domestic grid solar panel to charge 12v dc

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Chris1234
Chris1234 Registered Users, Users Awaiting Email Confirmation Posts: 2 ✭
in Solar Beginners Corner #1
I have an  older timber cruiser, perminantly moored which requires intermittent use of a bilge pump. I have  a few bilge pumps for reliability and backup, but the basic power system on the boat is powered by a single N70 12v battery. I currently have an older Solarex  40w panel which has lost capacity and needs replacement. 
However, I do have some 190w x 48v domestic grid panels surplus after upgrading my home grid system and was wondering if I could use a transformer to drop the voltage or do I need a specialized controller?
Perhaps not possible at all...
I have reasonable 12v knowledge, but not up to date with full electronic and electrical jargon.
It seems silly to pay for a new 12v panel if I can convert a 48v panel at minimal cost
Thanks


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  • Photowhit
    Photowhit Solar Expert Posts: 6,017 ✭✭✭✭✭
    edited August 2020 #2
    You can use a MPPT type charge controller to drop the voltage and correctly charge your battery bank.

    They are NOT inexpensive. Seems I heard recently of a couple other marine sealed charge controllers, but I would generally recomend a Midnite Solar Kid inverter.

    MidNite Solar The Kid Marine MPPT Solar Charge Controller in Black
    https://www.solar-electric.com/midnite-solar-kid-marine-mppt-solar-charge-controller-black.html

    Charge controllers are rated at output amperage, so you might want too use Midnites's string sizing tool to figure out how many panels you could put on it.

    https://midnitesolar.com/sizingTool_kid/index.php
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Chris1234
    Chris1234 Registered Users, Users Awaiting Email Confirmation Posts: 2 ✭
    #3
    Thanks ill check it out
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    you CAN use a simple PWM charger with your 48V panels. but the charger must be rated to the Voc of the panels.  You will not get the full  190 w , but only will harvest the amps the panel can produce.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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