Very new to solar, question about my controller and system!

cg52cg52 Registered Users Posts: 1
I recently purchased an off-grid cabin with (what I think is) a 12 volt solar system in place.  It has 2 batteries in the battery bank and a "Thunderbolt Magnus Solar 4 amp, 12 volt charge controller."  There are panels outside wired in - no inverter.  Throughout the summer the reader always was between 11 - 12.4.  Now, in the winter (I'm in Seattle) there is nothing on the display at all.  Despite this, we still have some power - using the lights at night.  Only once or twice did they dim or go out.  

I am VERY new to this, and get lost easily in numbers and jargon.

Any ideas on what's going on with my system?  Do I need a new battery or two?  Should I add a couple of batteries?
Any (basic, layman's terms) insight is welcomed.  I'm trying to read up on everything, but am pretty busy with work -- studying after a long day is proving difficult.

Thanks in advance.


  • vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
    Welcome to the forum.

    Your batteries are dead.  Before you replace them, we should figure out whether the system can supply your needs.  If you are running an energy deficit, buying new batteries will be a waste of money because they will die young.

    You're in Seattle?  I've never been there, but I hear there are some clouds... do you have a generator to charge the batteries when it's cloudy?

    You need to define what you want from this system... Just DC lights? Are they LED lights?  How many watts do they draw, and for how many hours per day?

    When you know how many watthours of energy you use per day, then you can properly choose a battery that can handle the load.  After the battery is chosen, you need to have enough resources (solar or generator) to keep the battery happy.  Being off grid is really all about the battery.

    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    As vt said youve come to the right place. Because solar systems are not like cars (any old car will probably get you from a to b), in your situation the best thing is do a fresh paper design, as if were starting from scratch.

    The things we need to do that are:
    -  make a list of all the gear. (size, number brand and/or specs) For the panels you might need to remove one to examine the sticker underneath. (1 or 2 photos of the wiring, fusing, batterys and controller would be a bonus).
    - as vt said make a list of all the things you want to run, and for how long on each "average" day. For example:

       One 30W laptop for 3 hours  equals 90 Watt hours per day.
       Three 6W LED bulbs for 5 hours per day equals 30Wh/d. (Ie: use, watts, and hours. )
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,

  • littleharbor2littleharbor2 Solar Expert Posts: 1,628 ✭✭✭✭
    Thunderbolt 4 amp controller tells me you likely have a Harbor Freight 45 watt 3 panel, or equivalent, array. Couple that with Seattle in the winter and you won't be making enough power to keep a AA battery charged. These low quality solar "kits" usually don't last for more than 4-5 years before burning out. Sounds like your battery bank is shot as well.

    If you still want to have a small off grid solar set up your best bet is to scrap the whole thing and start new with some better quality components.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

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