domestic grid solar panel to charge 12v dc

Chris1234Chris1234 Registered Users, Users Awaiting Email Confirmation Posts: 2
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


  • PhotowhitPhotowhit Solar Expert Posts: 5,830 ✭✭✭✭✭
    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

    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.
    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, 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.
  • Chris1234Chris1234 Registered Users, Users Awaiting Email Confirmation Posts: 2
    Thanks ill check it out
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    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

    gen: ,

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