acidbraker avatar image
acidbraker asked

Small solar solution for Marine use

Hi there, first post...I'm brand new to the solar game and trying to get my head around it. My plan was to use a LiTime mini lifepo4 12v 100ah battery to power all the accessories on my smallish fishing boat. I just purchased a Victron smart solar 75/10, and planned to use a small flexible Voltset 30W panel to charge/maintain the battery through the mppt. I'm new, so I think I messed up and will be unable to use that small of a panel. My question is, what can I use? I'm trying to run as small and light as possible. I plan on just placing the panel up on top of the cloth bimini top. Thanks for any advice.

smart solar set-up helpsolar sizingmarine mfd app
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3 Answers
dc-marine avatar image
dc-marine answered ·

Your 30w panel will work to maintain the battery and slowly charge it, but may not be sufficient if you go out several times a week. You may want to look into a 100w panel instead.

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acidbraker avatar image
acidbraker answered ·

I was looking at the specs for the Victron 75/10 - I was kinda thinking that the 30W panel might not have enough oomph to make the +5 volts to push the MPPT into charging mode. It also says that it recommends a minimum of 36 cells. The Sun power 100W flexible panel only has 32 cells if I'm counting right. What am I missing?

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dc-marine avatar image dc-marine commented ·
Check the operating voltage rating of the panel. It must be 17vdc or higher. You can also connect two panels in series to increase the voltage and allow charging when shaded.
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kevgermany avatar image kevgermany ♦♦ commented ·
Avoid flexible panels, they can have a very short service life. Friend of mine has had to replace his after 2 years, and it's not unusual.

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madmaxx avatar image
madmaxx answered ·

I am not expert and asked my first question here today. Nevertheless I allow myself to tell you the following:
You are lacking a strategy!

1. Consumption
You either know or have to find out about the power consumption of your electrical devices. If everything is in 12V, you can roughly simplify your calculus by using amp hours (Ah) instead of (Wh).

2. Means of battery charging
Wil you apply solar charging only or do you have access to connect a charger when being in a harbour?
If yes, how many days does your battery has to last?

3. My experiences with a module labeled "25W"
I have a solar panel in my car which is supposed to generate 25W. Stuck behind my windscreen it just generates around around 200-300 mA during sunny hours in May in Mid-Europe which barely manages to counter self-discharge of my battery, counter the current needed for the integrated analog clock in the car, leak current from my amplifier and compensate for 9 mA use of the solar charger itself.
Now you see why you should find out about your consumption! :)

4. Be quantitative
"smallish fishing boat" could be a small trawler or a boat like the one in the film "The godfather".
What is needed is your knowledge about disposable space for solar modules instead...

"small and light as possible" suggests using LiIo-batteries instead of LiFePO4. That will matter if you have to carry the battery. "small" contradicts your possible unknown consumption needs.

Good luck!

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acidbraker avatar image acidbraker commented ·
1: I don't really know. Everything is 12v - it will be powering the bilge pump if it rains, the 7" sonar, the livewell pump, the dash gauges, and a USB outlet for keeping the cell phone full.

2: Only solar charging once out on the water. Primary use is for boat camping/fishing for 4 days. Boat is only used about half the time during daylight hours.

4: Boat is a Alumacraft Trophy 185. The only space I can really use while the boat is in use is up on top of the bimini top. I'm planning for LiTime lifepo4 batteries. They will remain in the boat. I'm trying to lighten the load by going with lithium because I always have a ton of stuff in the boat when I'm taking the kids out. Getting rid of the lead-acid batteries just frees up a little more carrying capacity for coolers and fishing gear.

I'll try to be better about getting specifics on usage. I'm working on gaining knowledge. Thanks folks.

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kevgermany avatar image kevgermany ♦♦ acidbraker commented ·
Factor panel shading into your calcs.
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