt to keep it as backup being floated all the time with the 120VAC/12VDC charger (might use about 10-20W). Since it's AGM, you can just charge it once a month as AGM rarely lose more than 5%/month sitting.

The issue with solar is shading. On a sailboat, you have massive potential for shading. It destroys panel output. I would pack as much solar on there as you can using the largest panels you can as well as lightweight ETFE flexible panels you can throw around wherever you like and deploy as needed for supplemental power.

 

[SomedayBlue]

Hi Snoobler,

I do like simplicity and reliability, but I also like redundancy which sometimes conflicts with simplicity. If you look at the 2nd diagram, you will see that I do plan to add a 48v to 12v transformer but also keep the 12v battery bank, for now. I consider the 12v system super critical as it runs the navigation lights, all the electronics, and the bilge pumps. Being able to run the 12v system off either battery bank seems like an important redundancy to me. Also, I'm adding a 100w 12v solar panel and a 12v 10a PMW solar charge controller to the 12v side.

I am aware that Victron products have great reviews. One thing I did not include on the second figure is the Victron BMV-712 I will be adding to monitor the batteries so I can get a better picture of how my system is working. This is my first attempt with solar, and I want to get good data so I will know if it is working the way I need. However, they are also very expensive. I bought the Growatt 3kW/48V unit because I can afford it now. The Victron Quattro does not include a MPPT charge controller, so one would need two Victron boxes, which together cost about 4x what The Growatt or MPP Solar boxes do. The Growatt will not fit in the location of my existing 120v to 48v charger, so I do plan to leave it wired up in case the Growatt proves unreliable.

As far as the 2 AC inputs goes, if I decide to keep a generator on board, I will probably replace the gas-powered Honda with a marine diesel one, mostly due to the CO issue.

I hope to add more solar panels in the future. However, space is at a premium. I was initially thinking of using 300w panels, until I took some measurements. To start with, I'm installing two 200W 24v panels for the 48v system. After I figure out how to attach those to my boat, I'll see if I can find places to attach more. Places that they won't get in the way and won't be shaded are very limited.

This solar install includes a lot of me trying things out. I do appreciate your suggestions, and even if I don't incorporate them now, I may when I revise the system!