# Solar power tied in to boat, or separate?



## acidMia (Aug 3, 2016)

Hey all, long time  love what you've done with the place  

Im trying to figure out how solar stuff works! And figured some friends here would know a thing or two about a thing or two in these regards. 

I have a 12v system onboard already, as you do with boats. It consists of three batteries; one for each engine plus a house; and a charger that is hooked up to the shore power. I'm ok with not having an inverter at this point, but I would like to add one down the road, so whatever I end up being here will need to be open to that.

I have a lot of questions as I'm in way over my head with all of this, but question 1 is: can I even tie in to this existing 12v system? or should this be left as it is, with a separate set up for the solar panels? 

The next set of questions is how to get it set up in such a way that I can start small now, but leave it open to scale down the road. I want to start with a small charging station for my phones and tables and laptop and whatnot, to see how it all works together. 

Eventually Id want to open this up to the 60A service I currently have onboard (not that I ever use even half of that power as it is now). I guess I would need to understand how to calculate how many panels I would need to achieve that, if its even possible with the limited space I have on a boat! And then I think the controller would be my limiting piece there??

As always, any and all help is greatly appreciated


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## Chiefster23 (Feb 5, 2016)

I wouldn’t tie into my engine starting batterie. First, starting batteries are not deep cycle so they are not suitable. Second, it would really suck to drain your batteries down with lights and chargers and then have desd batteries when you need to start the engines.


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## Captainrich (Jan 26, 2021)

ok, what kind of boat are we talking about?

First, you can tie in solar panels to the existing system onboard. Most panels put out DC current at 12 volts +- .
It will act like a trickle charger, replenishing the electricity in the batteries as needed. 

I would start by connecting a simple 200-300 watt panel to your house battery using alligator clips. 200 watts at 12 volts give you 8.3333 amps. So in theory, it would recharge a dead 800 amp battery in a little under 100 hours of sunlight. 
As for additional capacity, you can add a second house battery by wiring it in parallel. (+ to + and - to -). just be sure that both batteries are the same size and type. Deep cycle is best. It is best to buy them both together when you do this. 

I plan to do this to my boat this month. My plan is for 2 800 amp batteries connected to a 400 watt panel mounted to the hard top. That will give me the same charging rate as above with twice the capacity.


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## Piratesailor (Nov 9, 2012)

I have a solar on my sailboat. You surely can tie it into your existing charging system and yes, gets a good high quality controller. Start with a 180w panel and a good controller and you’ll be able to recharge you electronics and keep your batteries topped up Including your starting battery. My boat has one start battery and two 4d house batteries. All are AGM.

if you‘re using wetcell batteries I suggest you change over to AGM’s. 

I think @stowlin on here also has a solar set up. Pretty common on sailboats and some trawlers. 

there are a number of websites that will help you with the calculations and help you determine what you need. Remember to calculate amp hours, not just total amps. Your fridge may run 4amp an hour but over 20 hours, your looking at 80 total. You need to match you power input to that level as well as your battery capacity. 

If you have’s already, I’d recommend you start changing out all your lights, etc with LED to reduce the load.


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## acidMia (Aug 3, 2016)

It's a powerboat, twin inboard. The interior lights have all been switched to LED. I still have some outstanding nav lights to switch over. 
(I dont like the LED interior lights and dont use them much tbh and am currently in the middle of ripping everything apart so maybe I can find better replacements but thats another story)

Noted for deep cycle batteries. I'm not sure what I currently have re: AGM or wetcell. They seem to work well enough. Is it bad practice to mix the two? If I leave the current two for the engines, and replace the house with proper AGM deep cycle for the other stuff?

Going to look up calculator sites now


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## Chiefster23 (Feb 5, 2016)

Mia. There are quite a few members here with off grid solar power systems, including me. Some guys are very knowledgeable. Not many folks are online today as this is the first day of new software. Also, the ‘search’ function isn’t fully up to speed yet. Keep coming back and wait a couple days and do a ‘search’. About two years ago I did a series of posts about how I started with a small solar kit and expanded it over time to 1000 watts of panels and 700 amp hrs of batteries. Over time I’m pretty sure you can get 99% of your questions answered here. You just picked a bad time to start today with the forum change over. Stick with us. We will help.


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## acidMia (Aug 3, 2016)

I thought I must be going mad when not many results turned up  Thanks for the explanation. I'll check back for that.


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## Piratesailor (Nov 9, 2012)

acidMia said:


> It's a powerboat, twin inboard. The interior lights have all been switched to LED. I still have some outstanding nav lights to switch over.
> (I dont like the LED interior lights and dont use them much tbh and am currently in the middle of ripping everything apart so maybe I can find better replacements but thats another story)
> 
> Noted for deep cycle batteries. I'm not sure what I currently have re: AGM or wetcell. They seem to work well enough. Is it bad practice to mix the two? If I leave the current two for the engines, and replace the house with proper AGM deep cycle for the other stuff?
> ...



Yes, don’t mix wet cell and AGM/Gell cell batteries.


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## stowlin (Apr 25, 2016)

You are hoping to get to 60 amp? That’s a bunch and IDK how big your boat is but that might take a whole lot more then most boats can handle. Batteries are heavy so get light thin panels they do cost more but do you need more watts in the sun or other gear. Also I like the thin panels because I can put them on either side of the cabin for the best sun and move them often. I keep a 60 below too in case SHTF and I lose my 200 watts on deck. Inverters are affordable and impossible to fix so get two.


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## acidMia (Aug 3, 2016)

60 amps is a lofty goal. The more I learn about what it all takes, the less likely I think I'll get there haha.


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## Weldman (Nov 7, 2020)

Captainrich said:


> ok, what kind of boat are we talking about?
> 
> First, you can tie in solar panels to the existing system onboard. Most panels put out DC current at 12 volts +- .
> It will act like a trickle charger, replenishing the electricity in the batteries as needed.
> ...


Please don't or you will regret this later, tying in batteries with old batteries (existing system onboard) will drag new batteries down and only go as high in AH as the lowest AH rating battery.
In theory yes the 200 watts at 12 volts will give you 8.333 amps to charge up a 800 amp battery in 100 hours of sunlight but then that is if you are talking 800 AH worth of batteries which you would need C10 to keep that battery alive which equates to 80 amps at 12 volts going in to recharge it properly. Which I highly doubt you are talking AH on the batteries you are talking cranking amps which is not what you go by when getting solar panels.
If you want to do this right keep the solar batteries separate from existing system of batteries so as they don't drag each other down and put a solenoid between the two so electricity flows one way when running boat engines.
Deep cycle will last you about a year or two, 6V GC2's Golf Cart batteries will last you 3 to 5 years, Group 903's AKA L16's will last you 5 plus years and so on and if you got money to spend lithium is what you want which average about $1,000 for every 100AH

Lastly DON"T hook up any solar panels to your batteries via alligator clips, that's against ABYC codes (American Boat Yatch Club) or Coast Guard regulations and could ignite hydrogen sulfide fumes or gasoline fumes, in fact learn through ABYC codes on how wiring is done and you will have almost perfect way of setting up a photovoltaic system (solar system). You will learn ANCOR is your friend with majority of marine products in doing solar. Anyone got any bourbon, my glass is empty, maybe next drink I will explain more if you want to learn more and I will help by posting on others replies/threads.


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