Newbie looking to spec solar system for 12v sailboat

oomfh
oomfh Registered Users Posts: 1
in Solar Beginners Corner #1
Have a smaller (25') sailboat. Currently operate running and interior lights, small fan, instruments, MP3 player and VHF radio.

Outboard has electric start and alternator - but I am excluding that since it is used minimally.

Currently have a single Grp 27 battery which works fine for weekends. Would add a second (same spec) battery for an extended trip.

Since this is a pretty minimal system, I'm not too concerned about cost - it's more about reliability and quality.

Panel will be hung off the rear of the boat so there will be no shadows cast from rigging.

I'm strongly leaning toward monocrystalline and MPPT.

I'm looking for specs for a panel, controller and monitor.

Any advice would be greatly appreciated!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Newbie looking to spec solar system for 12v sailboat

    Welcome to the forum.

    A single Group 27 battery is usually around 90 Amp hours, so it doesn't take too much to charge it. Even less to maintain one. If you double up the battery it takes twice as much of course.

    In panel Watts you're looking at 150 or so for one battery with a PWM charge controller.
    For two batteries and using an MPPT type controller, about 280 Watts.

    This is assuming the battery capacity and a desire for 9 Amps per battery to charge. It is important to know the battery capacity, otherwise the numbers could be way off.
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  • AuricTech
    AuricTech Solar Expert Posts: 140 ✭✭
    #3
    Re: Newbie looking to spec solar system for 12v sailboat

    Given both the relatively small size of your planned battery bank and your requirement for a battery monitor, along with Marc's comments about the likely size of your PV panel needs, you might be best served by purchasing something along the lines of these components:

    For your planned application, a PV system using an MPPT charge controller and grid-tie PV panels would likely cost more than one using a PWM charge controller and PV panels designed to charge a 12V battery bank.

    ETA: If you have room for it, you might be better served by replacing your present Group 27 battery with a single 4D battery (such as the UPG 200 Amp-hour AGM battery), rather than adding another Group 27 battery to your bank. Replacing your current Group 27 battery with one 4D battery would help you avoid issues that can arise from either matching batteries of different ages in one bank or connecting batteries in parallel.

    ETA 2: If you decide to go with the 4D battery option I mentioned above, you'll likely need to upgrade your planned PV array to somewhere around 400W rated.
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  • TucsonAZ
    TucsonAZ Solar Expert Posts: 139 ✭✭
    #4
    Re: Newbie looking to spec solar system for 12v sailboat

    I'm pretty certain the little Rogue MPT-2024 MPPT can handle one 250 watt grid tie panel and charge the batteries at 12v which would be my choice. If you get a grid tie panel you should be able to get a 280w panel for under $200 if you look around and can buy locally, I know the Chaori panels can be commonly had for under $0.75 a watt. So that would be $200 for the panel, $250 for the charge controller and that would give you a good system that would take care of all your needs.

    If you went 12v panels, you'd be looking at three 100 watt panels which would be $360 alone based on the lowest prices I've been able to find and you'd still have to buy a charge controller.

    Mono/poly really just depends on your location, needs, and uses, being in AZ I'm better off with poly as they do better with the heat than monos, focus more on price per watt.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Newbie looking to spec solar system for 12v sailboat
    TucsonAZ wrote: »
    Mono/poly really just depends on your location, needs, and uses, being in AZ I'm better off with poly as they do better with the heat than monos,

    There is no reason to think that; the materials involved are identical and there's no significant difference in temperature coefficient between the two types.
    focus more on price per watt.

    That is for sure. However in any mobile application (or other space-limited system) the slightly higher efficiency of the mono panels may be worth the premium price.
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