29V panel with 12V bank?

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System
System Posts: 2,511 admin
in General Solar Power Topics #1
I believe I know the answer to this but would like to confirm before committing cash.

I will be installing a panel on the sailboat I am finishing up. The bank is four L16HCs with total capacity of about 840 AH @ 12V. For structural reasons I want to use only one panel so I would like to use a 220 watt with a 29V MPV. Can I use a MPPT for charging and if so do I loose a lot in efficiency?
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    #2
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    Re: 29V panel with 12V bank?

    You're fine with MPPT controller.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: 29V panel with 12V bank?

    i guess you know that the output you'll get from 1 220w pv will be too small to charge the 840ah battery bank with.:confused: trojan recommends a 10% rate to their batteries, which would be 84 amps one would need to give the batteries a factory recommended charge. that 1 pv will deliver about 1.5% which is fine for a float charge or offsetting the daytime draw of loads by the amount of power the pv can deliver.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: 29V panel with 12V bank?

    But know in advance that one 220 Watt panel isn't going to do much for an 840 Amp hour battery bank.
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #5
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    Re: 29V panel with 12V bank?
    But know in advance that one 220 Watt panel isn't going to do much for an 840 Amp hour battery bank
    Being a sailboat, the OP probably has multiple charging sources hopefully. Shore power charger of at least 100 amps, 130 amp alternator on engine, possibly wind charger, etc. Still if there is room, I would create a bimini with about 4 panels for that size battery bank.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
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    Re: 29V panel with 12V bank?
    mikeo wrote: »
    Being a sailboat, the OP probably has multiple charging sources hopefully. Shore power charger of at least 100 amps, 130 amp alternator on engine, possibly wind charger, etc. Still if there is room, I would create a bimini with about 4 panels for that size battery bank.

    Yes indeed, Mike!
    Too often we see people with insufficient panel capacity wondering why their batteries gave up the ghost a few years too early. It's just one of those cautions that has to be said: don't expect a 2% charge rate to do the whole job.
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  • System2
    System2 Posts: 6,290 admin
    #7
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    Re: 29V panel with 12V bank?

    Thanks all. I am limited to a single panel due to the design of the Bimini frame. The panel has to be on the back half to avoid shading from the mainsail and boom and I want to be reasonably easy to dismount in case of really bad weather.

    The panel will be primarily just for float and to help maintain base loads like refrigeration and anchor light (est (80ah/day) when we are off the boat. Primary charging is a 240 amp low RPM emergency vehicle alternator. The goal is to cycle the batteries between 60% and 85% on a 48 hour charging cycle.
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