Ready to install solar panels on a boat, what should I know？
Posted by Fresh-Revolution-895@reddit | sailing | View on Reddit | 17 comments
I’m planning to add some solar panels to my boat, mainly to keep the batteries charged and power a few small devices during trips that last a few days. Honestly, I don’t know much about installing solar on a boat. I’m not sure how much power I’d actually need or what kind of mounting setup would be both secure and space-efficient.
I came across the Renogy Shadowflux panels, which are said to perform well under partial shading. That really caught my interest since the sails and rigging often cast shadows on the deck. Do you have any advice or tips I should keep in mind?
umo87@reddit
we have 3x205w solar panels and 3x 105amper gel batteries mmpt and 2000w invertor. 2 12v fridges, all boat electronics, 2 laptops and a internet modem works perfectly for 24 hours even on a partially shady day.
RedDgc@reddit
I have two 100 watt flexible panels wired in parallel mounted on top of dodger on my 30 ft sailboat. They are connected to a Victron 75/15 mppt controller with Bluetooth. On a sailboat parallel connection may work better due to shading caused by sail and boom, while sailing or at the dock. The panel's primary function is to charge batteries that are in turn running fridge (24 hrs) and Garmin instruments, stereo, VHF, etc, while sailing. Or fridge and cabin stuff when at anchor. I also have a Victron BMV-712 Bluetooth battery monitor. This has its own wireless network to connect with the mppt controller.
wkavinsky@reddit
You need an MPPT controller.
The panels connect into the MPPT, the MPPT to the batteries.
Configure the MPPT with the right chemistry and voltages for your battery, and make sure it's sized correctly - the voltage on the MPPT refers to the incoming panel voltage it can handle, the amperage refers to the power that it can deliver to your batteries.
As an example, the Victron 100/50 can handle a maximum of 100v in, and 50a out to the batteries - for a 400w panel, that's two panels in series connected in (you can add more panels in parallel), and (for 12v) a maximum of 600w out (1200w for 24v, etc, etc).
As usually recommended, Victron make very good controllers, but they are on the higher price side - then again, they also aren't likely to fry your batteries, or start a fire, so you get what you pay for.
Panels will list in their tech specs an "open circuit voltage" - this is the max input voltage to your MPPT.
bright_yellow_vest@reddit
I’m pleased with my battery tender brand MPPT charge controller, if anyone is looking for a more affordable option
https://www.batterytender.com/products/battery-tender®-30-amp-12v-24v-mppt-solar-panel-controller?srsltid=AfmBOooxGDQpi5uvTNyztAo5QbmJUi-8EHW65iHyULrHnIgx-X70zWVT
0not@reddit
That's more expensive than a similar Victron MPPT controller. What am I missing?
bright_yellow_vest@reddit
Apparently so. I must’ve seen a $400 Victron and looked no further
RedDgc@reddit
Yeah, and the link doesn't work either.
-Mitchbay@reddit
This is the right direction. Also know that panel efficiency can also be thought of as power production per unit area. So, the more efficiency the panel, the more power it can produce in a smaller area. This tends to be important on a boat. Rigid panels are going to have better efficiency and solar production than flexible panels. If you can manage, go rigid.
gsasquatch@reddit
My devices add to about 34watts so I bought a flexible 50 watt panel and an el cheapo controller. Then put 2+2 together.
50 watts will get me more volts at the end of 24hours sailing than I started with if it is sunny. Or, the battery lasts a couple days on its own, so, I really only need so much add.
Biggest challenge for me was where. Which is why I went flexible, like a rigid panel is a 20lb beast with glass and al an inch thick my flexi panel is like 2lbs and 1/8" thick. Makes mounting a lot easier, anywhere you can put a piece of 1/8" ply of the same size.
I put mine on the cabin top for cruising but put it below for racing where people will cross on tacks, so I have some para cord tied to it that I can lash it down to random deck hardware when I want or take it off when I don't want. Vang partially shades it, but that hasn't been a big problem, it still adds volts.
I'd permanently mount it, but there's no where on my boat someone isn't stepping. Maybe a deal off the stern rail, that seems common with folks. Forward hatch might be nice, but I couldn't find a panel the same size as my hatch, and panels smaller than my hatch were only like 20watts.
Panel was less than $100, so I figured if it crapped out, it wasn't an expensive lesson, but it's been chooching for 4 years now. PWM controller was $30. So less than $150 all in, and it's done fine. YMMV
Here's how I calcuate my power
VHF is .6 amp listening x 12v is 7.2watt x 24 hours is 173 watt hours
Auto is 1.5a nautical, 18 watt x 8 hours (about 1/3 the time) is 144 wh
LED I guess about 1 watt per, red, green, white = 3. Or anchor is 1 plus a couple interior, either way is 3 x 8 hours, is 24 wh
Phone charger is 5 watts, and that is either phone or my navigation tablet. x 24 is 120 watt hours
All that is about 34watts, or 461 watt hours. So, my 50 watt panel has to get 9 hours of sun. Except, my battery is 1200 watt hours and can run everything on it's own for a couple days. So if the panel only does half of what it needs two, like 200 watt hours, then I've got 4 days, and that's enough for me.
In practice, the panel has been more than enough, and after a couple days trip I've ended with a higher voltage than I've started.
HoldAccurate3880@reddit
Sunenergy, Recsun, Huasun, Jinsun ZNshins and GSHK all have 600 watt-700watt 2384mmx1303mm panels. Also there has been a paradigm shift breakthrough. China (Longi Research )and Germany ( Fraunhofer Institute) 34-36% efficiency has been achieved and verified. the next generation of solar panels should hit the market some time in late 2026, ESTAMATED AT 1100+ watts for a 7.8'x4.2 panel.
ArtVandelayII@reddit
Take a look at CIGS panels. There are some good reviews on YouTube of BougeRV’s 200W flexible CIGS. They are extremely shade tolerant, and unlike traditional flexible panels, they’re very durable.
You could mount those on a bimini without needing to install an arch.
jibstay77@reddit
I just watched an Expedition Evans video and he drilled a 3 inch whole through a BougeRV panel and the darn thing still worked. Pretty impressive!
youngrichyoung@reddit
Jim Baldwin of Atom Voyages has a very detailed write-up on a small 2-panel setup for modestly sized sailboats. https://atomvoyages.com/the-atom-solar-tracker/ I have built this project and it worked great, though some of the steps required skills or tools I didn't have and had to hire out.
If that seems overkill, you just need a small panel and an inexpensive controller. I had an 18' trailer sailer on a mooring with a trolling motor for a while, and we found something smaller than this was adequate: https://www.amazon.com/SOLPERK-Maintainer-Waterproof-Controller-Adjustable/dp/B08GX19KT9/ref=mp_s_a_1_3_maf_2
If the Atom Voyages plan seems inadequate for your needs, you are getting into arch and multi-panel territory. But it doesn't sound like that's what you need.
george_graves@reddit
Don't even bother with a PWM controller. They shouldn't even sell them. But even Victron does. It's not one of those things where you get 90% of the performance for 10% of the cost. It's more like 50% the cost for 10% the performance. It's really bad.
revelm@reddit
they go on the top, not the bottom
NB-DanTE@reddit
I'd say figure out your average daily power use first. This will help you size the system better, or you may end up upgrading later.
widgeamedoo@reddit
What sort of boat? How big is the boat? Does it have an engine? Where are you thinking of mounting the panels? What exactly are you thinking of running off the power you generate? Lights? radio? charging phones? refrigerator? instruments? Navigation systems? Is there anything there already?